Postprandial sleep and thermogenesis in normal men.
Level 3 - non-randomized controlled study
Controlled laboratory crossover trial without explicit mention of randomization in the abstract
PubMed 1523250 · doi:10.1016/0031-9384(92)90267-6
What was done
Twelve healthy male subjects completed a 4-day laboratory crossover protocol comparing low-calorie (16.77 kJ/kg) and high-calorie (54.49 kJ/kg) liquid carbohydrate lunches. Each meal type was tested under two conditions: remaining awake or being allowed to sleep. Researchers continuously monitored sleep EEG, thermogenesis (heat production), core body temperature, and skin surface temperature.
What was found
When subjects remained awake, thermogenesis was significantly greater following high-calorie meals than low-calorie meals, and remaining awake produced higher overall thermogenesis than when sleep was permitted. When given the opportunity, 11 of 12 subjects fell asleep after both low- and high-calorie meals, with no significant differences in total sleep duration or sleep architecture (stages 1, 2, 3/4, or REM). Sleep onset coincided with the peak postprandial thermogenic rise. Once sleep occurred, it was followed by statistically significant, precipitous drops in thermogenesis and core body temperature, alongside increases in skin surface temperature. Specific numerical values, variances, and p-values were not provided in the abstract.
Why it matters
This study demonstrates how postprandial sleep actively blunts diet-induced thermogenesis and alters peripheral vs. core thermal regulation, linking meal intake to circadian and sleep-wake physiological dynamics.
Limits
The study had a very small sample size (n = 12) consisting entirely of normal adult men, limiting generalizability to women or individuals with metabolic disorders. The abstract does not report exact numerical effect sizes, variance measures, or whether meal and sleep conditions were randomized.
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