Carbohydrate balance and the regulation of day-to-day food intake in humans

The hypothesis that carbohydrate stores are an important determinant of voluntary food intake was tested by covert dietary manipulation of carbohydrate stores in nine men during 2 d of continuous whole-body calorimetry that provided half-hourly monitoring of energy and fuel balance. On day 1 subjects were fed diets intended to maintain energy balance but containing carbohydrate at either 3% (depletion) or 47% (control) energy. Average carbohydrate balance changed by 153 ± 42 g (x̄ ± SD). Subsequent (day 2) ad libitum food intake from a normal diet of fixed macronutrient composition was identical on the control and depletion protocols: 12.73 ± 2.24 and 12.72 ± 2.01 MJ, respectively. The carbohydrate-depletion protocol caused a suppression of carbohydrate oxidation (174 ± 41 vs 256 ± 39 g, P < 0.001) and a reciprocal elevation in fat oxidation (120 ± 11 vs 89 ± 12 g, P < 0.001). These readjustments in fuel utilization were the primary mechanism for reestablishing carbohydrate balance. This study does not support the hypothesis that the need to maintain specific carbohydrate stores is a determinant of food intake in the short term.