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low-carb kicks butt in studies - again
http://www.cnn.com/2004/HEALTH/diet....eut/index.html
Headline from CNN: Reports: Low-carb has mixed results Tuesday, May 18, 2004 Posted: 8:55 AM EDT (1255 GMT) WASHINGTON (Reuters) -- Low-carbohydrate diets help people lose weight in the short term but work no better than other diets after a year, researchers reported on Monday. The actual abstracts, read the conclusions: ******* A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia A Randomized, Controlled Trial William S. Yancy, Jr., MD, MHS; Maren K. Olsen, PhD; John R. Guyton, MD; Ronna P. Bakst, RD; and Eric C. Westman, MD, MHS 18 May 2004 | Volume 140 Issue 10 | Pages 769-777 Background: Low-carbohydrate diets remain popular despite a paucity of scientific evidence on their effectiveness. Objective: To compare the effects of a low-carbohydrate, ketogenic diet program with those of a low-fat, low-cholesterol, reduced-calorie diet. Design: Randomized, controlled trial. Setting: Outpatient research clinic. Participants: 120 overweight, hyperlipidemic volunteers from the community. Intervention: Low-carbohydrate diet (initially, 20 g of carbohydrate daily) plus nutritional supplementation, exercise recommendation, and group meetings, or low-fat diet (30% energy from fat, 300 mg of cholesterol daily, and deficit of 500 to 1000 kcal/d) plus exercise recommendation and group meetings. Measurements: Body weight, body composition, fasting serum lipid levels, and tolerability. Results: A greater proportion of the low-carbohydrate diet group than the low-fat diet group completed the study (76% vs. 57%; P = 0.02). At 24 weeks, weight loss was greater in the low-carbohydrate diet group than in the low-fat diet group (mean change, –12.9% vs. –6.7%; P 0.001). Patients in both groups lost substantially more fat mass (change, –9.4 kg with the low-carbohydrate diet vs. –4.8 kg with the low-fat diet) than fat-free mass (change, –3.3 kg vs. –2.4 kg, respectively). Compared with recipients of the low-fat diet, recipients of the low-carbohydrate diet had greater decreases in serum triglyceride levels (change, –0.84 mmol/L vs. –0.31 mmol/L [–74.2 mg/dL vs. –27.9 mg/dL]; P = 0.004) and greater increases in high-density lipoprotein cholesterol levels (0.14 mmol/L vs. –0.04 mmol/L [5.5 mg/dL vs. –1.6 mg/dL]; P 0.001). Changes in low-density lipoprotein cholesterol level did not differ statistically (0.04 mmol/L [1.6 mg/dL] with the low-carbohydrate diet and –0.19 mmol/L [–7.4 mg/dL] with the low-fat diet; P = 0.2). Minor adverse effects were more frequent in the low-carbohydrate diet group. Limitations: We could not definitively distinguish effects of the low-carbohydrate diet and those of the nutritional supplements provided only to that group. In addition, participants were healthy and were followed for only 24 weeks. These factors limit the generalizability of the study results. Conclusions: Compared with a low-fat diet, a low-carbohydrate diet program had better participant retention and greater weight loss. During active weight loss, serum triglyceride levels decreased more and high-density lipoprotein cholesterol level increased more with the low-carbohydrate diet than with the low-fat diet. ************** The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial Linda Stern, MD; Nayyar Iqbal, MD; Prakash Seshadri, MD; Kathryn L. Chicano, CRNP; Denise A. Daily, RD; Joyce McGrory, CRNP; Monica Williams, BS; Edward J. Gracely, PhD; and Frederick F. Samaha, MD 18 May 2004 | Volume 140 Issue 10 | Pages 778-785 Background: A previous paper reported the 6-month comparison of weight loss and metabolic changes in obese adults randomly assigned to either a low-carbohydrate diet or a conventional weight loss diet. Objective: To review the 1-year outcomes between these diets. Design: Randomized trial. Setting: Philadelphia Veterans Affairs Medical Center. Participants: 132 obese adults with a body mass index of 35 kg/m2 or greater; 83% had diabetes or the metabolic syndrome. Intervention: Participants received counseling to either restrict carbohydrate intake to 30 g per day (low-carbohydrate diet) or to restrict caloric intake by 500 calories per day with 30% of calories from fat (conventional diet). Measurements: Changes in weight, lipid levels, glycemic control, and insulin sensitivity. Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). For persons on the low-carbohydrate diet, triglyceride levels decreased more (P = 0.044) and high-density lipoprotein cholesterol levels decreased less (P = 0.025). As seen in the small group of persons with diabetes (n = 54) and after adjustment for covariates, hemoglobin A1c levels improved more for persons on the low-carbohydrate diet. These more favorable metabolic responses to a low-carbohydrate diet remained significant after adjustment for weight loss differences. Changes in other lipids or insulin sensitivity did not differ between groups. Limitations: These findings are limited by a high dropout rate (34%) and by suboptimal dietary adherence of the enrolled persons. Conclusion: Participants on a low-carbohydrate diet had more favorable overall outcomes at 1 year than did those on a conventional diet. Weight loss was similar between groups, but effects on atherogenic dyslipidemia and glycemic control were still more favorable with a low-carbohydrate diet after adjustment for differences in weight loss. ****** Low-carb outperformed low-fat in both studies, both in weight loss and in lipid profile improvement and yet the headline suggests that this was "mixed results". Another example of studies showing clear results and the purveyors of the message changing the message entirely. Now we have scientific evidence that low-carb works and is healthy over a one year period. TC |
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low-carb kicks butt in studies - again
I always wonder how they call 2 kg, about 4 pounds, not significant. It's
pretty darn significant in my life! Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). -- Bob in CT Remove ".x" to reply |
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low-carb kicks butt in studies - again
"Bob in CT" wrote in message news I always wonder how they call 2 kg, about 4 pounds, not significant. It's pretty darn significant in my life! Actually (in case you weren't just joking), the scientific method employs a test of statistical significance to account for variables not included (and therefore not controlled) in the studies between two groups. Thus, there can be a difference that mathematically may not be statistically significant because of these factors. Oops! Sorry! I've been reading "Scientific American. |
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low-carb kicks butt in studies - again
On 5/18/2004 10:32 AM, Bob in CT wrote:
I always wonder how they call 2 kg, about 4 pounds, not significant. It's pretty darn significant in my life! Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). If you are maintaining that is probably the range that you are working within. -- jmk in NC |
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low-carb kicks butt in studies - again
Bob in CT wrote in
news Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). I always wonder how they call 2 kg, about 4 pounds, not significant. It's pretty darn significant in my life! In statistics, "significant" doesn't mean "personally meaningful." In this case, it means that there would be a 20% chance of finding a difference of at least 1.9 kg purely as a result of "luck of the draw" in choosing these particular samples, even if there were no difference in the underlying populations. In other words, you don't have a whole lot of confidence that you'd be able to replicate that particular result. |
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low-carb kicks butt in studies - again
On Tue, 18 May 2004 09:47:03 -0500, Jim Bard wrote:
"Bob in CT" wrote in message news I always wonder how they call 2 kg, about 4 pounds, not significant. It's pretty darn significant in my life! Actually (in case you weren't just joking), the scientific method employs a test of statistical significance to account for variables not included (and therefore not controlled) in the studies between two groups. Thus, there can be a difference that mathematically may not be statistically significant because of these factors. Oops! Sorry! I've been reading "Scientific American. That is true, but sometimes the math should be damned. 4 pounds is significant. Granted, the analysis includes "11 to 19 pounds (5 to 9 kg) for the low-carb group and 7 to 19 pounds (3 to 9 kg) for the low-fat group," so the ranges overlap. However, if the average is 4 pounds, that's significant. And this, of course, depends on what type of "average" they were taking. I assume it's the mean and not the median. Also, there's no indication in the CNN article that they took bodyfat measurements. I'd hazard a guess that the overall fat loss of the low carb was greater than the fat loss of the low fat. -- Bob in CT Remove ".x" to reply |
