Abstract P125: Aerobic Exercise Training Reduces Postprandial Thermogenesis in Older Women

Abstract

Introduction: Thermic effect of food is a component of total daily energy expenditure (TDEE). Some literature suggests lower postprandial rise in energy expenditure predicts future weight gain. It is also known that other components of TDEE, resting metabolic rate (RMR) and free-living physical activity energy expenditure, are prone to change in response to exercise training. However, most studies estimate thermic effect of food as a proportion of TDEE and thus have not evaluated whether changes in postprandial thermogenesis occur in response to exercise training. The objective of this study was to determine whether postprandial thermogenesis changed after completing aerobic exercise training in older women. Hypothesis: We hypothesize that the postprandial thermogenesis decreases in sedentary older women who complete 16-week aerobic exercise training. Methods: Sedentary older women (n = 47; age = 65.1 ± 4.3 years) completed 16-week moderate-intensity aerobic exercise training. RMR and 5-hour postprandial thermogenesis following ingesting the same meal, before and at the end of training, was measured via indirect calorimetry. The meal consisted of approximately 40% of each woman’s RMR at baseline. Postprandial thermogenesis was calculated as area under the curve. TDEE was also measured using doubly labelled water before and at the end of training. Results: After exercise training, RMR and TDEE did not change (p > 0.05 for both). Total postprandial thermogenesis (from 287 ±36 to 276 ± 40 kcal for 5 hours, p = 0.008) and postprandial thermogenesis in the first hour (from 69.9±8.7 to 66.3±8.1 kcal, p = 0.05) decreased significantly. The ratios of total and first-hour postprandial thermogenesis to TDEE also decreased (p = 0.026 and 0.013, respectively). Conclusion: Postprandial thermogenesis following the same meal reduced after aerobic training in older women. This adaptive change may contribute to an individual’s ability to defend the body’s energy store.