Postprandial sleep and thermogenesis in normal men

Twelve normal male subjects were given low- (16.77 kj/kg) and high- (54.49 kj/kg) calorie liquid carbohydrate lunch meals on 4 days, during which measures of sleep EEG, thermogenesis (heat production), core body temperature, and skin surface temperature were obtained. On 2 days subjects were required to remain awake, and on 2 days sleep was allowed. Both meals were administered in each condition. On the days that subjects were instructed to remain awake, thermogenesis was significantly greater following high-calorie meals than low-calorie meals, and both meal conditions produced levels of thermogenesis that were greater than those observed when sleep was allowed. When given the opportunity, 11 of 12 subjects slept following both low- and high-calorie meals. There was no difference between meal conditions in the total minutes or percent of stages 1, 2, 3 4 , or rapid eye movement (REM) sleep following meals. However, the onset of postprandial sleep episodes was associated with the peak of the postprandial rise in thermogenesis, and the occurrence of sleep was followed by precipitous and statistically significant declines in thermogenesis and core body temperature, as well as increases in skin surface temperature. These data suggest that postprandial sleep is associated with rises in thermogenesis, and that its occurrence decreases postprandial heat production and body temperature.