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low-carb kicks butt in studies - again
Bob in CT wrote:
I always wonder how they call 2 kg, about 4 pounds, not significant. It's pretty darn significant in my life! That's not what makes a difference significant though. Think of it like this... suppose there's a factory that makes a widget with an average weight of 1.5 lbs, but is supposed to vary in size from 1 - 2 lbs. On average, you'd expect any individual widget to weigh 1.5 lbs. It you weigh one and it weighs 2 lbs, that's not surprising, you know it's *supposed* to have that much variance. But if you weigh 10 items, and the average weight of those 10 is 2 lbs, you start to get suspicious that something is wrong. If you measure 100 and they average is a 2 lb weight, you're almost certain something is wrong. If you measure 1000 and the average weight is 2 lbs, something is almost *definetly* wrong. The significance of your conslusion that something is wrong increases with the sample size. Given that retooling a factory is an expensive proposition, you want to be pretty sure about the error before fixing it. In each case of testing, you're comparing a sample to the whole population and guessing what is true about that population based on the sample. In the case of one sample, you're not very sure about the population at all, but in the case of 100 samples, you have more certainty about what is going on. There's mathematical formulas from statistics that basically measure how significant a measurement is, how likely it is that a sample describes the population. My example shows that sample size is one variable in such equations, but there's other variables as well... for example, how much consistency there is in a bunch of measurements. It's not about the size of the measurement at all... I can rewrite the above example to use micrograms or tons instead of pounds and the example still works. It's about how likely a set of limited measurements correlates to the entire population (most of which you haven't measured). Significance is basically a measure of how confident you can be that a particular conclusion is actually true, not how big the conclusion itself is. Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). p = 0.20 is a description of the measurable significance, and this is a very low measure, comparable to just one widget's weight being off in our example above. It means they consider this to possibly be just luck and can't know if it's real for the population without more study. p = 1 means that something is 100%, absolutely, certainly true - you can't ever get p = 1 short of measuring the entire population. And measuring the entire population isn't doing an experiment anymore, that is life, the universe and everything. Generally, a scientist wants p 0.90 or 0.95 or 0.99. Which cut-off is acceptable depends on the specific type of study. But p = 0.2 *definetly* is not good enough to say the differences between those groups is true (for that particular measurement, other measurments in the study are significant). So in summary, they are saying they measured a difference, but the difference isn't meaningful enough to signify anything beyond what happened to their sample. -- As you accelerate your food, it takes exponentially more and more energy to increase its velocity, until you hit a limit at C. This energy has to come from somewhere; in this case, from the food's nutritional value. Thus, the faster the food is, the worse it gets. -- Mark Hughes, comprehending the taste of fast food |
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low-carb kicks butt in studies - again
On 18 May 2004 14:58:35 GMT, Eric Bohlman wrote:
Bob in CT wrote in news Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). I always wonder how they call 2 kg, about 4 pounds, not significant. It's pretty darn significant in my life! In statistics, "significant" doesn't mean "personally meaningful." In this case, it means that there would be a 20% chance of finding a difference of at least 1.9 kg purely as a result of "luck of the draw" in choosing these particular samples, even if there were no difference in the underlying populations. In other words, you don't have a whole lot of confidence that you'd be able to replicate that particular result. That is true, but P values can be overrated. If you get one that's 0.001, does that mean that it's always going to be reproduced? From what I've seen, no. One study will have certain results and another will have the opposite results, and both will have P values that make them seem great. Personally, I think that 4 pounds is significant, and I don't think that a P value of 0.2 means that it's not significant. Of course, there's no real data here -- perhaps two people lost 19 pounds on low carb while only one person lost 19 pounds onlow fat. So, you can't really see what's going on without access to the data. -- Bob in CT Remove ".x" to reply |
