The effects of endurance exercise with and without a reduction of energy intake on fat-free mass and the composition of fat-free mass in obese women.

OBJECTIVE

The objective of this study was to evaluate the effects of endurance exercise on fat-free mass and nitrogen balance, with energy restriction or with energy intake to meet non-exercise needs in obese women.

DESIGN

The study was a 14-week metabolic control study with a 2-week baseline period for dietary stabilization followed by a 12-week period of exercise (E) with or without energy restriction (D), E or D+E.

SETTING

Metabolic research unit of the Western Human Nutrition Research Center.

SUBJECTS

Ten obese women between the ages of 19 and 37 years volunteered as subjects. Body weight ranged from 19% to 41% IBW and body fat was 31-40% of body weight.

INTERVENTION

Women were assigned to either an energy-restricted or energy-'adequate' group so that group means for weight, body fat, FFM, predicted VO2max and RMR were similar. Data were polled for the 2-week baseline period and in 3-week intervals during the intervention period.

RESULTS

The data indicated that E had a slower rate of weight loss and a lower loss of FFM than D+E. Nitrogen balance was more positive in E than D+E. Negative N balance occurred in the D+E group when blood was drawn. There was no decrease in N excretion to compensate for blood losses. N balance for E was positive throughout the study.

CONCLUSION

Changes in FFM, assessed by total body electrical conductivity, were different from the results obtained by classic nitrogen balance. This suggests that losses were due to fluid losses, which were confirmed by deuterium dilution procedures. This study demonstrated that body protein stores remained intact during periods of increased energy expenditure and dietary restriction in obese women.