Carbohydrate balance predicts weight and fat gain in adults

The prevention and treatment of obesity is a public health challenge.

We investigated the effects of dietary composition, insulin sensitivity (S(I)), and energy balance on predicted changes in body composition.

In a randomized crossover design study, 39 normal-weight (n = 23), overweight (n = 8), and obese (n = 8) men and women (aged 25-36 y) each followed a 15-d isocaloric high-fat (HF; 50% fat) and high-carbohydrate [HC; 55% carbohydrate (CHO)] diet with a 4-6-wk washout period during the first year. During each treatment, energy balance was measured while the subjects were inactive by using indirect calorimetry on day 15, and S(I) was measured by using a euglycemic clamp study (40 mU . m(-2) . min(-1)) on day 16. Weight and body composition were then measured annually for 4 y. The outcomes for fat mass, percentage body fat, and weight were measured by using a linear 2-stage mixed model.

CHO balance (day 15) and S(I) (day 16) on the HC diet were highly and significantly correlated (r = 0.55, P < 0.001). On the HC diet, the subjects who had a higher positive CHO balance (day 15) gained less fat mass (P < 0.001), percentage body fat (P = 0.006), and weight (P = 0.024) over time. When adjusted for S(I), CHO balance remained a significant predictor of changes in fat mass (P = 0.021) and percentage body fat (P = 0.025).

On a HC diet, the subjects who had a higher positive CHO balance on day 15 while they were inactive gained less fat mass during 4 y, a predictive effect independent of S(I). As suggested in rodents, the capacity to expand the glycogen pool might reduce energy intake and protect against fat and weight gain.