An US randomized feeding trial concluded that lowering dietary carbohydrate increased energy expenditure during weight loss maintenance. The study included 164 adults aged 18-65 years with a body mass index of 25 or more from August 2014 to May 2017. After 12% (within 2%) weight loss on a run-in diet, participants were randomly assigned to one of three test diets according to carbohydrate content (high, 60%, n=54; moderate, 40%, n=53; or low, 20%, n=57) for 20 weeks. Test diets were controlled for protein and were energy adjusted to maintain weight loss within 2 kg. Energy expenditure was measured with doubly labeled water. Total energy expenditure differed by diet in the intention-to-treat analysis (n=162), with a linear trend of 52 kcal/d for every 10% decrease in the contribution of carbohydrate to total energy intake (1 kcal=4.18 kJ). Change in total energy expenditure was 91 kcal/d greater in participants assigned to the moderate carbohydrate diet and 209 kcal/d greater in those assigned to the low carbohydrate diet compared with the high carbohydrate diet. In the per protocol analysis (n=120), the respective differences were 131 kcal/d and 278 kcal/d. Among participants in the highest third of pre-weight loss insulin secretion, the difference between the low and high carbohydrate diet was 308 kcal/d in the intention-to-treat analysis and 478 kcal/d in the per protocol analysis. Ghrelin was significantly lower in participants assigned to the low carbohydrate diet compared with those assigned to the high carbohydrate diet (both analyses). Leptin was also significantly lower in participants assigned to the low carbohydrate diet (per protocol). The study shows that dietary quality can affect energy expenditure independently and suggests that this metabolic effect may have implications in obesity treatment. Source: https://www.bmj.com/
