Lower excess postexercise oxygen consumption and altered growth hormone and cortisol responses to exercise in obese men.
BACKGROUND
Obesity is associated with altered patterns of substrate utilization at rest and during exercise.


OBJECTIVE
The relationship between obesity and fat oxidation during recovery from exercise was examined.


OBJECTIVE
The postexercise shift toward fat oxidation is blunted in the obese state, reflected by higher respiratory exchange ratio (RER), blunted GH, and increased cortisol values compared with lean controls.


METHODS
Each subject completed two 160-min protocols (baseline and exercise). During baseline, subjects rested for 160 min; during exercise, they completed 30 min of cycling at ventilatory threshold, followed by 130 min of rest.


METHODS
This study was performed at the University of Alberta.


METHODS
Healthy untrained (maximal oxygen consumption, <45 ml/kg.min or <3.35 liter/min) lean (<16% body fat; n = 6) and obese (>25% body fat; n = 7) men, aged 30-39 yr, were studied.


METHODS
RER, GH, cortisol, oxygen consumption, heart rate, tympanic temperature, and lactate were obtained during both protocols at matched time intervals and analyzed by repeated measures ANOVA.


RESULTS
During baseline, there were no differences detected between lean and obese groups for any of the measured variables. In contrast, during exercise, peak GH levels were blunted (P < 0.05) and cortisol levels were elevated (P < 0.05) in the obese compared with the lean subjects, but RER values were similar in the two groups. The differences in GH and cortisol persisted during the postexercise period accompanied by higher RER values (P < 0.05) and reduced total oxygen consumption (P < 0.05) in the obese group.


CONCLUSIONS
These findings indicate that exercise-induced fat oxidation is diminished in obese men.
Wong
Tina
T
Faculty of Physical Education and Recreation, University of Alberta, E-424 Van Vliet Center, Edmonton, Alberta, Canada T6G 2H9.
Harber
Vicki
V
D000328:Adult; D001831:Body Temperature / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009765:Obesity / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology*; D012119:Respiration
D019382:Human Growth Hormone; D019344:Lactic Acid; D006854:Hydrocortisone