The effect of body weight changes and endurance training on 24h substrate oxidation.
OBJECTIVE
To investigate the effect of exercise training and dietary macronutrient composition on 24 h substrate oxidation in male, obese subjects.


METHODS
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.


METHODS
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.


METHODS
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.


CONCLUSIONS
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 oxidation.
Pasman
W J
WJ
Maastricht University, Department of Human Biology, The Netherlands. Pasman@voeding.tno.nl
Westerterp
M S
MS
Saris
W H
WH
D000328:Adult; D001835:Body Weight / Q000502:physiology*; D002940:Circadian Rhythm; D004038:Diet, Reducing; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004041:Dietary Fats / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction
D004040:Dietary Carbohydrates; D004041:Dietary Fats