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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Very-low-fat diets are superior to low-carbohydrate diets: evidence shows
that very-low-fat diets (not low- or moderate-fat diets) may be easier, not harder, to follow and make more sense physiologically. They should also produce the best weight loss and health outcomes in the long run.(VIEWPOINT). Daniel S. Kirschenbaum. Patient Care 39.11 (Nov 2005): p47(7). For more than half a century, millions of Americans have periodically followed diets that were very low in carbohydrates (and high in protein and fat) in search of the best and easiest way to lose weight. The late Robert C. Atkins' 1998 revision of his 1972 Dr. Atkins' Diet Revolution was on the New York Times best-seller list for more than 6 years, and many other best-sellers have advocated similar low-carbohydrate diets. (1) Several professional organizations, including the American Dietetic Association (ADA) and the American Heart Association (AHA), have advised against the use of low-carb diets because considerable scientific evidence suggests that diets like these may promote cardiovascular, kidney, and liver diseases, as well as cancer. (2) Despite the ostensible health risks of low-carb diets, some people have followed this approach and lost weight. This anecdotal evidence, coupled with successful marketing campaigns, has led even neutral consumer advocates to encourage weight controllers to "add a little fat" to their diets. (3) Despite waning interest in this approach, acceptance of the supposed benefits of low-carb dieting still appears routinely in the media and is evident in restaurant menus and on supermarket shelves. Only a careful review of the scientific literature can determine whether health professionals should recommend or oppose low-carb dieting for their confused overweight patients. Bravata et al recently identified 2616 articles in professional journals (including 94 empirical studies) pertaining to the efficacy of low-carb dieting. (2) However, only 6 studies--5 of them published since the Bravata review was completed--have compared low-carb/moderate- to high-fat diets with diets described as "low-fat" using random assignment and evaluations lasting at least 6 months. (4-10) The authors of 4 of these 6 studies concluded that their low-carb diets helped their overweight participants lose more weight than their low-fat diets. (4,6,7-9) A critical review of these studies, however, reveals that none provides scientifically valid evidence for this claim. This article presents the basis for this assertion and provides an empirically grounded rationale for recommending very low-fat diets. Flaws in research designs Three major flaws in research designs undermine the validity of these studies. First, all 4 of the studies that found some ostensible benefits for low-carb diets used elaborate intervention programs (for example, 18 months of weekly sessions), not dietary instructions alone. (4,6,7-9) Including the diets within extensive programs confounds the integrity of the independent variable, decreasing internal validity ("diffusion of treatment") and external validity ("multiple treatment interference"). (11) Second, the administrators of these diet/behavioral programs had far more opportunities for their beliefs or biases to have an impact on outcomes than they would have had in a study, like that of Foster et al, that used a diet intervention alone. (5) This raises possibilities of investigator and experimenter bias that threaten both internal and external validity ("reactivity of experimental arrangements" and "combination of experimental setting and treatment"). (11) Two of the 4 studies that supported the supposed differential benefits of low-carbohydrate diets were funded by companies (olive oil and peanut companies and The Dr. Robert C. Atkins Foundation) that had--and still have--major financial allegiances to low-carbohydrate diets. (6,8) This fact clearly increases the salience of concerns about investigator/experimenter bias, although it by no means impugns the integrity of the researchers. The third design flaw is the most important: None of the 4 studies that ostensibly found benefits for low-carb diets used a truly low-fat diet (for example, 5%-10% of calories from fat), sometimes referred to as a very-low-fat diet. Thus, these studies actually compared low-carb diets with moderate-fat diets (goals were 20%, (6) 25%, (5) and 30% (4,7,8) of calories from fat; obtained: 29%-33%), thereby creating a "construct validity" problem. (11) When is a diet a diet? Only Foster et al tested the relative efficacy of a diet per se, as it is usually attempted by the millions of people who buy diet books. (5) This study also yielded no differences between low-carb and low-fat diets at a 1-year follow-up and produced about half the weight loss in their best group, as compared with the best group of 2 of the other studies. (4,8) The remaining studies tested dietary instructions within educational and behavioral programs. Professionally conducted weight-control programs are far more likely to help people lose weight than self-help approaches. (12) In fact, a meta-analysis showed that the single best predictor of weight loss is length of treatment. (13) Longer treatments also produced much more weight loss in studies that experimentally compared longer to shorter treatments. (14) These effects of amount of contact with professionals emerge almost regardless of the content that is focused on within the sessions. (15) Apparently, participation in such programs helps weight-controllers set goals, monitor and evaluate their behaviors, and generally stay motivated, optimistic, and focused on change. These findings indicate that the 5 low-carb studies under consideration here that embedded the diets within educational/behavioral programs must attribute some of their effects to the programs themselves, not the diets. Investigator and experimenter bias Investigators' hypotheses can intentionally or unintentionally affect the manner in which the experimental protocol is specified and delivered and the accuracy of data gathering and analyses. Similarly, experimenters (in these studies, dietitians) can affect recruitment and retention of participants. [GRAPHIC OMITTED] In the present set of studies, the researchers and dietitians probably knew that publication, notoriety, and subsequent funding may have depended on finding benefits for low-carb diets. The enthusiasm of the dietitians who administered the programs could have varied according to condition, quite possibly unintentionally, thereby affecting attrition and recruitment for evaluations. In fact, the attrition in some of the low-fat groups was as much as 400% higher than the usual attrition rate for related behavioral programs that used low-fat or very-low-fat diets (80% versus 20%) and was significantly higher in low-fat compared with low-carb groups in 3 of the 6 studies. (6,7,8,15) This suggests the possibility of differential enthusiasm for the treatments. Research on investigator and experiment bias has revealed some dramatic effects, including studies showing that experimenters' computational errors favor investigators' hypotheses 75% of the time. (16) The authors of the 2 studies under review here that received financial support from companies with vested interests in low-carbohydrate diets based their conclusions favoring low-carb/moderate-to-high fat diets on potentially flawed analyses. (6,8) First, the "primary analyses" of McManus et al were conducted using a "low-fat" group in which 67% (20 of 30) subjects analyzed had dropped out of the program. (6) Thus, they almost certainly were no longer following the low-fat approach when they were counted as "low-fat" dieters. This group was compared with a higher-fat group comprising 25 active participants and only 6 dropouts. Forty additional dropouts were not "available for measurements." Based purely on research showing the powerful impact of active participation in weight-loss programs, 67% of the low-fat group included in the primary analyses would be expected to fare poorly, compared with 19% of the low-carb group. (13) This differential subject attrition, one of the primary threats to internal validity, was statistically very significant (P .001) but ignored by the authors. When the researchers compared only current participants (excluding dropouts), the groups did not differ in weight loss. The quality and outcomes of the manipulation checks in the study by Yancy et al raise questions about the nature of the independent variable (the distinctiveness and characterizations of the diets). (8) The Atkins' (low-carb) diet group was instructed to consume less than 20 g/d of carbohydrates--a severely restricted level of carbohydrate consumption. The authors noted that carbohydrate consumption under 40 g/d (twice the allowed level) should have been readily detected by urinary dipstick tests. However, only 19 of 59 (32%) participants included in analyses had observed trace levels of ketones. Since the vast majority of those assigned to the low-carbohydrate diet failed to restrict their carbohydrate consumption enough to be detected at twice the allowed level, it seems problematic to consider this group to be a "low-carbohydrate diet group." Perhaps the researchers considered their dietary assignments to be successful based on analyses of the diets reportedly consumed by participants. Unfortunately, only 20 out of 119 (17%) of participants were selected (not randomly assigned: 13 low-carb dieters, 7 low-fat dieters) for analyses of their diets. No measure of the reliability of these dietary assessments was reported. Even if participants had followed Yancy et al's dietary manipulation exactly as intended, these researchers, like McManus et al, largely ignored the potential impact of differential subject attrition. (6,8) The Yancy study did not acknowledge the McManus study or others showing that dropouts often fail to lose weight, compared with those who stay in treatment. (13,15) The McManus and Yancy low-fat participants prematurely discontinued treatment almost twice as often (43%) as their low-carbohydrate groups (24%). Unlike McManus et al, however, Yancy et al did not analyze the data separately for completers only. Without taking into account the likely poorer performance of the greater number of dropouts in the low-fat group, Yancy et al may have inadvertently skewed the results in favor of their low-carbohydrate group. Furthermore, the use of linear mixed-effects models to project expected weight losses (instead of analyzing the data actually obtained) may have capitalized on the well-known effect of low-carbohydrate diets to produce initially greater weight losses. (9) Also, as Yancy et al noted, their use of projected values depended on the assumption that including dropouts would not affect the meaning of the results ("noninformative dropouts"). In weight-control research, however, dropouts lose less weight than completers. (13,15) Therefore, including these dropouts "informed" the outcomes, thereby perhaps violating an assumption of the analyses. This argument gains support by calculating the impact on the results of including the dropouts. The low-carbohydrate dieters were projected to lose 85% more weight than those assigned to the low-fat group at the 24-week point. When dropouts are deleted from these projections (counting them as losing no weight in both diet conditions), the discrepancy between groups decreases substantially. The projected difference decreases by 236% (from 85% to 36%), quite possibly rendering the actual differences between groups nonsignificant. When is a low-fat diet a low-fat diet? The biggest problem in the studies that supposedly favored low-carb diets was the failure to use truly low-fat diets. Samaha