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Medscape on dieting
Medscape is running a series of articles with a sensible overview of
weight-reduction schemes. Here's the first part in the series. See the link at the end for the references. I don't plan on posting the remaining parts. Note: Medscape requires registration, but is free. Making Scientific Sense of Different Dietary Approaches, Part 1: Meeting Dietary Needs, Achieving Weight Loss George L. Blackburn, MD, PhD Medscape Diabetes & Endocrinology 6(1), 2004. c 2004 Medscape Posted 02/26/2004 Introduction The greater the prevalence of obesity, the more compelling the allure of dietary approaches that promise fast and relatively easy weight loss. Diets are big news in the United States, where 63% of men and 55% of women are overweight or obese.[1] They're also big business -- a $30 billion a year industry[2] made up of products and services that run the gamut from videos to supplements to sugar-free ice cream. Though some of these offerings are based on good science and are safe and effective, most are nothing more than useless, while still others are untested or even dangerous. Desperate dieters, however, are quick to believe anecdotal accounts and unsubstantiated claims of quick success. Those who fail to achieve their ideal of svelte good health often wind up as part of another burgeoning market: the $92.6 billion (in 2002 dollars) in annual medical expenditures attributed to overweight and obesity -- a figure up from $78.5 billion in 1998.[3] Public health recommendations call for weight loss in those who are overweight and have associated medical conditions and in those who are obese. The optimal means to that end, however, is a subject of great controversy in both the lay press and the medical literature. Even the U.S. Department of Agriculture's Food Guide Pyramid,[4] developed to help Americans make dietary choices that maintain good health and reduce the risk of chronic disease, has been under scrutiny and is in the process of being revised. Current Consensus The current consensus is that obesity in most individuals is a multifactorial disorder caused by a combination of environmental and genetic factors. Despite the complexities of investigating gene/environment interactions, scientific evidence suggests that genetic variation influences the ability to lose weight, the total amount of fat lost, the preferential reduction of abdominal fat stores, and changes in disease risk factors in response to alterations in energy balance. The balance between energy intake and energy expenditure, which is regulated by interactions between environmental and genetic factors, determines body weight. Family-based and case-control studies suggest that genetic variation affects responses to environmental and lifestyle changes in energy balance. Maintenance of stable body weight is achieved via a biological process known as energy homeostasis, which matches cumulative energy intake to expenditure over time. Energy homeostasis involves humoral signals, such as leptin, that create a circuit between peripheral tissues involved in energy storage and utilization and central networks controlling energy balance. Obesity is the most common disorder of energy homeostasis, and because of its increasing prevalence and strong links to metabolic and cardiovascular diseases, is a leading cause of mortality worldwide.[5] Understanding how defects in this homeostatic system cause obesity is critical for the development of new and more effective forms of therapy.[6,7] Wide Variations in Individual Responses Fat, if eaten in excess of energy needs, will make a person overweight or obese. So will excess intake of carbohydrates. The Evidence-based Guidelines issued by the National Institutes of Health[8,9] call for weight loss by simultaneously restricting caloric intake and increasing physical activity.[10] Many studies demonstrate that obese adults can lose about 1 lb per week and achieve a 5% to 15% weight loss by consuming 500 to 1000 kcal a day less than the caloric intake required for the maintenance of their current weight[8,9] -- a goal that can be best achieved by reducing portion sizes, minimizing snacks and desserts, and replacing high-fat and high-calorie foods with lower-fat and lower-calorie choices. Weight loss, achieved via caloric restriction and increased physical activity, is the most common treatment prescribed for obesity. Adherence -- measured by such variables as number of weight loss classes attended, degree of caloric deficit, and length of time spent exercising -- has a partial influence on outcomes. But even under controlled experimental conditions with complete adherence, changes in energy balance result in wide heterogeneity in responses. Studies suggest considerable interindividual variation in response to standardized obesity treatments. For example, in middle-aged women, a 16-week, 1200 kcal/day diet resulted in an average weight loss of 9.6 } 3.0 kg (10.7% of initial body weight), with a wide range of weight loss from 6.5% to 16.7% of initial body weight.