Location: Children's Nutrition Research CenterTitle: Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: Randomized trial
|EBBELING, CARA - Boston Children'S Hospital|
|FELDMAN, HENRY - Harvard Medical School|
|KLEIN, GLORIA - Boston Children'S Hospital|
|WONG, JULIA - Boston Children'S Hospital|
|BIELAK, LISA - Boston Children'S Hospital|
|STELTZ, SARAH - Boston Children'S Hospital|
|LUOTO, PATRICIA - Framingham State College|
|WOLFE, ROBERT - University Of Arkansas|
|WONG, WILLIAM - Children'S Nutrition Research Center (CNRC)|
|LUDWIG, DAVID - Boston Children'S Hospital|
Submitted to: British Medical Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2018
Publication Date: 11/14/2018
Citation: Ebbeling, C.B., Feldman, H.A., Klein, G.L., Wong, J.M., Bielak, L., Steltz, S.K., Luoto, P.K., Wolfe, R.R., Wong, W.W., Ludwig, D.S. 2018. Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: Randomized trial. British Medical Journal. 363:k4583. https://doi.org/10.1136/bmj.k4583.
Interpretive Summary: Diets with high amount of sugars, pasta, and grain products are linked to increase in unhealthy body weight. Weight loss by diet might be effective but keeping the amount of weight loss over time is difficult. Diets with low content of sugars, pasta, and grain products might increase calories used by the body and depress appetite and therefore might prevent weight regain. To test this idea, we enrolled 164 adults between 18 and 65 years of age into a study. After these adults lost about 12% of body weight on a control diet, they were divided into three groups. The first group of 54 adults stayed on a diet made up with 60% of sugars, pasta, and grain product for 20 weeks. The second group of 53 adults stayed on a diet made up with 40% of sugars, pasta, and grain products, also for 20 weeks. The third group of 57 adults were fed a diet made up with 20% of sugars, pasta, and grain products, again for 20 weeks. All three diets contained the same amount of protein while making changes on the calorie of the diets to keep the body weight within 4.5 lb over the 20-week period. At the end of the 20-week feeding study, the total amount of energy used by the body was the highest among the adults who were fed the diet with the lowest amount (20%) of sugars, pasta, and grain products. These adults also had the lowest amount of appetite stimulating hormone in their blood. Adults fed the diet with the highest amount (60%) of sugars, pasta, and grain products used the least amount of energy. Therefore, our study showed that diet with low amount of sugars, pasta, and grain products might help to prevent weight regain in a weight loss program.
Technical Abstract: To determine the effects of diets varying in carbohydrate to fat ratio on total energy expenditure. Randomized trial. Multicenter collaboration at US two sites, August 2014 to May 2017. 164 adults aged 18-65 years with a body mass index of 25 or more. 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. To test for effect modification predicted by the carbohydrate-insulin model, the sample was divided into thirds of pre-weight loss insulin secretion (insulin concentration 30 minutes after oral glucose). The primary outcome was total energy expenditure, measured with doubly labeled water, by intention to-treat analysis. Per protocol analysis, included participants who maintained target weight loss, potentially providing a more precise effect estimate. Secondary outcomes were resting energy expenditure, measures of physical activity, and levels of the metabolic hormones leptin and ghrelin. Total energy expenditure differed by diet in the intention-to-treat analysis (n=162, P=0.002), with a linear trend of 52 kcal/d (95% confidence interval 23 to 82) for every 10% decrease in the contribution of carbohydrate to total energy intake (1 kcal=4.18 kJ=0.00418 MJ). Change in total energy expenditure was 91 kcal/d (95% confidence interval -29 to 210) greater in participants assigned to the moderate carbohydrate diet and 209 kcal/d (91 to 326) greater in those assigned to the low carbohydrate diet compared with the high carbohydrate diet. In the per protocol analysis (n=120, P<0.001), the respective differences were 131 kcal/d (-6 to 267) and 278 kcal/d (144 to 411). 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 (P<0.004). 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). Consistent with the carbohydrate-insulin model, lowering dietary carbohydrate increased energy expenditure during weight loss maintenance. This metabolic effect may improve the success of obesity treatment, especially among those with high insulin secretion.