The effect of body weight changes and endurance training on 24h substrate oxidation

The effect of body weight changes and endurance training on 24h substrate oxidation.Pasman WJ, Westerterp MS, Saris WH.Maastricht University, Department of Human Biology, The Netherlands. Pasman@voeding.tno.nlOBJECTIVE: To investigate the effect of exercise training and dietary macronutrient composition on 24 h substrate oxidation in male, obese subjects. DESIGN: A 16 month exercise intervention study was executed, including a weight loss period with a very low energy diet (VLED) for 2 months at the start of the study. SUBJECTS: Twelve male, obese subjects (age 36.3+/-5.1 y; body weight 94.6+/-13.9 kg; body mass index, BMI 30.8+/-3.0 kg/m2) and in an additional study 15 lean, well-trained subjects (age 36.2+/-7.2 y; body weight 72.2+/-5.9 kg; BMI 22.3+/-1.7 kg/m2) participated. MEASUREMENTS: Substrate oxidation was measured during a standardized 36 h stay in the respiration chamber at the start of the study (0 months), and at 4, 10 and 16 months. In the respiration chamber subjects were randomly assigned to a high-fat (Hi.F) diet (60% of energy (En%) fat) or a reduced-fat (Red.F) diet (30 En% fat). The well-trained group was measured once in the respiration chamber for 36 h according to the same protocol. RESULTS: At any time point, independent of the diet consumed, the 24 h carbohydrate (CHO) balances in the chamber were mostly negative (means ranging from +31 to -98 g/d) and the fat balances mostly positive (means ranging from -26 to +38 g/d) for the obese a well as for the lean, well-trained group. For both diets an increased shortage of 70 g of CHO was found at 16 months compared with 4 months, and an increase in fat balance of 33 g during the same time period in the obese subjects, indicating that CHO oxidation had increased with 12 months endurance training. In the well-trained group the 24h CHO balance was even more negative for both types of diet (-103 to -185 g/d for the Red.F and Hi.F diet, respectively) under similar conditions compared with the trained obese group. CONCLUSION: The changes in 24 h substrate utilization in the obese, as well as in the well-trained group, suggest that endurance training increased the reliance on carbohydrate oxidation and therefore did not increase 24 fat oxidatio