[11] Controlled energy deficit interventions showed similar heterogeneity. For example, the amount of fat lost, measured by dual energy x-ray absorptiometry (DXA), ranged from 3.1-12.4 kg in young women fed a very low-calorie diet (382 kcal/day) for 28 days on an inpatient unit.[12,13] In young men, the mean loss of body weight after a total energy deficit of 58,317 kcal induced by exercise training was 5 kg, with a range of 1-8 kg.[14] Experimental as well as clinical data support these outcomes. Among 9 different strains of mice subjected to a high-fat diet for 7 weeks, there was a 6-fold difference in adiposity gain between the most sensitive and the most resistant strains.[15] In young men, overfeeding by 1000 kcal/day for 100 days resulted in a mean weight gain of 8.1 kg, but also a 3-fold difference between the highest and lowest gainers.[16] Similarly, overfeeding men and women by 1000 kcal/day for 8 weeks resulted in a range of weight gain from 1.4-7.2 kg, along with a 10-fold difference (58-687 kcal/day) in fat storage.[17] The Latest Recommended Daily Allowances (RDAs) New RDAs for fat, protein, and carbohydrates[18] broaden the recommended ranges for consuming these nutrients compared with earlier guidelines. Whereas the latter called for diets with 50% or more of calories from carbohydrates and 30% or less from fat, the most recent adult reference intakes specify 45% to 65% of calories from carbohydrates, 20% to 35% from fat, and 10% to 35% from protein. New guidelines for children are similar to those for adults, except for a slight increase in the proportion of fat (25% to 40% of caloric intake) recommended for infants and young children. The minimum for carbohydrates -- 130 grams per day -- is based on the least amount needed to produce enough glucose for the brain to function; most people, however, regularly consume more than that. The upper limit for added sugars (ie, those found in candy, soft drinks, fruit drinks, pastries, and other sweets) is 25% of total calories; evidence indicates that people whose diets are high in such sugars have lower intakes of essential nutrients. Overview of Macronutrients Dietary Fat Fat is a major source of energy for the body and aids in the absorption of essential vitamins. Dietary fats -- either saturated, monounsaturated, or polyunsaturated -- are typically found in butter, margarine, vegetable oils, visible fat on meat and poultry, whole milk, egg yolks, and nuts. Saturated fats -- usually found in meats, baked goods, fast food, and full dairy products -- can raise low-density lipoprotein (LDL)-cholesterol levels and risk of heart attack in certain individuals; so can trans fatty acids, a form of unsaturated fat used in many margarines and shortenings. Saturated fats are of no known benefit in preventing chronic disease, nor are they required at any level in the diet. Because they occur in so many types of foods, however, an all-out ban would make it very difficult to meet other nutritional requirements. Monounsaturated and polyunsaturated fatty acids reduce blood cholesterol as well as risk of heart disease. Omega-3 (alpha-linolenic) and omega-6 (linoleic) polyunsaturated fatty acids are essential nutrients not synthesized in the body. The former is found in milk and some vegetable oils (eg, soybean and flaxseed); the latter in vegetable oils (eg, safflower and corn oil). Recommended daily intakes for alpha-linolenic acid are 1.6 grams for men and 1.1 grams for women; recommended intakes for linoleic acid are 17 grams for men and 12 grams for women. Dietary Protein The latest RDAs establish age-based requirements for the 9 essential amino acids found in dietary protein, as well as values for pregnant women, infants, and children. The recommended level of protein intake for adults remains unchanged at 0.8 g/kg of body weight. There are no upper intake levels for protein or the individual amino acids because of often-conflicting or inadequate data on the potential for high protein diets to produce chronic or other diseases. Given a lack of data on overconsumption of some amino acids and protein, the new guidelines also recommend caution in consuming levels of these nutrients significantly above those normally found in foods. Dietary Fiber Dietary fiber can be found in such foods as cereal bran, sweet potatoes, and legumes. Pectin, extracted from citrus peel and used as a gel basis for jams and jellies, is an example of functional fiber, which is isolated or extracted from natural sources or is synthetic. Recommended intake levels for fiber, the first established by the Food and Nutrition Board, are based on studies that show an association between low-fiber diets and increased risk for heart disease. Other data, though still inconclusive, suggest that fiber also may aid in weight control and help prevent colon cancer. For adults 50 years of age or younger, the recommended daily intake for total fiber (dietary and functional) is 38 grams for men and 25 for women; for men and women over age 50, the figures are 30 and 21 grams per day, respectively.