Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance
What is the effect of three diets differing widely in macronutrient composition and glycemic load on energy expenditure following weight loss?
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.
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.
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.
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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