Effects of aerobic exercise on energy expenditure and nitrogen balance during very low calorie dieting.

Aerobic exercise in addition to severe caloric restriction was studied for its effects on resting energy expenditure (REE), weight loss, and lean tissue preservation in adult women. A formula diet providing 1.5 g protein and 0.5 g carbohydrate (CHO) per kilogram of ideal body weight daily (mean intake 720 kcal/d) was given to 12 overweight inpatients for 4 to 5 weeks. Six subjects remained sedentary (group 1), while the other six subjects (group 2) performed supervised endurance exercise (a total of 27 hours at 50% of maximal oxygen uptake (VO2max) over 4 weeks). Lean tissue preservation was excellent in both groups and was unaffected by the group 2 exercise regimen. Weight loss over 4 weeks in the two groups did not differ (group 1, 6.9 +/- 0.7 kg; group 2, 6.5 +/- 0.7 kg). The VO2max was not increased after 4 weeks of exercise compared with controls. The resting oxygen consumption (rVO2) of both groups declined 10% (P less than .001) in the first seven days of dieting. Thereafter the rVO2 in group 1 remained stable, but a further 17% reduction occurred in group 2 (P less than .03) by the third week of exercise. The free triiodothyronine (fT3) concentration also fell more in group 2 (P less than .05), suggesting a relationship between fT3 and energy expenditure during severe caloric restriction. The ergometer exercise for up to two hours daily was well tolerated. The absence of either a training effect or accelerated weight loss in group 2 may be due to the limited duration (4 weeks) or intensity of the exercise.(ABSTRACT TRUNCATED AT 250 WORDS)