et al used a moderate-fat goal, 30% calories from fat, in their "low-fat" group. (7) They reported a baseline level of fat consumption by that group of 33% of calories from fat (68 g/d) and even after "six months of dietary counseling," this group averaged the same percentage of calories from fat (33%; 57.8 g fat). Data in McManus et al also showed minimal changes and moderate levels of fat consumption at baseline (31%) and follow-up (30%) in the low-fat group. (6) Brehm et al and Yancy et al used low-fat goals of about 30%, and they both reported 29% fat consumption during the program. (4,8) In their extensive review of the efficacy of popular diets, Freedman et al categorized the level of fat consumption obtained in these 4 studies as "moderate-fat." (16) Current evidence suggests that the moderately high levels of fat consumption achieved in these studies should not have helped weight-controllers succeed. (17,18) In a review of dietary interventions, Barnard et al reported that "only very stringent dietary manipulations led to effective change." (19) They found that the 3 studies that clearly produced the greatest changes in diets limited "dietary fat to no more than 10% of energy," not the 25% to 30% of calories from fat used by almost all of the other 27 studies in their review and obtained (29%-33%) by the studies under discussion here. Freedman et al also asserted that "data support the contention that those consuming low-fat, low-calorie diets are most successful in maintaining weight loss." (16) Stice's survey of 396 adolescents also illustrates the differential benefits of very-low-fat compared with low/moderate-fat diets. (20) He found that only those who followed a very stringent approach lost weight; those who reported following more moderate diets actually gained weight. Weight-controllers in Jeffery et al also found a low-fat approach easier to use and more palatable than a calorically restricted diet without limits on fat. (21) (It's easier to eat no potato chips at all than just one.) The data from both these studies and the Barnard et al review support Barnard's conclusion: "Higher limits on fat intake, which may be selected in hopes of maximizing the acceptability of prescribed diets, may actually discourage a greater degree of dietary change." (19) Lowering levels of fat consumption is crucial [GRAPHIC OMITTED] Other analyses of the impact of macronutrients on weight change support the view that moderate (and certainly high) fat consumption can inhibit weight loss and maintenance of reduced weight. The extensive review of the efficacy of low-carb diets in Bravata et al showed that "among obese patients, weight loss was associated with longer diet duration, restriction of caloric intake, but not with reduced carbohydrate content". (2) The Freedman et al review also found no support for the benefits of reducing carbohydrate content, without restricting calories, on weight loss. (16) For example, Harris et al studied 157 weight-controllers over 18 months and found that reducing the percentage of calories from carbohydrates (and protein) did not affect weight loss. (22) In contrast, eating very little fat, and specifically minimizing consumption of beef, hot dogs, and sweets, did predict weight loss (as it did in Holden et al). (23) Reducing calories from fat actually predicted weight loss even better than change in total calories (as it did in Jeffery et al). (21) In a remarkably similar vein, but with children as the focus, Gazzaniga and Burns found that a group of obese children ate much more fat and many fewer carbohydrates than their lean peers. (24) Even after statistically adjusting for total energy intake, physical activity, and metabolic rates, obese children still ate more fat and fewer carbohydrates. As would be expected from these results, highly successful adult weight-controllers consume much less fat than average Americans and about 10 times the level of carbohydrates recommended by Atkins. (25) Weight-loss programs that counsel people to eat like this have produced among the most promising outcomes in long-term evaluations. (26) Animal and physiologic research also supports the benefits of truly low-fat diets compared with moderate-fat diets. Several studies showed that animals fed high-fat diets gained weight much more readily than those fed diets much lower in fat. (27) Boozer et al also found that high-fat diets not only promote weight gain but also inhibit weight loss. (28) They compared several groups of rats whose food was restricted to 75% of the calories in their baseline diets. The rats that were fed high-fat, restricted-calorie diets (45% fat) failed to lose weight, compared with rats that consumed diets of the same restricted calorie level that were moderately high in fat (28%) and low in fat (12%). Three human studies also found that much-lower-fat diets resulted in weight loss even when total calories were not reduced, an effect never obtained with low-carb diets. (16) Bessesen et al demonstrated a method through which high-fat diets inhibit weight loss. (29) They found that when obese rats consumed dietary fat, it was transported to storage in fat cells and away from muscle cells much more so than was the case in lean rats. This pattern was accentuated for formerly obese rats. Formerly overweight people also show a differential sensitivity to fat at the cellular level. (30) They may also have greater physiologic sensitivity (insulin secretion, salivation) to the presence and even the thought of highly palatable high-fat food. (31) Consuming high-fat foods may also encourage overeating by increasing appetite and decreasing satiety to a greater extent than low-fat foods. (32) This may occur because eating such foods may stimulate the endogenous opioid peptide system. Consuming a high-fat diet also induces heightened sensitivity to leptin, leads to increases in ghrelin, and inhibits the transportation of insulin into the brain, all of which probably increase eating and weight gain. (16) In fact, a recent study showed that a very low-fat/high-carbohydrate diet (15% calories from fat, 65% carbohydrate, 20% protein) failed to trigger the type of increase in ghrelin (a potent orexigenic signal) that is typically seen when people lose weight by restricting calories in higher-fat diets. (33) Why were truly low-fat diets not used in these studies? This evidence raises questions about why these researchers chose "low-fat" dietary levels (actually "moderate-fat" diets, according to Freedman et al) that were 50% to 100% higher than genuinely "low-fat" or "very-low-fat" levels. (16) Part of the answer is that the current evidence, while compelling, remains somewhat controversial and circumstantial. Definitive treatment outcome studies that clearly favor very-low-fat diets have not yet emerged, although the evidence certainly points in that direction. The reliance on tradition (actually, myths) provides another explanation. For decades, major professional groups that focus on diet and health (such as the AHA and ADA) have advocated moderation as the key to success in weight control. Extreme approaches, or so the myth goes, will not work because they induce feelings of deprivation and binge eating. Yet, the scientific evidence shows that more stringent goals for fat consumption seem easier (not harder) to implement consistently, make more sense physiologically, and produce the most promising results. Implications Perhaps the greatest irony in the current low-carb craze pertains to the overwhelming scientific evidence showing that self-help and other minimal interventions (for example, diet books and instructions alone) rarely help people lose much weight. Yet, publications in prestigious journals with favorable editorial commentaries, public relations campaigns, anecdotal claims, sales of millions of books, and countless stories in the media have prompted literally thousands of papers addressing this issue. (2,16) It is time for diet to be put in its place. A diet is just one element that can facilitate weight loss only when weight-controllers sustain major efforts to transform their lifestyles (activity level, stress management, focusing, and commitment). Furthermore, even when extracting the contribution of diet on weight loss, the possible long-term risks of low-carbohydrate/high-fat diets and some noteworthy short-term adverse effects (such as significantly increased GI distress, headaches, and muscle weakness) should discourage the use of such diets. (8) Unless valid scientific research shows reliable and differential weight loss and other benefits for low-carb diets, which seems unlikely at this juncture, the recommended pathway to successful weight control should include a very-low-fat diet, not a low-carb/high-fat diet. This article was contributed by Dr Kirschenbaum and edited by Peter D'Epiro, PhD. Dr Kirschenbaum discloses that he is Clinical Director and Chief Program Officer, Healthy Living Academies Division of Aspen Education Group, Cerritos, Calif. www.patientcareonline.com Visit our Web site for * Quick access to the reports and Internet resources discussed in these pages REFERENCES 1. Atkins RC. Dr. Atkins' New Diet Revolution (Revised and Updated). New York, NY: Avon Books; 1998. 2. Bravata DM, Sanders L, Huang J, et al. Efficacy and safety of low-carbohydrate diets: a systematic review. JAMA. 2003;289:1837-1850. 3. The truth about dieting. Consumer Reports. 2002;67:26-31. 4. Brehm BJ, Seeley RJ, Daniels SR, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrin Metab. 2003;88:1617-1623. 5. Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-carbohydrate diet for obesity. New Engl J Med. 2003;348:2082-2090. 6. McManus K, Antinoro L, Sacks F. A randomized controlled trial of a moderate-fat, low-energy diet compared with a low fat, low-energy diet for weight loss in overweight adults. Int J Obesity. 2001;25:1503-1511. 7. Samaha FF, Iqbal N, Seshadri P, et al. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 2003;348:2074-2081. 8. Yancy WS, Olsen MK, Guyton JR, et al. A low-carbohydrate ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia. Ann Intern Med. 2004;140:769-777. 9. Stern L, Iqbal N, Seshadri P, et al. The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial. Ann Intern Med. 2004;140:778-785. 10. Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005;293:43-53. 11. Cook TD, Campbell DT. Quasi-Experimentation: Design and Analysis Issues for Field Settings. Chicago, III: Rand McNally College Publishing Company; 1979. 12. Heshka S, Greenway F, Anderson JW, et al. Self-help weight loss versus a structured commercial program after twenty-six weeks: a randomized controlled study. Am J Med. 2000;109:282-287. 13. Bennett GA. Behavior therapy for obesity: a quantitative review of selected treatment characteristics on outcome. Behav Ther. 1986;17:554-562. 14. Baum JG, Clark HB, Sandler J. Preventing relapse in obesity through post treatment maintenance systems: comparing the relative efficacy of two levels of therapist support. J Behav Med. 1991;14:287-302. 15. Kaplan RM, Atkins CJ. Selective attrition causes over estimates of treatment effects in studies of weight loss. Add Behav. 1987;12:297-302. 16. Freedman MR, King J, Kennedy E. Popular diets: a scientific review. Obes Res. 2001(suppl 1):1S-40S. 17. Perri MG, Nezu AM, Viegener BJ. Improving the Long-Term Management of Obesity: Theory, Research, and Clinical Guidelines. New York, NY: John Wiley & Sons; 1992. 18. Barber TX. Pitfalls in Human Research: Ten Pivotal Points. New York, NY: Pergamon Press; 1976. 19. Barnard ND, Akhtar A, Nicholson A. Factors that facilitate compliance to lower fat intake. Arch Fam Med. 1995;4:153-158. 20. Stice E. Prospective relation of dieting behaviors to weight change in a community sample of adolescents. Behav Ther. 1998;29:277-297. 