[18] Effects of Macronutrient Intake on Appetite and Energy Balance Macronutrient intake is one of many factors (eg, neurochemical, gastric hormone, environmental, emotional) that influence hunger, appetite, and subsequent food intake -- often on a meal-to-meal basis. Study results on the effects of macronutrients on appetite and energy balance are summarized below. Dietary fat: A number of studies report high degrees of satisfaction and satiety in subjects on low-fat diets.[19,20] One study found greater compliance and reduced binge eating on a low-fat diet compared with a low-calorie diet.[21] A randomized crossover study on voluntary food consumption in identical twins found that dietary fat had no significant effect on energy intake; however, analysis of individual foods matched for energy density, palatability, and fiber showed that energy density and palatability were significant determinants of energy intake.[22] Dietary protein: Ten protein preload studies examined the effects of dietary protein and other macronutrients on later energy intake.[23-28] In 8 of 10 studies, energy intake was lower after the high-protein preload than it was after the preloads containing the other macronutrients; mean energy intake was about 9% less with the high-protein preload. Other data suggest that weight loss from a high-protein diet produces a smaller decline in energy expenditure than that from a high-carbohydrate diet. Short-term studies indicate that dietary protein modulates energy intake via the sensation of satiety and raises total energy expenditure by increasing the thermic effect of feeding. In studies of diets with fixed energy intake, satiety and thermic effects did not contribute to weight and fat loss.[29] Data on body fat loss with ad libitum consumption on high-protein diets are limited. One 6-month randomized trial comparing 2 ad libitum reduced-fat diets (30% of total energy) found that subjects on a high-protein diet (25% of total energy) consumed 18% fewer calories than those on a high-carbohydrate diet (protein 12% of total energy). The group consuming the high-protein diet also achieved the greatest fat reduction and weight loss (8.9 kg vs 5.1kg for the high-carbohydrate group).[30] Dietary fiber: The majority of studies on soluble or insoluble fiber indicate that increased intake of either nutrient raises postmeal satiety and reduces subsequent hunger. Data from studies on ad libitum diets indicate that consumption of an additional 14 grams per day of fiber for 2 days is associated with a mean decrease in energy intake of 10% and a mean weight loss of 1.9 kg over 3.8 months. Increased fiber consumption also appears to reduce energy intake and increase body weight loss in individuals with obesity.[31] Conclusion The latest dietary reference intakes specify how to meet energy and nutritional needs while minimizing risk of chronic disease. For adults, 45% to 65% of daily calories should come from carbohydrates; 20% to 35% from fat; and 10% to 35% from protein. Acceptable RDAs for children are similar to those for adults, except that infants and younger children need a slightly higher proportion of fat, ie, 25% to 40% of their caloric intake. Carbohydrate, fat, and protein all serve as energy sources, and, to some extent, can be substituted for one another to meet caloric needs.[18] Part 2 of this column will discuss specific dietary approaches, including a review of the data on low-carbohydrate, high-protein diets; structured meal plans; and dairy products and weight control. References (see http://www.medscape.com/viewarticle/469768_print) -- Tabi Kasanari |
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Medscape on dieting
[cut]
The minimum for carbohydrates -- 130 grams per day -- is based on the least amount needed to produce enough glucose for the brain to function; [cut] They really need to stop saying this, as it absolutely is not true, and I can verify by over a year of low carbing. Overview of Macronutrients Dietary Fat Fat is a major source of energy for the body and aids in the absorption of essential vitamins. Dietary fats -- either saturated, monounsaturated, or polyunsaturated -- are typically found in butter, margarine, vegetable oils, visible fat on meat and poultry, whole milk, egg yolks, and nuts. Saturated fats -- usually found in meats, baked goods, fast food, and full dairy products -- can raise low-density lipoprotein (LDL)-cholesterol levels and risk of heart attack in certain individuals; They really need to stop saying this too. I never avoid saturated fats, yet I've increased my HDL (also increased LDL slightly, but lowered my total chol./HDL ratio). -- Bob in CT Remove ".x" to reply |
