Thu, Jun-28-12, 02:26
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Plan: Muscle Centric
Stats: 238/153/160
BF:
Progress: 109%
Location: UK
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Quote:
Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance
Cara B. Ebbeling, PhD; Janis F. Swain, MS, RD; Henry A. Feldman, PhD; William W. Wong, PhD; David L. Hachey, PhD; Erica Garcia-Lago, BA; David S. Ludwig, MD, PhD
ABSTRACT
Context Reduced energy expenditure following weight loss is thought to contribute to weight gain. However, the effect of dietary composition on energy expenditure during weight-loss maintenance has not been studied.
Objective To examine the effects of 3 diets differing widely in macronutrient composition and glycemic load on energy expenditure following weight loss.
Design, Setting, and Participants A controlled 3-way crossover design involving 21 overweight and obese young adults conducted at Children's Hospital Boston and Brigham and Women's Hospital, Boston, Massachusetts, between June 16, 2006, and June 21, 2010, with recruitment by newspaper advertisements and postings.
Intervention After achieving 10% to 15% weight loss while consuming a run-in diet, participants consumed an isocaloric low-fat diet (60% of energy from carbohydrate, 20% from fat, 20% from protein; high glycemic load), low–glycemic index diet (40% from carbohydrate, 40% from fat, and 20% from protein; moderate glycemic load), and very low-carbohydrate diet (10% from carbohydrate, 60% from fat, and 30% from protein; low glycemic load) in random order, each for 4 weeks.
Main Outcome Measures Primary outcome was resting energy expenditure (REE), with secondary outcomes of total energy expenditure (TEE), hormone levels, and metabolic syndrome components.
Results Compared with the pre–weight-loss baseline, the decrease in REE was greatest with the low-fat diet (mean [95% CI], –205 [–265 to –144] kcal/d), intermediate with the low–glycemic index diet (–166 [–227 to –106] kcal/d), and least with the very low-carbohydrate diet (−138 [–198 to –77] kcal/d; overall P = .03; P for trend by glycemic load = .009). The decrease in TEE showed a similar pattern (mean [95% CI], −423 [–606 to –239] kcal/d; −297 [–479 to –115] kcal/d; and −97 [–281 to 86] kcal/d, respectively; overall P = .003; P for trend by glycemic load < .001). Hormone levels and metabolic syndrome components also varied during weight maintenance by diet (leptin, P < .001; 24-hour urinary cortisol, P = .005; indexes of peripheral [P = .02] and hepatic [P = .03] insulin sensitivity; high-density lipoprotein [HDL] cholesterol, P < .001; non-HDL cholesterol, P < .001; triglycerides, P < .001; plasminogen activator inhibitor 1, P for trend = .04; and C-reactive protein, P for trend = .05), but no consistent favorable pattern emerged.
Conclusion Among overweight and obese young adults compared with pre–weight-loss energy expenditure, isocaloric feeding following 10% to 15% weight loss resulted in decreases in REE and TEE that were greatest with the low-fat diet, intermediate with the low–glycemic index diet, and least with the very low-carbohydrate diet.
Many people can lose weight for a few months, but most have difficulty maintaining clinically significant weight loss over the long term. According to data from the National Health and Nutrition Examination Survey (1999-2006), only 1 in 6 overweight and obese adults report ever having maintained weight loss of at least 10% for 1 year.1 Among dietary weight-loss trials, in which reporting bias can be eliminated, the long-term success rates may be even lower.2 One explanation for the poor long-term outcome of weight-loss diets relates to behavior, in that the motivation to adhere to restrictive regimens typically diminishes with time. An alternative explanation is that weight loss elicits biological adaptations—specifically a decline in energy expenditure (adaptive thermogenesis) and an increase in hunger—that promote weight regain.
Obesity treatment should emphasize behavioral methods to foster and maintain decreased energy intake. Several recent clinical trials indicate a direct relationship between dietary adherence and weight loss, regardless of dietary treatment group assignment. However, because metabolic pathways vary in energetic efficiency, dietary composition could affect energy expenditure directly by virtue of macronutrient differences or indirectly through hormonal responses to diet that regulate metabolic pathways.
Diets that aim to attenuate the increase in blood glucose levels after eating—specifically, low–glycemic index (emphasizing carbohydrate source) and very low-carbohydrate (focusing on carbohydrate restriction) diets—have been hypothesized to confer such a “metabolic advantage.” Acutely, reducing dietary glycemic load diet may elicit hormonal changes that improve the availability of metabolic fuels in the late postprandial period, and thereby decrease hunger and voluntary food intake. Chronically, a low–glycemic load diet may attenuate the decline in resting energy expenditure (REE) that occurs during weight loss.
We conducted a controlled feeding study to evaluate the effects of 3 weight-loss maintenance diets, which encompass prevailing ranges of macronutrient composition and glycemic load (a low-fat diet, a low–glycemic index diet, and a very low-carbohydrate diet) on energy expenditure, hormones, and components of the metabolic syndrome.
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http://jama.jamanetwork.com/article...ticleid=1199154
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