21. Jeffery RW, Hellerstedt WL, French SA, et al. A randomized trial of counseling for fat restriction versus calorie restriction in the treatment of obesity. Int J Obesity. 1995;19:132-137. 22. Harris JK, French SA, Jeffery RW, et al. Dietary and physical activity correlates of long-term weight loss. Obes Res. 1994;2:307-313. 23. Holden JH, Darga LL, Olson SM, et al. Long-term follow-up of patients attending a combination very-low calorie diet and behaviour therapy weight loss programme. Int J Obes. 1991;16:605-613. 24. Gazzaniga JM, Burns TL. Relationship between diet composition and body fatness, with adjustment for resting energy expenditure and physical activity, in preadolescent children. Am J Clin Nutr. 1993;58:21-28. 25. Shick SM, Wing RR, Klem ML, et al. Persons successful at long-term weight loss and maintenance continue to consume a low-energy, low-fat diet. J Amer Diet Assoc. 1998;98:408-413. 26. Wadden TA, Foster GD, Letizia KA, et al. A multicenter evaluation of a proprietary weight reduction program for the treatment of marked obesity. Arch Intern Med. 1992;152:961-966. 27. Salmon DMW, Flatt JP. Effect of dietary fat content on the incidence of obesity among ad libitum fed mice. Int J Obes. 1985;9:443-9. 28. Boozer CN, Brasseur A, Atkinson RL. Dietary fat affects weight loss and adiposity during energy restriction in rats. Am J Clin Nutr. 1993;58:846-852. 29. Bessesen DH, Rupp CL, Eckel RH. Dietary fat is shunted away from oxidation, toward storage in obese Zucker rats, Obes Res. 1995;3:179-189. 30. Tremblay A, Despres JP, Bouchard C. Adipose tissue characteristics of ex-obese long-distance runners. Int J Obes. 1984;8:641-648. 31. Johnson WG, Wildman HE. Influence of external and covert food stimuli on insulin secretion in obese and normal persons. Behav Neurol. 1983;97:1025-1028. 32. Blundell JE, Cotton JR, Delargy H, et al. The fat paradox: fat-induced satiety signals versus high fat overconsumption. Int J Obes. 1995;19:832-835. 33. Weigle DS, Cummings DE, Newby PD, et al. Roles of leptin and ghrelin in the loss of body weight caused by a low fat, high carbohydrate diet. J Clin Endocrinol Metab. 2003;88:1577-1586. DANIEL S. KIRSCHENBAUM, PhD Clinical Director and Chief Program Officer, Healthy Living Academies Division of Aspen Education Group, Cerritos, Calif; Director, Center for Behavioral Medicine & Sport Psychology; and Professor of Psychiatry and Behavioral Sciences, Northwestern University Medical School, Chicago, Ill. His most recent book is The Healthy Obsession Program: Smart Weight Loss Instead of Low-Carb Lunacy (http://www.benbellabooks.com). RELATED ARTICLE: Article at a glance ** Five studies published in the past 3 years compared low-carbohydrate to low-fat diets using random assignment and evaluations lasting about 6 months or longer. ** The authors of most of these studies concluded that their low-carb diets helped their overweight participants lose more weight than their low-fat diets. ** A critical review, however, reveals that none of these studies provides valid evidence of the differential effectiveness for weight control favoring low-carb diets. ** This analysis provides an empirically grounded rationale for recommending truly low-fat diets for weight loss, unless and until valid evidence suggests otherwise. Low-carb Sample Menu Breakfast Cheese-baked eggs Sausage patties Tea or decaf coffee with cream and sugar substitute Lunch Chicken croquettes on a bed of lettuce Sugar-free orange gelatin parfait Dinner Sour cream clam dip with fried pork rinds Fennel red snapper Tossed green salad with creamy dijon vinaigrette dressing Tea or decaf coffee with cream and sugar substitute Snack Vanilla ice cream Low-fat Sample Menu Breakfast Egg white omelet with red potatoes, fat-free cheese, diced onion, and garlic Nonfat blended berry yogurt Berries Herbal tea or coffee with skim milk and sugar substitute Lunch Pepperoni pita pocket pizza (fat-free pita bread, pizza sauce, soy pepperoni, fat-free shredded jack and cheddar cheese) Low-fat split pea or vegetable soup Iced tea or diet soda Dinner Broiled lobster with lemon Roasted new potatoes Asparagus Salad with fat-free dressing Fruit salad and frozen sorbet or yogurt Hot herbal tea or diet soda Snack Pretzels, low-fat popcorn, or whole fruit |
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Roger Zoul wrote:
Snip article... There is nothing surprising here. It just goes to support that the core of all successful diets is calorie deficit. An extremely low fat diet would lower calories quite successfully, fat containing more calories than carbs. The point isn't what type of diet, it is the ability to sustain whatever diet is chosen, along with the supply of sufficient nutrients to ensure good health. I lost a lot of weight while eating large and satisfying meals simply by choosing my foods carefully (lowering unecessary carbs in my case, but not to ketonic levels) and increasing both the frequency and degree of exercise in my life. Not just gym, but including pleasurable pastimes that require exertion. I see the real problem as being a very definite reluctance on the part of the majority of overweight people to incorporate sufficient exercise. They all want an *easy* weight loss program. Diets don't need to focus on any particular calorie source, they just need to avoid excesses of any particular calorie source, provide nutrients and incorporate regular exercise. It isn't difficult to determine how to lose weight, the difficulty is in applying a particular choice. Regards David -- To email me, please include the letters DNF anywhere in the subject line. All other mail is automatically deleted. |
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Man... is this pulling out the swords and declaring war. And, the
declaration that we need a new army of professional diet therapists or their equivalent. And that what is needed is not LOW FAT but VERY LOW FAT diets, possibly administered by therapists..... This rings of Dr. Dean Ornish again springing into action to fill the void left by the negative $400 million study on the lack of benefit of LOW FAT. The alleged hidden secret of the first trials of the Ornish ultra-low fat diet in fact had intensive personal therapy for the participants in making this enormous change in eating style. The same study allegedly had intensive physical exercise programs which were also administered by the diet therapists. A few items extracted from the long paper below..... These diet people are as despicable as politicians .... Jim ------------------------------------------------------------- Should..... Suggest ..... may cause Professionally conducted weight-control programs are far more likely to help people lose weight than self-help approaches. (12) Perhaps the greatest irony in the current low-carb craze pertains to the overwhelming scientific evidence showing that self-help andother minimal interventions(for example, diet books and instructions alone)rarely help people lose much weight. Yet, publications in prestigious journals with favorable editorial commentaries, public relations campaigns, anecdotal claims, salesof millions ofbooks, and countless stories inthe media have prompted literally thousands of papers addressing this issue. (2,16) As would be expected from these results, highly successful adult weight-controllers consume much less fat than average Americans and about 10 times the level of carbohydrates recommended by Atkins. (25) Weight-loss programs that counsel people to eat like this have produced among the most promising outcomes in long-term evaluations. (26) Yet, the scientific evidence shows that more stringent goals for fat consumption seem easier (not harder) to implement consistently, make more sense physiologically, and produce the most promising results. Unless valid scientific research shows reliable and differential weight loss and other benefits for low-carb diets, which seems unlikely at this juncture, the recommended pathway to successful weight control should include a very-low-fat diet, not a low-carb/high-fat diet. Roger Zoul wrote: Very-low-fat diets are superior to low-carbohydrate diets: evidence shows that very-low-fat diets (not low- or moderate-fat diets) may be easier, not harder, to follow and make more sense physiologically. They should also produce the best weight loss and health outcomes They should also produce the best weight loss and health outcomes in the long run.(VIEWPOINT). Daniel S. Kirschenbaum. Patient Care 39.11 (Nov 2005): p47(7). For more than half a century, millions of Americans have periodically followed diets that were very low in carbohydrates (and high in protein and fat) in search of the best and easiest way to lose weight. The late Robert C. Atkins' 1998 revision of his 1972 Dr. Atkins' Diet Revolution was on the New York Times best-seller list for more than 6 years, and many other best-sellers have advocated similar low-carbohydrate diets. (1) Several professional organizations, including the American Dietetic Association (ADA) and the American Heart Association (AHA), have advised against the use of low-carb diets because considerable scientific evidence suggests that diets like these may promote cardiovascular, kidney, and liver diseases, as well as cancer. (2) evidence suggests that diets like these may promote cardiovascular, Despite the ostensible health risks of low-carb diets, some people have followed this approach and lost weight. Despite the ostensible health risks of low-carb diets, some people have followed this approach and lost weight. This anecdotal evidence, coupled with successful marketing campaigns, has led even neutral consumer advocates to encourage weight controllers to "add a little fat" to their diets. (3) Despite waning interest in this approach, acceptance of the supposed benefits of low-carb dieting still appears routinely in the media and is evident in restaurant menus and on supermarket shelves. Only a careful review of the scientific literature can determine whether health professionals should recommend or oppose low-carb dieting for their confused overweight patients. Bravata et al recently identified 2616 articles in professional journals (including 94 empirical studies) pertaining to the efficacy of low-carb dieting. (2) However, only 6 studies--5 of them published since the Bravata review was completed--have compared low-carb/moderate- to high-fat diets with diets described as "low-fat" using random assignment and evaluations lasting at least 6 months. (4-10) The authors of 4 of these 6 studies concluded that their low-carb diets helped their overweight participants lose more weight than their low-fat diets. (4,6,7-9) A critical review of these studies, however, reveals that none provides scientifically valid evidence for this claim. This article presents the basis for this assertion and provides an empirically grounded rationale for recommending very low-fat diets. Flaws in research designs Three major flaws in research designs undermine the validity of these studies. First, all 4 of the studies that found some ostensible benefits for low-carb diets used elaborate intervention programs (for example, 18 months of weekly sessions), not dietary instructions alone. (4,6,7-9) Including the diets within extensive programs confounds the integrity of the independent variable, decreasing internal validity ("diffusion of treatment") and external validity ("multiple treatment interference"). (11) Second, the administrators of these diet/behavioral programs had far more opportunities for their beliefs or biases to have an impact on outcomes than they would have had in a study, like that of Foster et al, that used a diet intervention alone. (5) This raises possibilities of investigator and experimenter bias that threaten both internal and external validity ("reactivity of experimental arrangements" and "combination of experimental setting