Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man

Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man.

ABSTRACT:   The metabolic balance method was performed on three men to investigate the fate of large excesses of carbohydrate. Glycogen stores, which were first depleted by diet (3 d, 8.35 ± 0.27 MJ [1994 ± 65 kcal] decreasing to 5.70 ± 1.03 MJ [1361 ± 247 kcal], 15% protein, 75% fat, 10% carbohydrate) and exercise, were repleted during 7 d carbohydrate overfeeding (11% protein, 3% fat, and 86% carbohydrate) providing 15.25 1. 10 MJ (3642 ± 263 kcal) on the first day, increasing progressively to 20.64 ± 1 .30 MJ (4930 ± 3 1 1 kcal) on the last day of overfeeding. Glycogen depletion was again accomplished with 2 d of carbohydrate restriction (2.52 MJ/d [602 kcal/d], 85% protein, and 15% fat). Glycogen storage capacity in man is ~15 g/kg body weight and can accommodate a gain of ~500 g before net lipid synthesis contributes to increasing body fat mass. When the glycogen stores are saturated, massive intakes of carbohydrate are disposed of by high carbohydrate-oxidation rates and substantial de novo lipid synthesis (150 g lipid/d using ~475 g CHO/d) without postabsorptive hyperglycemia. 

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