Lipid oxidation in overweight men after exercise and food intake

Fat oxidation (FO) is optimized during low- to moderate-intensity exercise in lean and obese subjects, whereas high-intensity exercise induces preferential FO during the recovery period. After food intake during the postexercise period, it is unknown if FO differs according to the intensity exercise in overweight subjects. Fat oxidation was thus evaluated in overweight men after low- and high-intensity exercise during the recovery period before and after food intake as well as during a control session. Ten healthy, sedentary, overweight men (age, 27.9 ± 5.6 years; body mass index, 27.8 ± 1.3 kg m−2; maximal oxygen consumption, 37 ± 3.9 mL min−1 kg−1) exercised on a cycloergometer (energy expenditure = 300 kcal) at 35% (E35) or 70% (E70) maximal oxygen consumption or rested (Cont). The subjects were fed 30 minutes after the exercise with 300 kcal (1256 kJ) more energy in the exercise sessions than in the Cont session. Respiratory quotient and FO were calculated by indirect calorimetry. Blood samples were analyzed to measure plasma glycerol, nonesterified fatty acid, glucose, and insulin. During exercise, mean respiratory quotient was lower (P < .05) and FO was higher (P < .01) in the E35 than in the E70 session (FO [in mg min−1]: E35 = 290 ± 12, E70 = 256 ± 38, and Cont = 131 ± 7). Conversely, FO was higher in the E70 than in both the E35 session and the Cont session during the immediate recovery as well as during the postprandial recovery period (P = .005 for all; FO from the end of the exercise to the end of the session [in grams]: E70 = 45.7 ± 8.9, E35 = 38.2 ± 6.8, and Cont = 36.0 ± 4.3). Blood parameters did not differ between the 3 sessions but changed according to the absorption of the nutrients. In overweight subjects, high-intensity exercise increased FO during the postexercise period even after food intake compared with the low-intensity exercise and the control session.