and treatment"). (11) Two of the 4 studies that supported the supposed differential benefits of low-carbohydrate diets were funded by companies (olive oil and peanut companies and The Dr. Robert C. Atkins Foundation) that had--and still have--major financial allegiances to low-carbohydrate diets. (6,8) This fact clearly increases the salience of concerns about investigator/experimenter bias, although it by no means impugns the integrity of the researchers. The third design flaw is the most important: None of the 4 studies that ostensibly found benefits for low-carb diets used a truly low-fat diet (for example, 5%-10% of calories from fat), sometimes referred to as a very-low-fat diet. Thus, these studies actually compared low-carb diets with moderate-fat diets (goals were 20%, (6) 25%, (5) and 30% (4,7,8) of calories from fat; obtained: 29%-33%), thereby creating a "construct validity" problem. (11) When is a diet a diet? Only Foster et al tested the relative efficacy of a diet per se, as it is usually attempted by the millions of people who buy diet books. (5) This study also yielded no differences between low-carb and low-fat diets at a 1-year follow-up and produced about half the weight loss in their best group, as compared with the best group of 2 of the other studies. (4,8) The remaining studies tested dietary instructions within educational and behavioral programs. Professionally conducted weight-control programs are far more likely to help people lose weight than self-help approaches. (12) In fact, a meta-analysis showed that the single best predictor of weight loss is length of treatment. (13) Longer treatments also produced much more weight loss in studies that experimentally compared longer to shorter treatments. (14) These effects of amount of contact with professionals emerge almost regardless of the content that is focused on within the sessions. (15) Apparently, participation in such programs helps weight-controllers set goals, monitor and evaluate their behaviors, and generally stay motivated, optimistic, and focused on change. These findings indicate that the 5 low-carb studies under consideration here that embedded the diets within educational/behavioral programs must attribute some of their effects to the programs themselves, not the diets. Investigator and experimenter bias Investigators' hypotheses can intentionally or unintentionally affect the manner in which the experimental protocol is specified and delivered and the accuracy of data gathering and analyses. Similarly, experimenters (in these studies, dietitians) can affect recruitment and retention of participants. [GRAPHIC OMITTED] In the present set of studies, the researchers and dietitians probably knew that publication, notoriety, and subsequent funding may have depended on finding benefits for low-carb diets. The enthusiasm of the dietitians who administered the programs could have varied according to condition, quite possibly unintentionally, thereby affecting attrition and recruitment for evaluations. In fact, the attrition in some of the low-fat groups was as much as 400% higher than the usual attrition rate for related behavioral programs that used low-fat or very-low-fat diets (80% versus 20%) and was significantly higher in low-fat compared with low-carb groups in 3 of the 6 studies. (6,7,8,15) This suggests the possibility of differential enthusiasm for the treatments. Research on investigator and experiment bias has revealed some dramatic effects, including studies showing that experimenters' computational errors favor investigators' hypotheses 75% of the time. (16) The authors of the 2 studies under review here that received financial support from companies with vested interests in low-carbohydrate diets based their conclusions favoring low-carb/moderate-to-high fat diets on potentially flawed analyses. (6,8) First, the "primary analyses" of McManus et al were conducted using a "low-fat" group in which 67% (20 of 30) subjects analyzed had dropped out of the program. (6) Thus, they almost certainly were no longer following the low-fat approach when they were counted as "low-fat" dieters. This group was compared with a higher-fat group comprising 25 active participants and only 6 dropouts. Forty additional dropouts were not "available for measurements." Based purely on research showing the powerful impact of active participation in weight-loss programs, 67% of the low-fat group included in the primary analyses would be expected to fare poorly, compared with 19% of the low-carb group. (13) This differential subject attrition, one of the primary threats to internal validity, was statistically very significant (P .001) but ignored by the authors. When the researchers compared only current participants (excluding dropouts), the groups did not differ in weight loss. The quality and outcomes of the manipulation checks in the study by Yancy et al raise questions about the nature of the independent variable (the distinctiveness and characterizations of the diets). (8) The Atkins' (low-carb) diet group was instructed to consume less than 20 g/d of carbohydrates--a severely restricted level of carbohydrate consumption. The authors noted that carbohydrate consumption under 40 g/d (twice the allowed level) should have been readily detected by urinary dipstick tests. However, only 19 of 59 (32%) participants included in analyses had observed trace levels of ketones. Since the vast majority of those assigned to the low-carbohydrate diet failed to restrict their carbohydrate consumption enough to be detected at twice the allowed level, it seems problematic to consider this group to be a "low-carbohydrate diet group." Perhaps the researchers considered their dietary assignments to be successful based on analyses of the diets reportedly consumed by participants. Unfortunately, only 20 out of 119 (17%) of participants were selected (not randomly assigned: 13 low-carb dieters, 7 low-fat dieters) for analyses of their diets. No measure of the reliability of these dietary assessments was reported. Even if participants had followed Yancy et al's dietary manipulation exactly as intended, these researchers, like McManus et al, largely ignored the potential impact of differential subject attrition. (6,8) The Yancy study did not acknowledge the McManus study or others showing that dropouts often fail to lose weight, compared with those who stay in treatment. (13,15) The McManus and Yancy low-fat participants prematurely discontinued treatment almost twice as often (43%) as their low-carbohydrate groups (24%). Unlike McManus et al, however, Yancy et al did not analyze the data separately for completers only. Without taking into account the likely poorer performance of the greater number of dropouts in the low-fat group, Yancy et al may have inadvertently skewed the results in favor of their low-carbohydrate group. Furthermore, the use of linear mixed-effects models to project expected weight losses (instead of analyzing the data actually obtained) may have capitalized on the well-known effect of low-carbohydrate diets to produce initially greater weight losses. (9) Also, as Yancy et al noted, their use of projected values depended on the assumption that including dropouts would not affect the meaning of the results ("noninformative dropouts"). In weight-control research, however, dropouts lose less weight than completers. (13,15) Therefore, including these dropouts "informed" the outcomes, thereby perhaps violating an assumption of the analyses. This argument gains support by calculating the impact on the results of including the dropouts. The low-carbohydrate dieters were projected to lose 85% more weight than those assigned to the low-fat group at the 24-week point. When dropouts are deleted from these projections (counting them as losing no weight in both diet conditions), the discrepancy between groups decreases substantially. The projected difference decreases by 236% (from 85% to 36%), quite possibly rendering the actual differences between groups nonsignificant. When is a low-fat diet a low-fat diet? The biggest problem in the studies that supposedly favored low-carb diets was the failure to use truly low-fat diets. Samaha et al used a moderate-fat goal, 30% calories from fat, in their "low-fat" group. (7) They reported a baseline level of fat consumption by that group of 33% of calories from fat (68 g/d) and even after "six months of dietary counseling," this group averaged the same percentage of calories from fat (33%; 57.8 g fat). Data in McManus et al also showed minimal changes and moderate levels of fat consumption at baseline (31%) and follow-up (30%) in the low-fat group. (6) Brehm et al and Yancy et al used low-fat goals of about 30%, and they both reported 29% fat consumption during the program. (4,8) In their extensive review of the efficacy of popular diets, Freedman et al categorized the level of fat consumption obtained in these 4 studies as "moderate-fat." (16) Current evidence suggests that the moderately high levels of fat consumption achieved in these studies should not have helped weight-controllers succeed. (17,18) In a review of dietary interventions, Barnard et al reported that "only very stringent dietary manipulations led to effective change." (19) They found that the 3 studies that clearly produced the greatest changes in diets limited "dietary fat to no more than 10% of energy," not the 25% to 30% of calories from fat used by almost all of the other 27 studies in their review and obtained (29%-33%) by the studies under discussion here. Freedman et al also asserted that "data support the contention that those consuming low-fat, low-calorie diets are most successful in maintaining weight loss." (16) Stice's survey of 396 adolescents also illustrates the differential benefits of very-low-fat compared with low/moderate-fat diets. (20) He found that only those who followed a very stringent approach lost weight; those who reported following more moderate diets actually gained weight. Weight-controllers in Jeffery et al also found a low-fat approach easier to use and more palatable than a calorically restricted diet without limits on fat. (21) (It's easier to eat no potato chips at all than just one.) The data from both these studies and the Barnard et al review support Barnard's conclusion: "Higher limits on fat intake, which may be selected in hopes of maximizing the acceptability of prescribed diets, may actually discourage a greater degree of dietary change." (19) Lowering levels of fat consumption is crucial [GRAPHIC OMITTED] Other analyses of the impact of macronutrients on weight change support the view that moderate (and certainly high) fat consumption can inhibit weight loss and maintenance of reduced weight. The extensive review of the efficacy of low-carb diets in Bravata et al showed that "among obese patients, weight loss was associated with longer diet duration, restriction of caloric intake, but not with reduced carbohydrate content". (2) The Freedman et al review also found no support for the benefits of reducing carbohydrate content, without restricting calories, on weight loss. (16) For example, Harris et al studied 157 weight-controllers over 18 months and found that reducing the percentage of calories from carbohydrates (and protein) did not affect weight loss. (22) In contrast, eating very little fat, and specifically minimizing consumption of beef, hot dogs, and sweets, did predict weight loss (as it did in Holden et al). (23) Reducing calories from fat actually predicted weight loss even better than change in total calories (as it did in Jeffery et al). (21) In a remarkably similar vein, but with children as the focus, Gazzaniga and Burns found that a group of obese children ate much more fat and many fewer carbohydrates than their lean peers. (24) Even after statistically adjusting for total energy