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low-carb kicks butt in studies - again
tcomeau wrote:
snip abstracts of two studies Ah, this has more info than the media reports. There's the expected results that the lipid profiles and glycemic control of low-carbers prove low-carb is the healthier diet, but there's other important bits. First, the low-carb diet in each study did not include calorie restriction, whereas the low-fat diet *did*. Thus the fact that low-carbers actually ate fewer calories than low-fatters is a significant effect of the diet itself. You eat fewer calories without trying. Good stuff for weight loss. Secondly is the retention rate. It is not broken down in the second study, but is in the first study. Three quarters of the low-carbers completed the first study as opposed to only half the low-fatters. since I assume these groups had no large differences in willpower, it appears that much less "butching up" is necessary on low-carb. These studies together show that a low-carb diet is both healthier and easier than a low-calorie/low-fat diet. -- As you accelerate your food, it takes exponentially more and more energy to increase its velocity, until you hit a limit at C. This energy has to come from somewhere; in this case, from the food's nutritional value. Thus, the faster the food is, the worse it gets. -- Mark Hughes, comprehending the taste of fast food |
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low-carb kicks butt in studies - again
A couple of things not mentioned in this version of the research. 1. By your guidelines the first must be tossed, it had atkins grant money involved. The first also was only 24 weeks, the second reflects other similar research, after 1 year weight status was not significantly different. The most intresting results, again reflecting other such research, is that trigs are lower and hdl higher in lc. 2. By the end the daily calorie intake was similar, in the year long study, the lead researcher says: " Dr. Linda Stern, who led the study, said it confirmed that any diet that cuts calories will work. "Americans are overweight because we're eating too much food and ingesting too many calories," she said in a statement." Also of interest is the high drop out rate in both diets in both studies and the compliance problem. This too reflects that most people fail after a time in maintaining weight status regardless of diet approach, either these two diet types or others. http://www.cnn.com/2004/HEALTH/diet....eut/index.html Headline from CNN: Reports: Low-carb has mixed results Tuesday, May 18, 2004 Posted: 8:55 AM EDT (1255 GMT) WASHINGTON (Reuters) -- Low-carbohydrate diets help people lose weight in the short term but work no better than other diets after a year, researchers reported on Monday. The actual abstracts, read the conclusions: ******* A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia A Randomized, Controlled Trial William S. Yancy, Jr., MD, MHS; Maren K. Olsen, PhD; John R. Guyton, MD; Ronna P. Bakst, RD; and Eric C. Westman, MD, MHS 18 May 2004 | Volume 140 Issue 10 | Pages 769-777 Background: Low-carbohydrate diets remain popular despite a paucity of scientific evidence on their effectiveness. Objective: To compare the effects of a low-carbohydrate, ketogenic diet program with those of a low-fat, low-cholesterol, reduced-calorie diet. Design: Randomized, controlled trial. Setting: Outpatient research clinic. Participants: 120 overweight, hyperlipidemic volunteers from the community. Intervention: Low-carbohydrate diet (initially, 20 g of carbohydrate daily) plus nutritional supplementation, exercise recommendation, and group meetings, or low-fat diet (30% energy from fat, 300 mg of cholesterol daily, and deficit of 500 to 1000 kcal/d) plus exercise recommendation and group meetings. Measurements: Body weight, body composition, fasting