Diet-induced thermogenesis does not differ after ingestion of an isoenergetic meal, whereas early-phase thermogenesis differed between athletes and non-athletes

PURPOSE: Habitual exercise is considered to be one of the factors that influence diet-induced thermogenesis (DIT). Still, whether DIT differs between athletes and non-athletes remains unclear due to the effects of test meal's volume and nutritional composition. This study aimed to reveal whether the DIT of athletes differs from that of non-athletes after ingesting an isoenergetic meal with a typical nutritional composition in Japan. METHODS: Twenty-six highly trained male athletes and 11 male non-athletes participated in this study. Measurements for determining DIT consisted of measurements of resting energy expenditure (REE) and postprandial energy expenditure by indirect calorimetry using the Douglas bag technique. After measuring REE, participants ingested a liquid test meal (600 kcal, 15% energy from protein, 25% energy from fat, and 60% energy from carbohydrates). Postprandial energy expenditure was measured up to 180 min. Thermogenesis at each postprandial time point was calculated by subtracting REE from postprandial energy expenditure. DIT over the 200-min period was determined from the area under the curve. RESULTS: The results showed no significant differences in DIT and the percentage of DIT to test meal energy over the 200-min period. The thermogenesis at 20, 40, and 60 min after ingestion of the test meal were 27.5%, 25.8%, and 27.0% greater in athletes than in non-athletes, respectively. CONCLUSION: There were no differences in DIT between athletes and non-athletes, but thermogenesis was significantly higher in athletes during the first 60 min of the DIT measurement, indicating differences in digestion, absorption, or storage of nutrients.