intake, physical activity, and metabolic rates, obese children still ate more fat and fewer carbohydrates. Animal and physiologic research also supports the benefits of truly low-fat diets compared with moderate-fat diets. Several studies showed that animals fed high-fat diets gained weight much more readily than those fed diets much lower in fat. (27) Boozer et al also found that high-fat diets not only promote weight gain but also inhibit weight loss. (28) They compared several groups of rats whose food was restricted to 75% of the calories in their baseline diets. The rats that were fed high-fat, restricted-calorie diets (45% fat) failed to lose weight, compared with rats that consumed diets of the same restricted calorie level that were moderately high in fat (28%) and low in fat (12%). Three human studies also found that much-lower-fat diets resulted in weight loss even when total calories were not reduced, an effect never obtained with low-carb diets. (16) Bessesen et al demonstrated a method through which high-fat diets inhibit weight loss. (29) They found that when obese rats consumed dietary fat, it was transported to storage in fat cells and away from muscle cells much more so than was the case in lean rats. This pattern was accentuated for formerly obese rats. Formerly overweight people also show a differential sensitivity to fat at the cellular level. (30) They may also have greater physiologic sensitivity (insulin secretion, salivation) to the presence and even the thought of highly palatable high-fat food. (31) Consuming high-fat foods may also encourage overeating by increasing appetite and decreasing satiety to a greater extent than low-fat foods. (32) This may occur because eating such foods may stimulate the endogenous opioid peptide system. Consuming a high-fat diet also induces heightened sensitivity to leptin, leads to increases in ghrelin, and inhibits the transportation of insulin into the brain, all of which probably increase eating and weight gain. (16) In fact, a recent study showed that a very low-fat/high-carbohydrate diet (15% calories from fat, 65% carbohydrate, 20% protein) failed to trigger the type of increase in ghrelin (a potent orexigenic signal) that is typically seen when people lose weight by restricting calories in higher-fat diets. (33) Why were truly low-fat diets not used in these studies? This evidence raises questions about why these researchers chose "low-fat" dietary levels (actually "moderate-fat" diets, according to Freedman et al) that were 50% to 100% higher than genuinely "low-fat" or "very-low-fat" levels. (16) Part of the answer is that the current evidence, while compelling, remains somewhat controversial and circumstantial. Definitive treatment outcome studies that clearly favor very-low-fat diets have not yet emerged, although the evidence certainly points in that direction. The reliance on tradition (actually, myths) provides another explanation. For decades, major professional groups that focus on diet and health (such as the AHA and ADA) have advocated moderation as the key to success in weight control. Extreme approaches, or so the myth goes, will not work because they induce feelings of deprivation and binge eating. Yet, the scientific evidence shows that more stringent goals for fat consumption seem easier (not harder) to implement consistently, make more sense physiologically, and produce the most promising results. Implications Perhaps the greatest irony in the current low-carb craze pertains to the overwhelming scientific evidence showing that self-help and other minimal interventions (for example, diet books and instructions alone) rarely help people lose much weight. Yet, publications in prestigious journals with favorable editorial commentaries, public relations campaigns, anecdotal claims, sales of millions of books, and countless stories in the media have prompted literally thousands of papers addressing this issue. (2,16) It is time for diet to be put in its place. A diet is just one element that can facilitate weight loss only when weight-controllers sustain major efforts to transform their lifestyles (activity level, stress management, focusing, and commitment). Furthermore, even when extracting the contribution of diet on weight loss, the possible long-term risks of low-carbohydrate/high-fat diets and some noteworthy short-term adverse effects (such as significantly increased GI distress, headaches, and muscle weakness) should discourage the use of such diets. (8) Unless valid scientific research shows reliable and differential weight loss and other benefits for low-carb diets, which seems unlikely at this juncture, the recommended pathway to successful weight control should include a very-low-fat diet, not a low-carb/high-fat diet. This article was contributed by Dr Kirschenbaum and edited by Peter D'Epiro, PhD. Dr Kirschenbaum discloses that he is Clinical Director and Chief Program Officer, Healthy Living Academies Division of Aspen Education Group, Cerritos, Calif. www.patientcareonline.com Visit our Web site for * Quick access to the reports and Internet resources discussed in these pages REFERENCES 1. Atkins RC. Dr. Atkins' New Diet Revolution (Revised and Updated). New York, NY: Avon Books; 1998. 2. Bravata DM, Sanders L, Huang J, et al. Efficacy and safety of low-carbohydrate diets: a systematic review. JAMA. 2003;289:1837-1850. 3. The truth about dieting. Consumer Reports. 2002;67:26-31. 4. Brehm BJ, Seeley RJ, Daniels SR, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrin Metab. 2003;88:1617-1623. 5. Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-carbohydrate diet for obesity. New Engl J Med. 2003;348:2082-2090. 6. McManus K, Antinoro L, Sacks F. A randomized controlled trial of a moderate-fat, low-energy diet compared with a low fat, low-energy diet for weight loss in overweight adults. Int J Obesity. 2001;25:1503-1511. 7. Samaha FF, Iqbal N, Seshadri P, et al. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 2003;348:2074-2081. 8. Yancy WS, Olsen MK, Guyton JR, et al. A low-carbohydrate ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia. Ann Intern Med. 2004;140:769-777. 9. Stern L, Iqbal N, Seshadri P, et al. The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial. Ann Intern Med. 2004;140:778-785. 10. Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005;293:43-53. 11. Cook TD, Campbell DT. Quasi-Experimentation: Design and Analysis Issues for Field Settings. Chicago, III: Rand McNally College Publishing Company; 1979. 12. Heshka S, Greenway F, Anderson JW, et al. Self-help weight loss versus a structured commercial program after twenty-six weeks: a randomized controlled study. Am J Med. 2000;109:282-287. 13. Bennett GA. Behavior therapy for obesity: a quantitative review of selected treatment characteristics on outcome. Behav Ther. 1986;17:554-562. 14. Baum JG, Clark HB, Sandler J. Preventing relapse in obesity through post treatment maintenance systems: comparing the relative efficacy of two levels of therapist support. J Behav Med. 1991;14:287-302. 15. Kaplan RM, Atkins CJ. Selective attrition causes over estimates of treatment effects in studies of weight loss. Add Behav. 1987;12:297-302. 16. Freedman MR, King J, Kennedy E. Popular diets: a scientific review. Obes Res. 2001(suppl 1):1S-40S. 17. Perri MG, Nezu AM, Viegener BJ. Improving the Long-Term Management of Obesity: Theory, Research, and Clinical Guidelines. New York, NY: John Wiley & Sons; 1992. 18. Barber TX. Pitfalls in Human Research: Ten Pivotal Points. New York, NY: Pergamon Press; 1976. 19. Barnard ND, Akhtar A, Nicholson A. Factors that facilitate compliance to lower fat intake. Arch Fam Med. 1995;4:153-158. 20. Stice E. Prospective relation of dieting behaviors to weight change in a community sample of adolescents. Behav Ther. 1998;29:277-297. 21. Jeffery RW, Hellerstedt WL, French SA, et al. A randomized trial of counseling for fat restriction versus calorie restriction in the treatment of obesity. Int J Obesity. 1995;19:132-137. 22. Harris JK, French SA, Jeffery RW, et al. Dietary and physical activity correlates of long-term weight loss. Obes Res. 1994;2:307-313. 23. Holden JH, Darga LL, Olson SM, et al. Long-term follow-up of patients attending a combination very-low calorie diet and behaviour therapy weight loss programme. Int J Obes. 1991;16:605-613. 24. Gazzaniga JM, Burns TL. Relationship between diet composition and body fatness, with adjustment for resting energy expenditure and physical activity, in preadolescent children. Am J Clin Nutr. 1993;58:21-28. 25. Shick SM, Wing RR, Klem ML, et al. Persons successful at long-term weight loss and maintenance continue to consume a low-energy, low-fat diet. J Amer Diet Assoc. 1998;98:408-413. 26. Wadden TA, Foster GD, Letizia KA, et al. A multicenter evaluation of a proprietary weight reduction program for the treatment of marked obesity. Arch Intern Med. 1992;152:961-966. 27. Salmon DMW, Flatt JP. Effect of dietary fat content on the incidence of obesity among ad libitum fed mice. Int J Obes. 1985;9:443-9. 28. Boozer CN, Brasseur A, Atkinson RL. Dietary fat affects weight loss and adiposity during energy restriction in rats. Am J Clin Nutr. 1993;58:846-852. 29. Bessesen DH, Rupp CL, Eckel RH. Dietary fat is shunted away from oxidation, toward storage in obese Zucker rats, Obes Res. 1995;3:179-189. 30. Tremblay A, Despres JP, Bouchard C. Adipose tissue characteristics of ex-obese long-distance runners. Int J Obes. 1984;8:641-648. 31. Johnson WG, Wildman HE. Influence of external and covert food stimuli on insulin secretion in obese and normal persons. Behav Neurol. 1983;97:1025-1028. 32. Blundell JE, Cotton JR, Delargy H, et al. The fat paradox: fat-induced satiety signals versus high fat overconsumption. Int J Obes. 1995;19:832-835. 33. Weigle DS, Cummings DE, Newby PD, et al. Roles of leptin and ghrelin in the loss of body weight caused by a low fat, high carbohydrate diet. J Clin Endocrinol Metab. 2003;88:1577-1586. DANIEL S. KIRSCHENBAUM, PhD Clinical Director and Chief Program Officer, Healthy Living Academies Division of Aspen Education Group, Cerritos, Calif; Director, Center for Behavioral Medicine & Sport Psychology; and Professor of Psychiatry and Behavioral Sciences, Northwestern University Medical School, Chicago, Ill. His most recent book is The Healthy Obsession Program: Smart Weight Loss Instead of Low-Carb Lunacy (http://www.benbellabooks.com). RELATED ARTICLE: Article at a glance ** Five studies published in the past 3 years compared low-carbohydrate to low-fat diets using random assignment and evaluations lasting about 6 months or longer. ** The authors of most of these studies concluded that their low-carb diets helped their overweight participants lose more weight than their low-fat diets. ** A critical review, however, reveals that none of these studies provides valid evidence of the differential effectiveness for weight control favoring low-carb diets. ** This analysis provides an empirically grounded rationale for recommending truly low-fat diets for weight loss, unless and until valid evidence suggests otherwise. Low-carb Sample Menu Breakfast Cheese-baked eggs Sausage patties Tea or decaf coffee with cream and sugar substitute Lunch Chicken croquettes on a bed of lettuce Sugar-free orange gelatin parfait Dinner Sour cream clam dip with fried pork rinds Fennel red snapper Tossed green salad with creamy dijon vinaigrette dressing Tea or decaf coffee with cream and sugar substitute Snack Vanilla ice cream Low-fat Sample Menu Breakfast Egg white omelet with red potatoes, fat-free cheese, diced onion, and garlic Nonfat blended berry yogurt Berries Herbal tea or coffee with skim milk and sugar substitute Lunch Pepperoni pita pocket pizza (fat-free pita bread, pizza sauce, soy pepperoni, fat-free shredded jack and cheddar cheese) Low-fat split pea or vegetable soup Iced tea or diet soda Dinner Broiled lobster with lemon Roasted new potatoes Asparagus Salad with fat-free dressing Fruit salad and frozen sorbet or yogurt Hot herbal tea or diet soda Snack Pretzels, low-fat popcorn, or whole fruit -- 1) Eat Till SATISFIED, Not STUFFED... Atkins repeated 9 times in the book 2) Exercise: It's Non-Negotiable..... Chapter 22 title, Atkins book 3) Don't Diet Without Supplemental Nutrients... Chapter 23 title, Atkins book 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) |
