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.