Thermogenesis induced by a high-carbohydrate meal in fasted lean and overweight young men: insulin, body fat, and sympathetic nervous system involvement.
Level 3 - non-randomized controlled study
Non-randomized comparative physiological study comparing two predefined cohorts (lean vs. overweight).
PubMed 12507635 · doi:10.1016/s0899-9007(02)00950-4
What was done
Thirteen healthy, non-smoking, weight-stable young men (6 lean with BMI < 25 kg/m² and 7 overweight with BMI > 27 kg/m²) completed an experimental 7.5-hour fast followed by a high-carbohydrate meal. Indirect calorimetry was used to measure fasting energy expenditure and 4-hour postprandial diet-induced thermogenesis. Serum glucose, serum insulin, heart rate, and urinary catecholamine excretion were also monitored across the fasting and fed periods.
What was found
Overweight men had significantly higher postprandial energy production expressed per kilogram of fat-free mass (kJ/kg FFM) compared to lean controls, although overall diet-induced thermogenesis as a percentage of energy intake did not differ significantly between groups. Diet-induced thermogenesis was positively correlated with absolute body fat, body fat percentage, fat-free mass, and fasting pre-meal serum insulin. Cumulative postprandial energy expenditure directly associated with postprandial insulin response and mean postprandial heart rate. No significant differences were observed in urinary catecholamine excretion between groups at baseline or postprandially. Specific numeric values, effect sizes, and p-values were not provided in the abstract.
Why it matters
These findings suggest that acute carbohydrate-induced thermogenesis is not impaired in young overweight men and that postprandial sympathetic activity and energy expenditure remain tied to insulin and fat mass.
Limits
The sample size was very small (n = 13 total). The cohort was restricted to young men, limiting generalizability to women, older adults, or individuals with metabolic disease. The abstract omits exact numerical measurements, variance, and p-values.
Cited by
- context Hyperglycemia activates the sympathetic nervous system and raises core body temperature.