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Jbuch wrote: Man... is this pulling out the swords and declaring war. And, the declaration that we need a new army of professional diet therapists or their equivalent. And that what is needed is not LOW FAT but VERY LOW FAT diets, possibly administered by therapists..... This rings of Dr. Dean Ornish again springing into action to fill the void left by the negative $400 million study on the lack of benefit of LOW FAT. That's what I thought too. The inescapable conclusion from the recent NUH study results are that in the real world trying to do low fat doesn't work. The women doing low fat did achieve a significant reduction in fat intake for 8 years, with no statistical reduction in CHD or cancer. They met with nutritionists at least 4 times a year and many times more than that in the first couple years. They volunteered for the study and were motivated at least as much as the average person trying to follow low fat, and likely much more. So, rather than accept that what these alleged experts have been telling us for years is wrong, and it's time for a re-evaluation and a long term study of something else like low carb, the spin misters are out with this sorry sack of crap, It's not that they are all wrong. It's that the women who tried their best to do low fat simply failed and the reason no benefit was found was that they had to go to very low fat. How exactly are they proposing for 48000 women to do that for 8 years? Lock them up in a lab? And how the hell is the general population going to do this? Do these idiots even have a clue? The alleged hidden secret of the first trials of the Ornish ultra-low fat diet in fact had intensive personal therapy for the participants in making this enormous change in eating style. The same study allegedly had intensive physical exercise programs which were also administered by the diet therapists. A few items extracted from the long paper below..... These diet people are as despicable as politicians .... Jim ------------------------------------------------------------- Should..... Suggest ..... may cause Professionally conducted weight-control programs are far more likely to help people lose weight than self-help approaches. (12) Perhaps the greatest irony in the current low-carb craze pertains to the overwhelming scientific evidence showing that self-help andother minimal interventions(for example, diet books and instructions alone)rarely help people lose much weight. Yet, publications in prestigious journals with favorable editorial commentaries, public relations campaigns, anecdotal claims, salesof millions ofbooks, and countless stories inthe media have prompted literally thousands of papers addressing this issue. (2,16) As would be expected from these results, highly successful adult weight-controllers consume much less fat than average Americans and about 10 times the level of carbohydrates recommended by Atkins. (25) Weight-loss programs that counsel people to eat like this have produced among the most promising outcomes in long-term evaluations. (26) Yet, the scientific evidence shows that more stringent goals for fat consumption seem easier (not harder) to implement consistently, make more sense physiologically, and produce the most promising results. Unless valid scientific research shows reliable and differential weight loss and other benefits for low-carb diets, which seems unlikely at this juncture, the recommended pathway to successful weight control should include a very-low-fat diet, not a low-carb/high-fat diet. Roger Zoul wrote: Very-low-fat diets are superior to low-carbohydrate diets: evidence shows that very-low-fat diets (not low- or moderate-fat diets) may be easier, not harder, to follow and make more sense physiologically. They should also produce the best weight loss and health outcomes They should also produce the best weight loss and health outcomes in the long run.(VIEWPOINT). Daniel S. Kirschenbaum. Patient Care 39.11 (Nov 2005): p47(7). For more than half a century, millions of Americans have periodically followed diets that were very low in carbohydrates (and high in protein and fat) in search of the best and easiest way to lose weight. The late Robert C. Atkins' 1998 revision of his 1972 Dr. Atkins' Diet Revolution was on the New York Times best-seller list for more than 6 years, and many other best-sellers have advocated similar low-carbohydrate diets. (1) Several professional organizations, including the American Dietetic Association (ADA) and the American Heart Association (AHA), have advised against the use of low-carb diets because considerable scientific evidence suggests that diets like these may promote cardiovascular, kidney, and liver diseases, as well as cancer. (2) evidence suggests that diets like these may promote cardiovascular, Despite the ostensible health risks of low-carb diets, some people have followed this approach and lost weight. Despite the ostensible health risks of low-carb diets, some people have followed this approach and lost weight. This anecdotal evidence, coupled with successful marketing campaigns, has led even neutral consumer advocates to encourage weight controllers to "add a little fat" to their diets. (3) Despite waning interest in this approach, acceptance of the supposed benefits of low-carb dieting still appears routinely in the media and is evident in restaurant menus and on supermarket shelves. Only a careful review of the scientific literature can determine whether health professionals should recommend or oppose low-carb dieting for their confused overweight patients. Bravata et al recently identified 2616 articles in professional journals (including 94 empirical studies) pertaining to the efficacy of low-carb dieting. (2) However, only 6 studies--5 of them published since the Bravata review was completed--have compared low-carb/moderate- to high-fat diets with diets described as "low-fat" using random assignment and evaluations lasting at least 6 months. (4-10) The authors of 4 of these 6 studies concluded that their low-carb diets helped their overweight participants lose more weight than their low-fat diets. (4,6,7-9) A critical review of these studies, however, reveals that none provides scientifically valid evidence for this claim. This article presents the basis for this assertion and provides an empirically grounded rationale for recommending very low-fat diets. Flaws in research designs Three major flaws in research designs undermine the validity of these studies. First, all 4 of the studies that found some ostensible benefits for low-carb diets used elaborate intervention programs (for example, 18 months of weekly sessions), not dietary instructions alone. (4,6,7-9) Including the diets within extensive programs confounds the integrity of the independent variable, decreasing internal validity ("diffusion of treatment") and external validity ("multiple treatment interference"). (11) Second, the administrators of these diet/behavioral programs had far more opportunities for their beliefs or biases to have an impact on outcomes than they would have had in a study, like that of Foster et al, that used a diet intervention alone. (5) This raises possibilities of investigator and experimenter bias that threaten both internal and external validity ("reactivity of experimental arrangements" and "combination of experimental setting and treatment"). (11) Two of the 4 studies that supported the supposed differential benefits of low-carbohydrate diets were funded by companies (olive oil and peanut companies and The Dr. Robert C. Atkins Foundation) that had--and still have--major financial allegiances to low-carbohydrate diets. (6,8) This fact clearly increases the salience of concerns about investigator/experimenter bias, although it by no means impugns the integrity of the researchers. The third design flaw is the most important: None of the 4 studies that ostensibly found benefits for low-carb diets used a truly low-fat diet (for example, 5%-10% of calories from fat), sometimes referred to as a very-low-fat diet. Thus, these studies actually compared low-carb diets with moderate-fat diets (goals were 20%, (6) 25%, (5) and 30% (4,7,8) of calories from fat; obtained: 29%-33%), thereby creating a "construct validity" problem. (11) When is a diet a diet? Only Foster et al tested the relative efficacy of a diet per se, as it is usually attempted by the millions of people who buy diet books. (5) This study also yielded no differences between low-carb and low-fat diets at a 1-year follow-up and produced about half the weight loss in their best group, as compared with the best group of 2 of the other studies. (4,8) The remaining studies tested dietary instructions within educational and behavioral programs. Professionally conducted weight-control programs are far more likely to help people lose weight than self-help approaches. (12) In fact, a meta-analysis showed that the single best predictor of weight loss is length of treatment. (13) Longer treatments also produced much more weight loss in studies that experimentally compared longer to shorter treatments. (14) These effects of amount of contact with professionals emerge almost regardless of the content that is focused on within the sessions. (15) Apparently, participation in such programs helps weight-controllers set goals, monitor and evaluate their behaviors, and generally stay motivated, optimistic, and focused on change. These findings indicate that the 5 low-carb studies under consideration here that embedded the diets within educational/behavioral programs must attribute some of their effects to the programs themselves, not the diets. Investigator and experimenter bias Investigators' hypotheses can intentionally or unintentionally affect the manner in which the experimental protocol is specified and delivered and the accuracy of data gathering and analyses. Similarly, experimenters (in these studies, dietitians) can affect recruitment and retention of participants. [GRAPHIC OMITTED] In the present set of studies, the researchers and dietitians probably knew that publication, notoriety, and subsequent funding may have depended on finding benefits for low-carb diets. The enthusiasm of the dietitians who administered the programs could have varied according to condition, quite possibly unintentionally, thereby affecting attrition and recruitment for evaluations. In fact, the attrition in some of the low-fat groups was as much as 400% higher than the usual attrition rate for related behavioral programs that used low-fat or very-low-fat diets (80% versus 20%) and was significantly higher in low-fat compared with low-carb groups in 3 of the 6 studies. (6,7,8,15) This suggests the possibility of differential enthusiasm for the treatments. Research on investigator and experiment bias has revealed some dramatic effects, including studies showing that experimenters' computational errors favor investigators' hypotheses 75% of the time. (16) The authors of the 2 studies under review here that received financial support from companies with vested interests in low-carbohydrate diets based their conclusions favoring low-carb/moderate-to-high fat diets on potentially flawed analyses. (6,8) First, the "primary analyses" of McManus et al were conducted using a "low-fat" group in which 67% (20 of 30) subjects