Long–Term Effects of High‐and Low‐Glycemic Load Energy‐Restricted Diets on Metabolic Adaptation and the Composition of Weight Loss

Abstract

The effects of high glycemic load (HG) and low glycemic load (LG) diets on resting metabolic rate (RMR) and body composition changes in response to caloric restriction (CR) remains controversial. Objective To examine the effects of two CR diets differing primarily in glycemic load on RMR and the % of weight lost as fat and fat free mass (FFM). Methods One year randomized controlled trial of HG and LG diets at 30% CR in 29 healthy overweight adults (mean±SD, age 35±5y; BMI 27.5±1.5 kg/m2). All food was provided for 6 mo, and self‐administered for the next 6 mo. Outcome measures included RMR, fat and FFM. Results There was no significant effect of diet on change in RMR after accounting for the decreases in body fat and FFM, at any time point (p=0.51 at 3 mo, p=0.56 at 6 mo and p=0.85 at 12 mo). In the subgroup of individuals who lost >5% body weight the LG diet group had a significantly higher percentage of weight loss as fat and a significantly lower percentage of weight loss as FFM compared to the HG group (p<0.05). Conclusions This study found no evidence for differential RMR response to weight loss between the HG and LG diets. However, for a given weight loss, the LG diet resulted in greater fat loss and less FFM loss.Support NIH grants NGA‐3U01‐AG20480, K23DK61506, #H150001; USDA 58‐1950‐4‐401