serum lipid levels, and tolerability. Results: A greater proportion of the low-carbohydrate diet group than the low-fat diet group completed the study (76% vs. 57%; P = 0.02). At 24 weeks, weight loss was greater in the low-carbohydrate diet group than in the low-fat diet group (mean change, 12.9% vs. 6.7%; P 0.001). Patients in both groups lost substantially more fat mass (change, 9.4 kg with the low-carbohydrate diet vs. 4.8 kg with the low-fat diet) than fat-free mass (change, 3.3 kg vs. 2.4 kg, respectively). Compared with recipients of the low-fat diet, recipients of the low-carbohydrate diet had greater decreases in serum triglyceride levels (change, 0.84 mmol/L vs. 0.31 mmol/L [74.2 mg/dL vs. 27.9 mg/dL]; P = 0.004) and greater increases in high-density lipoprotein cholesterol levels (0.14 mmol/L vs. 0.04 mmol/L [5.5 mg/dL vs. 1.6 mg/dL]; P 0.001). Changes in low-density lipoprotein cholesterol level did not differ statistically (0.04 mmol/L [1.6 mg/dL] with the low-carbohydrate diet and 0.19 mmol/L [7.4 mg/dL] with the low-fat diet; P = 0.2). Minor adverse effects were more frequent in the low-carbohydrate diet group. Limitations: We could not definitively distinguish effects of the low-carbohydrate diet and those of the nutritional supplements provided only to that group. In addition, participants were healthy and were followed for only 24 weeks. These factors limit the generalizability of the study results. Conclusions: Compared with a low-fat diet, a low-carbohydrate diet program had better participant retention and greater weight loss. During active weight loss, serum triglyceride levels decreased more and high-density lipoprotein cholesterol level increased more with the low-carbohydrate diet than with the low-fat diet. ************** The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial Linda Stern, MD; Nayyar Iqbal, MD; Prakash Seshadri, MD; Kathryn L. Chicano, CRNP; Denise A. Daily, RD; Joyce McGrory, CRNP; Monica Williams, BS; Edward J. Gracely, PhD; and Frederick F. Samaha, MD 18 May 2004 | Volume 140 Issue 10 | Pages 778-785 Background: A previous paper reported the 6-month comparison of weight loss and metabolic changes in obese adults randomly assigned to either a low-carbohydrate diet or a conventional weight loss diet. Objective: To review the 1-year outcomes between these diets. Design: Randomized trial. Setting: Philadelphia Veterans Affairs Medical Center. Participants: 132 obese adults with a body mass index of 35 kg/m2 or greater; 83% had diabetes or the metabolic syndrome. Intervention: Participants received counseling to either restrict carbohydrate intake to 30 g per day (low-carbohydrate diet) or to restrict caloric intake by 500 calories per day with 30% of calories from fat (conventional diet). Measurements: Changes in weight, lipid levels, glycemic control, and insulin sensitivity. Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was 5.1 ± 8.7 kg compared with 3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (1.9 kg [95% CI, 4.9 to 1.0 kg]; P = 0.20). For persons on the low-carbohydrate diet, triglyceride levels decreased more (P = 0.044) and high-density lipoprotein cholesterol levels decreased less (P = 0.025). As seen in the small group of persons with diabetes (n = 54) and after adjustment for covariates, hemoglobin A1c levels improved more for persons on the low-carbohydrate diet. These more favorable metabolic responses to a low-carbohydrate diet remained significant after adjustment for weight loss differences. Changes in other lipids or insulin sensitivity did not differ between groups. Limitations: These findings are limited by a high dropout rate (34%) and by suboptimal dietary adherence of the enrolled persons. Conclusion: Participants on a low-carbohydrate diet had more favorable overall outcomes at 1 year than did those on a conventional diet. Weight loss was similar between groups, but effects on atherogenic dyslipidemia and glycemic control were still more favorable with a low-carbohydrate diet after adjustment for differences in weight loss. ****** Low-carb outperformed low-fat in both studies, both in weight loss and in lipid profile improvement and yet the headline suggests that this was "mixed results". Another example of studies showing clear results and the purveyors of the message changing the message entirely. Now we have scientific evidence that low-carb works and is healthy over a one year period. TC |
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