analyzed had dropped out of the program. (6) Thus, they almost certainly were no longer following the low-fat approach when they were counted as "low-fat" dieters. This group was compared with a higher-fat group comprising 25 active participants and only 6 dropouts. Forty additional dropouts were not "available for measurements." Based purely on research showing the powerful impact of active participation in weight-loss programs, 67% of the low-fat group included in the primary analyses would be expected to fare poorly, compared with 19% of the low-carb group. (13) This differential subject attrition, one of the primary threats to internal validity, was statistically very significant (P .001) but ignored by the authors. When the researchers compared only current participants (excluding dropouts), the groups did not differ in weight loss. The quality and outcomes of the manipulation checks in the study by Yancy et al raise questions about the nature of the independent variable (the distinctiveness and characterizations of the diets). (8) The Atkins' (low-carb) diet group was instructed to consume less than 20 g/d of carbohydrates--a severely restricted level of carbohydrate consumption. The authors noted that carbohydrate consumption under 40 g/d (twice the allowed level) should have been readily detected by urinary dipstick tests. However, only 19 of 59 (32%) participants included in analyses had observed trace levels of ketones. Since the vast majority of those assigned to the low-carbohydrate diet failed to restrict their carbohydrate consumption enough to be detected at twice the allowed level, it seems problematic to consider this group to be a "low-carbohydrate diet group." Perhaps the researchers considered their dietary assignments to be successful based on analyses of the diets reportedly consumed by participants. Unfortunately, only 20 out of 119 (17%) of participants were selected (not randomly assigned: 13 low-carb dieters, 7 low-fat dieters) for analyses of their diets. No measure of the reliability of these dietary assessments was reported. Even if participants had followed Yancy et al's dietary manipulation exactly as intended, these researchers, like McManus et al, largely ignored the potential impact of differential subject attrition. (6,8) The Yancy study did not acknowledge the McManus study or others showing that dropouts often fail to lose weight, compared with those who stay in treatment. (13,15) The McManus and Yancy low-fat participants prematurely discontinued treatment almost twice as often (43%) as their low-carbohydrate groups (24%). Unlike McManus et al, however, Yancy et al did not analyze the data separately for completers only. Without taking into account the likely poorer performance of the greater number of dropouts in the low-fat group, Yancy et al may have inadvertently skewed the results in favor of their low-carbohydrate group. Furthermore, the use of linear mixed-effects models to project expected weight losses (instead of analyzing the data actually obtained) may have capitalized on the well-known effect of low-carbohydrate diets to produce initially greater weight losses. (9) Also, as Yancy et al noted, their use of projected values depended on the assumption that including dropouts would not affect the meaning of the results ("noninformative dropouts"). In weight-control research, however, dropouts lose less weight than completers. (13,15) Therefore, including these dropouts "informed" the outcomes, thereby perhaps violating an assumption of the analyses. This argument gains support by calculating the impact on the results of including the dropouts. The low-carbohydrate dieters were projected to lose 85% more weight than those assigned to the low-fat group at the 24-week point. When dropouts are deleted from these projections (counting them as losing no weight in both diet conditions), the discrepancy between groups decreases substantially. The projected difference decreases by 236% (from 85% to 36%), quite possibly rendering the actual differences between groups nonsignificant. When is a low-fat diet a low-fat diet? The biggest problem in the studies that supposedly favored low-carb diets was the failure to use truly low-fat diets. Samaha et al used a moderate-fat goal, 30% calories from fat, in their "low-fat" group. (7) They reported a baseline level of fat consumption by that group of 33% of calories from fat (68 g/d) and even after "six months of dietary counseling," this group averaged the same percentage of calories from fat (33%; 57.8 g fat). Data in McManus et al also showed minimal changes and moderate levels of fat consumption at baseline (31%) and follow-up (30%) in the low-fat group. (6) Brehm et al and Yancy et al used low-fat goals of about 30%, and they both reported 29% fat consumption during the program. (4,8) In their extensive review of the efficacy of popular diets, Freedman et al categorized the level of fat consumption obtained in these 4 studies as "moderate-fat." (16) Current evidence suggests that the moderately high levels of fat consumption achieved in these studies should not have helped weight-controllers succeed. (17,18) In a review of dietary interventions, Barnard et al reported that "only very stringent dietary manipulations led to effective change." (19) They found that the 3 studies that clearly produced the greatest changes in diets limited "dietary fat to no more than 10% of energy," not the 25% to 30% of calories from fat used by almost all of the other 27 studies in their review and obtained (29%-33%) by the studies under discussion here. Freedman et al also asserted that "data support the contention that those consuming low-fat, low-calorie diets are most successful in maintaining weight loss." (16) Stice's survey of 396 adolescents also illustrates the differential benefits of very-low-fat compared with low/moderate-fat diets. (20) He found that only those who followed a very stringent approach lost weight; those who reported following more moderate diets actually gained weight. Weight-controllers in Jeffery et al also found a low-fat approach easier to use and more palatable than a calorically restricted diet without limits on fat. (21) (It's easier to eat no potato chips at all than just one.) The data from both these studies and the Barnard et al review support Barnard's conclusion: "Higher limits on fat intake, which may be selected in hopes of maximizing the acceptability of prescribed diets, may actually discourage a greater degree of dietary change." (19) Lowering levels of fat consumption is crucial [GRAPHIC OMITTED] Other analyses of the impact of macronutrients on weight change support the view that moderate (and certainly high) fat consumption can inhibit weight loss and maintenance of reduced weight. The extensive review of the efficacy of low-carb diets in Bravata et al showed that "among obese patients, weight loss was associated with longer diet duration, restriction of caloric intake, but not with reduced carbohydrate content". (2) The Freedman et al review also found no support for the benefits of reducing carbohydrate content, without restricting calories, on weight loss. (16) For example, Harris et al studied 157 weight-controllers over 18 months and found that reducing the percentage of calories from carbohydrates (and protein) did not affect weight loss. (22) In contrast, eating very little fat, and specifically minimizing consumption of beef, hot dogs, and sweets, did predict weight loss (as it did in Holden et al). (23) Reducing calories from fat actually predicted weight loss even better than change in total calories (as it did in Jeffery et al). (21) In a remarkably similar vein, but with children as the focus, Gazzaniga and Burns found that a group of obese children ate much more fat and many fewer carbohydrates than their lean peers. (24) Even after statistically adjusting for total energy intake, physical activity, and metabolic rates, obese children still ate more fat and fewer carbohydrates. Animal and physiologic research also supports the benefits of truly low-fat diets compared with moderate-fat diets. Several studies showed that animals fed high-fat diets gained weight much more readily than those fed diets much lower in fat. (27) Boozer et al also found that high-fat diets not only promote weight gain but also inhibit weight loss. (28) They compared several groups of rats whose food was restricted to 75% of the calories in their baseline diets. The rats that were fed high-fat, restricted-calorie diets (45% fat) failed to lose weight, compared with rats that consumed diets of the same restricted calorie level that were moderately high in fat (28%) and low in fat (12%). Three human studies also found that much-lower-fat diets resulted in weight loss even when total calories were not reduced, an effect never obtained with low-carb diets. (16) Bessesen et al demonstrated a method through which high-fat diets inhibit weight loss. (29) They found that when obese rats consumed dietary fat, it was transported to storage in fat cells and away from muscle cells much more so than was the case in lean rats. This pattern was accentuated for formerly obese rats. Formerly overweight people also show a differential sensitivity to fat at the cellular level. (30) They may also have greater physiologic sensitivity (insulin secretion, salivation) to the presence and even the thought of highly palatable high-fat food. (31) Consuming high-fat foods may also encourage overeating by increasing appetite and decreasing satiety to a greater extent than low-fat foods. (32) This may occur because eating such foods may stimulate the endogenous opioid peptide system. Consuming a high-fat diet also induces heightened sensitivity to leptin, leads to increases in ghrelin, and inhibits the transportation of insulin into the brain, all of which probably increase eating and weight gain. (16) In fact, a recent study showed that a very low-fat/high-carbohydrate diet (15% calories from fat, 65% carbohydrate, 20% protein) failed to trigger the type of increase in ghrelin (a potent orexigenic signal) that is typically seen when people lose weight by restricting calories in higher-fat diets. (33) Why were truly low-fat diets not used in these studies? This evidence raises questions about why these researchers chose "low-fat" dietary levels (actually "moderate-fat" diets, according to Freedman et al) that were 50% to 100% higher than genuinely "low-fat" or "very-low-fat" levels. (16) Part of the answer is that the current evidence, while compelling, remains somewhat controversial and circumstantial. Definitive treatment outcome studies that clearly favor very-low-fat diets have not yet emerged, although the evidence certainly points in that direction. The reliance on tradition (actually, myths) provides another explanation. For decades, major professional groups that focus on diet and health (such as the AHA and ADA) have advocated moderation as the key to success in weight control. Extreme approaches, or so the myth goes, will not work because they induce feelings of deprivation and binge eating. Yet, the scientific evidence shows that more stringent goals for fat consumption seem easier (not harder) to implement consistently, make more sense physiologically, and produce the most promising results. Implications Perhaps the greatest irony in the current low-carb craze pertains to the overwhelming scientific evidence showing that self-help and other minimal interventions (for example, diet books and instructions alone) rarely help people lose much weight. Yet, publications in prestigious journals with favorable editorial commentaries, public relations campaigns, anecdotal claims, sales of millions of books, and countless stories in the media have prompted literally thousands of papers addressing this issue. (2,16) It is time for diet to be put in its place. A diet is just one element that can facilitate weight loss only when weight-controllers sustain major efforts to transform their lifestyles (activity level, stress management, focusing, and commitment). Furthermore, even when extracting the contribution of diet on weight loss, the possible long-term risks of low-carbohydrate/high-fat diets and some noteworthy short-term adverse effects (such as significantly increased GI distress, headaches, and muscle weakness) should discourage the use of such diets. (8) Unless valid scientific research shows reliable and differential weight loss and other benefits for low-carb diets, which seems unlikely at this juncture, the recommended pathway to successful weight control should include a very-low-fat diet, not a low-carb/high-fat diet. This article was contributed by Dr Kirschenbaum and edited by Peter D'Epiro, PhD. Dr Kirschenbaum discloses that he is Clinical Director and Chief Program Officer, Healthy Living Academies Division of Aspen Education Group, Cerritos, Calif. www.patientcareonline.com Visit our Web site for * Quick access to the reports and Internet resources discussed in these pages REFERENCES 1. Atkins RC. Dr. Atkins' New Diet Revolution (Revised and Updated). New York, NY: Avon Books; 1998. 