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Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance
Study Questions:
What is the effect of three diets differing widely in macronutrient composition and glycemic load on energy expenditure following weight loss?
Methods:
A controlled three-way crossover design involving 21 overweight and obese young adults (age 18-40 years with body mass index [BMI] at least 27 kg/m2) was conducted between 2006 and 2010, with recruitment by public advertising. Participants were compensated for their efforts, which included multiple brief hospital stays for data collection. After achieving 10-15% 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. The diet for the weight loss and weight stabilization periods of the run-in phase provided 60% and 100% of estimated energy requirements, respectively. Primary outcome was resting energy expenditure (REE), with secondary outcomes of total energy expenditure (TEE), hormone levels, and metabolic syndrome components.
Results:
Mean age was 30.3 years, BMI 34.4 kg/m2, and 62% were male. During the run-in phase, participants lost a mean of 14.3 kg, corresponding to 13.6% of baseline body weight. Compared with the pre–weight-loss baseline, the decrease in REE was greatest with the low-fat diet (–205 kcal/d), intermediate with the low–glycemic index diet (–166 kcal/d), and least with the very low-carbohydrate diet (−138 kcal/d; overall p = 0.03; p for trend by glycemic load = 0.009). The decrease in TEE showed a similar pattern (−423 kcal/d, −297 kcal/d, and −97 kcal/d, respectively; overall p = 0.003; p for trend by glycemic load < 0.001). Hormone levels and metabolic syndrome components also varied during weight maintenance by diet (leptin, p < 0.001; 24-hour urinary cortisol, p = 0.005; indexes of peripheral [p = 0.02] and hepatic [p = 0.03] insulin sensitivity; high-density lipoprotein [HDL] cholesterol, p < 0.001; non-HDL cholesterol, p < 0.001; triglycerides, p < 0.001; plasminogen activator inhibitor 1, p for trend = 0.04; and C-reactive protein, p for trend = 0.05), but no consistent favorable pattern emerged.
Conclusions:
Among overweight and obese young adults compared with pre–weight loss energy expenditure, isocaloric feeding following 10-15% 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.
Perspective:
Regaining weight after dieting is a frustration that often leads to futility and weight regain. This elegant study suggests the notion that a calorie is a calorie in weight loss is not true. The diet you choose for weight loss can influence weight regaining. After a weight loss of >10% of body weight, when compared to a diet very low in carbs and high-fat, the very low-fat diet had a TEE of about 300 kcal/d more. This would be the equivalent of about an hour of moderate exercise. Energy expenditure on the low–glycemic index diet (e.g., which in this study was 40% fat) is minimally different than the very low-carb high-fat diet, and benefits on the metabolic syndrome parameters are the most favorable.
Keywords: Body Mass Index, Weight Loss, Glycemic Index, Obesity, Diet
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