The singular and combined effects of exercise and meal ingestion on caloric expenditure
Willms, Wendy L.
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The influence of exercise on the thermic effect of food has been examined in untrained (V̇O₂max [40% ml·kg·min⁻¹]), nonobese (body fat <30%) female subjects. Subjects participated in four separate testing sessions which consisted of postabsorptive resting metabolic rate (RMR) (NENF); postabsorptive RMR followed by measurement of postprandial RMR (Meal = 920 kcal; 60% carbohydrate, 25% fat, 15% protein) (NEF); postabsorptive exercise MR (58% V̇O₂max for 30 min) (ENF); and postabsorptive exercise MR followed by measurement of postprandial MR (EF). Metabolic rate, expressed as respiratory exchange ratio (RER) oxygen (V̇O₂) uptake and later converted into caloric expenditure (kcal), was measured continuously for intervals of 15 min of rest, 30 min of exercise/no exercise, and 60 min of recovery. No significant differences were observed in metabolic data across all four resting conditions (p̲>0.01). Exercise caused a consistent enhancement of metabolic rate in both ENF and EF conditions. During recovery there were no significant changes in metabolic data caused by exercise alone (ENF). The thermic effect of food (TEF) averaged a 15-26% increase in V̇O₂ consumption (.294 ± .049) and kcal expenditure (1.47 ± .24) during recovery. There was a significant but similar elevation of mean V̇O₂ uptake during recovery by 14.96% in the NEF (.29 ± .049) and 13.70% in the EF (.292 ± .048) protocols (p̲<0.01). The parallel elevation in O₂ consumption and kcal expenditure in the two food protocols (NEF, EF) indicated no additive effect of food in combination with exercise. Although meal ingestion caused a thermic effect of food, metabolic data did not differ during recovery when exercise was added; therefore, exercise did not enhance TEF. However, the EF protocol yielded a significantly greater overall caloric expenditure (304.40), as compared to the other protocols (NENF = 121.28, NEF = 142.13, ENF = 291.43), signifying the added benefit of exercise in weight reduction.