2. Bravata DM, Sanders L, Huang J, et al. Efficacy and safety of low-carbohydrate diets: a systematic review. JAMA. 2003;289:1837-1850. 3. The truth about dieting. Consumer Reports. 2002;67:26-31. 4. Brehm BJ, Seeley RJ, Daniels SR, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrin Metab. 2003;88:1617-1623. 5. Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-carbohydrate diet for obesity. New Engl J Med. 2003;348:2082-2090. 6. McManus K, Antinoro L, Sacks F. A randomized controlled trial of a moderate-fat, low-energy diet compared with a low fat, low-energy diet for weight loss in overweight adults. Int J Obesity. 2001;25:1503-1511. 7. Samaha FF, Iqbal N, Seshadri P, et al. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 2003;348:2074-2081. 8. Yancy WS, Olsen MK, Guyton JR, et al. A low-carbohydrate ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia. Ann Intern Med. 2004;140:769-777. 9. Stern L, Iqbal N, Seshadri P, et al. The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial. Ann Intern Med. 2004;140:778-785. 10. Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005;293:43-53. 11. Cook TD, Campbell DT. Quasi-Experimentation: Design and Analysis Issues for Field Settings. Chicago, III: Rand McNally College Publishing Company; 1979. 12. Heshka S, Greenway F, Anderson JW, et al. Self-help weight loss versus a structured commercial program after twenty-six weeks: a randomized controlled study. Am J Med. 2000;109:282-287. 13. Bennett GA. Behavior therapy for obesity: a quantitative review of selected treatment characteristics on outcome. Behav Ther. 1986;17:554-562. 14. Baum JG, Clark HB, Sandler J. Preventing relapse in obesity through post treatment maintenance systems: comparing the relative efficacy of two levels of therapist support. J Behav Med. 1991;14:287-302. 15. Kaplan RM, Atkins CJ. Selective attrition causes over estimates of treatment effects in studies of weight loss. Add Behav. 1987;12:297-302. 16. Freedman MR, King J, Kennedy E. Popular diets: a scientific review. Obes Res. 2001(suppl 1):1S-40S. 17. Perri MG, Nezu AM, Viegener BJ. Improving the Long-Term Management of Obesity: Theory, Research, and Clinical Guidelines. New York, NY: John Wiley & Sons; 1992. 18. Barber TX. Pitfalls in Human Research: Ten Pivotal Points. New York, NY: Pergamon Press; 1976. 19. Barnard ND, Akhtar A, Nicholson A. Factors that facilitate compliance to lower fat intake. Arch Fam Med. 1995;4:153-158. 20. Stice E. Prospective relation of dieting behaviors to weight change in a community sample of adolescents. Behav Ther. 1998;29:277-297. 21. Jeffery RW, Hellerstedt WL, French SA, et al. A randomized trial of counseling for fat restriction versus calorie restriction in the treatment of obesity. Int J Obesity. 1995;19:132-137. 22. Harris JK, French SA, Jeffery RW, et al. Dietary and physical activity correlates of long-term weight loss. Obes Res. 1994;2:307-313. 23. Holden JH, Darga LL, Olson SM, et al. Long-term follow-up of patients attending a combination very-low calorie diet and behaviour therapy weight loss programme. Int J Obes. 1991;16:605-613. 24. Gazzaniga JM, Burns TL. Relationship between diet composition and body fatness, with adjustment for resting energy expenditure and physical activity, in preadolescent children. Am J Clin Nutr. 1993;58:21-28. 25. Shick SM, Wing RR, Klem ML, et al. Persons successful at long-term weight loss and maintenance continue to consume a low-energy, low-fat diet. J Amer Diet Assoc. 1998;98:408-413. 26. Wadden TA, Foster GD, Letizia KA, et al. A multicenter evaluation of a proprietary weight reduction program for the treatment of marked obesity. Arch Intern Med. 1992;152:961-966. 27. Salmon DMW, Flatt JP. Effect of dietary fat content on the incidence of obesity among ad libitum fed mice. Int J Obes. 1985;9:443-9. 28. Boozer CN, Brasseur A, Atkinson RL. Dietary fat affects weight loss and adiposity during energy restriction in rats. Am J Clin Nutr. 1993;58:846-852. 29. Bessesen DH, Rupp CL, Eckel RH. Dietary fat is shunted away from oxidation, toward storage in obese Zucker rats, Obes Res. 1995;3:179-189. 30. Tremblay A, Despres JP, Bouchard C. Adipose tissue characteristics of ex-obese long-distance runners. Int J Obes. 1984;8:641-648. 31. Johnson WG, Wildman HE. Influence of external and covert food stimuli on insulin secretion in obese and normal persons. Behav Neurol. 1983;97:1025-1028. 32. Blundell JE, Cotton JR, Delargy H, et al. The fat paradox: fat-induced satiety signals versus high fat overconsumption. Int J Obes. 1995;19:832-835. 33. Weigle DS, Cummings DE, Newby PD, et al. Roles of leptin and ghrelin in the loss of body weight caused by a low fat, high carbohydrate diet. J Clin Endocrinol Metab. 2003;88:1577-1586. DANIEL S. KIRSCHENBAUM, PhD Clinical Director and Chief Program Officer, Healthy Living Academies Division of Aspen Education Group, Cerritos, Calif; Director, Center for Behavioral Medicine & Sport Psychology; and Professor of Psychiatry and Behavioral Sciences, Northwestern University Medical School, Chicago, Ill. His most recent book is The Healthy Obsession Program: Smart Weight Loss Instead of Low-Carb Lunacy (http://www.benbellabooks.com). RELATED ARTICLE: Article at a glance ** Five studies published in the past 3 years compared low-carbohydrate to low-fat diets using random assignment and evaluations lasting about 6 months or longer. ** The authors of most of these studies concluded that their low-carb diets helped their overweight participants lose more weight than their low-fat diets. ** A critical review, however, reveals that none of these studies provides valid evidence of the differential effectiveness for weight control favoring low-carb diets. ** This analysis provides an empirically grounded rationale for recommending truly low-fat diets for weight loss, unless and until valid evidence suggests otherwise. Low-carb Sample Menu Breakfast Cheese-baked eggs Sausage patties Tea or decaf coffee with cream and sugar substitute Lunch Chicken croquettes on a bed of lettuce Sugar-free orange gelatin parfait Dinner Sour cream clam dip with fried pork rinds Fennel red snapper Tossed green salad with creamy dijon vinaigrette dressing Tea or decaf coffee with cream and sugar substitute Snack Vanilla ice cream Low-fat Sample Menu Breakfast Egg white omelet with red potatoes, fat-free cheese, diced onion, and garlic Nonfat blended berry yogurt Berries Herbal tea or coffee with skim milk and sugar substitute Lunch Pepperoni pita pocket pizza (fat-free pita bread, pizza sauce, soy pepperoni, fat-free shredded jack and cheddar cheese) Low-fat split pea or vegetable soup Iced tea or diet soda Dinner Broiled lobster with lemon Roasted new potatoes Asparagus Salad with fat-free dressing Fruit salad and frozen sorbet or yogurt Hot herbal tea or diet soda Snack Pretzels, low-fat popcorn, or whole fruit -- 1) Eat Till SATISFIED, Not STUFFED... Atkins repeated 9 times in the book 2) Exercise: It's Non-Negotiable..... Chapter 22 title, Atkins book 3) Don't Diet Without Supplemental Nutrients... Chapter 23 title, Atkins book 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) |
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Roger Zoul wrote: First, the "primary analyses" of McManus et al were conducted using a "low-fat" group in which 67% (20 of 30) subjects analyzed had dropped out of the program. (6) Thus, they almost certainly were no longer following the low-fat approach when they were counted as "low-fat" dieters. This group was compared with a higher-fat group comprising 25 active participants and only 6 dropouts. Forty additional dropouts were not "available for measurements." Based purely on research showing the powerful impact of active participation in weight-loss programs, 67% of the low-fat group included in the primary analyses would be expected to fare poorly, compared with 19% of the low-carb group. (13) This differential subject attrition, one of the primary threats to internal validity, was statistically very significant (P .001) but ignored by the authors. When the researchers compared only current participants (excluding dropouts), the groups did not differ in weight loss. ... The McManus and Yancy low-fat participants prematurely discontinued treatment almost twice as often (43%) as their low-carbohydrate groups (24%). Unlike McManus et al, however, Yancy et al did not analyze the data separately for completers only. Without taking into account the likely poorer performance of the greater number of dropouts in the low-fat group, Yancy et al may have inadvertently skewed the results in favor of their low-carbohydrate group. I agree that the low-carb study authors shouldn't have ignored differential attrition, but on the other hand, if twice as many subjects can't even stick to a 'moderate-fat' program, how do the authors of this paper think they're all going to stick to a very low fat program? Isn't the ability of people to maintain a way of eating somewhat relevant? I totally believe that if you locked me in a room and fed me nothing but white rice, I'd lose weight on a high-carb diet. The thing is, I'm not locked in a room with nothing but rice, I'm out in the real world, and whatever dietary manipulations I use to maintain a healthy weight have to be something I can actually do in that environment. That's really my peeve with low-fat low-calorie dieting - I can definitely lose weight on it, I'm just miserable the entire time. I lost weight that way at one point, quite a bit, through iron willpower and the constant support of a friend. God, I remember the stuff I ate - all those salads with weird-tasting low-fat dressing, baked corn chips with low-fat cheese, Snackwells cookies.... oh yick. And I was *always* hungry. Beth |
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Jbuch wrote:
:: :: This whole diet industry is starting to sound repulsive as ways for :: the diet plan proponents to put their agenda before that of the :: client. :: Sounds just like religion & politics. |
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Very-low-fat diets are superior to low-carbohydrate diets (***sigh!***)
Roger Zoul wrote:
Jbuch wrote: :: :: This whole diet industry is starting to sound repulsive as ways for :: the diet plan proponents to put their agenda before that of the :: client. :: Sounds just like religion & politics. Exactly. If there's money to be made, that will always trump what is really best for people. Hence, people need to learn for themselves and not rely on "official" pronouncements. |
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