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Medscape on dieting
On Tue, 2 Mar 2004 13:17:50 GMT, "Tabi Kasanari"
wrote: Medscape is running a series of articles with a sensible overview of weight-reduction schemes. Here's the first part in the series. See the link at the end for the references. I don't plan on posting the remaining parts. Good grief, I don't guess you've been following the discussions on copyright violations, have you? Here's a refresher on the terms you agreed to when you signed up for Medscape access: Copyright We or our partners own the information on Medscape.com. In fact, the entire contents and design of Medscape.com are protected under U.S. and international copyright laws. You may look at our Web site online, download individual articles to your personal or handheld computer for later reading, and even print a reasonable number of copies of pages for yourself, your family, or friends. You must not remove any copyright notices from our materials. We reserve all our other rights. Among other things, this means you must not sell our information, rewrite or modify it, redistribute it, put it on your own Web site, or use it for any commercial purpose without our prior written permission. Post a link to the article and/or short exceprts for discussion. Posting the entire article as you did is a copyright violation and also violates your agreement with Medscape. |
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Medscape on dieting
Bob in CT wrote:
:: [cut] ::: ::: The minimum for carbohydrates -- 130 grams per day -- is based on ::: the least ::: amount needed to produce enough glucose for the brain to function; :: [cut] :: :: They really need to stop saying this, as it absolutely is not true, :: and I can verify by over a year of low carbing. Agreed.....total nonsense....and do they not know about protein conversion to glucose? :: ::: Overview of Macronutrients ::: Dietary Fat ::: Fat is a major source of energy for the body and aids in the ::: absorption of ::: essential vitamins. Dietary fats -- either saturated, ::: monounsaturated, or polyunsaturated -- are typically found in ::: butter, margarine, vegetable oils, ::: visible fat on meat and poultry, whole milk, egg yolks, and nuts. ::: ::: Saturated fats -- usually found in meats, baked goods, fast food, ::: and full ::: dairy products -- can raise low-density lipoprotein ::: (LDL)-cholesterol levels ::: and risk of heart attack in certain individuals; :: :: They really need to stop saying this too. I never avoid saturated :: fats, yet I've increased my HDL (also increased LDL slightly, but :: lowered my total chol./HDL ratio). Agreed again. |
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Medscape on dieting
[cut] The minimum for carbohydrates -- 130 grams per day -- is based on the least amount needed to produce enough glucose for the brain to function; [cut] They really need to stop saying this, as it absolutely is not true, and I can verify by over a year of low carbing. Nah. They'll just say that you're too stupid to eat enough carbs because your brain obviously isn't functioning. I know, I know, I too could swear that I have full cognitive powers, but must be wrong. "They" say so. LCing since 12/01/03- Me- 265/224/140 & hubby- 310/246/180 |
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Medscape on dieting
The minimum for carbohydrates -- 130 grams per day -- is based on the least amount needed to produce enough glucose for the brain to function; [cut] They really need to stop saying this, as it absolutely is not true, and I can verify by over a year of low carbing. Wow, my brain hasn't functioned for six months? That's news to my employer, friends, relatives, whatever...I thought it was working better. Marsha/Ohio |
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Medscape on dieting
LCer09 wrote:
Nah. They'll just say that you're too stupid to eat enough carbs because your brain obviously isn't functioning. I know, I know, I too could swear that I have full cognitive powers, but must be wrong. "They" say so. LCing since 12/01/03- Me- 265/224/140 & hubby- 310/246/180 FYI, "They" At the end of the first Medscape article I read: Funding Information This column is supported by an unrestricted educational grant from Slim-Fast. -- Rudy - Remove the Z from my address to respond. "It is better to die on your feet than to live on your knees!" -Emiliano Zapata Check out the a.s.d.l-c FAQ at: http://www.grossweb.com/asdlc/faq.htm |
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