The Effects of Exercise Training and Dietary Supplementation on Fat Metabolism and Body Composition in Obese Women

Reduced energy expenditure and impaired fat oxidation are critical factors associated with obesity. Although much is known about the effects of exercise training on fat metabolism in normal weight, healthy women, considerably less is known about the potential benefits of exercise on fat metabolism in obesity. PURPOSE: 1) To determine the effects of aerobic exercise on fat metabolism and body composition in previously sedentary obese women. 2) To examine whether a dietary supplement purported to increase metabolism will elicit further improvements in fat metabolism and body composition when combined with exercise. METHODS: 15 Obese (BMI > 30 kg/m2) premenopausal women aged 36 ± 7 years completed a 16- week intervention consisting of moderate exercise. Women were randomized into either a dietary supplement group or placebo; all participated in the exercise training intervention. Pre and post intervention, all subjects underwent a DXA, graded exercise test, and indirect calorimetry to measure energy expenditure and fat oxidation at rest and during exercise (treadmill walking at 55% VO2 max). RESULTS: VO2 max improved on average by 11% from 50.9 ± 8.2 to 56.1 ± 8.1 ml/kgFFM/min; (p<0.01). There was a significant weight loss overall (85.5 ± 9.7 to 83.2 ± 10.1kg; p< 0.05) but there was no significant difference between intervention groups. However, the analysis revealed a significant weight loss in the supplement group (89.9 ± 10.9 to 87.4 ± 12.0 kg; p<0.05), while the Placebo group did not quite reach significant differences (80.5 ± 5.0 ± to 78.3 ± 5.9, p=0.06). The amount of weekly structured exercise (kcal per week) was strongly associated with greater reductions in waist circumference (R2=0.77; P<0.05). There was an exercise-training induced increased rate of fat oxidation during 60 minutes of sub-maximal exercise (0.30 ± 0.06 to 0.34 ± 0.12 g/min; p<0.05). There was, however, no change in resting metabolic rate (RMR) or resting fat oxidation. CONCLUSION: Exercise training increases the reliance on fatty acids for energy during physical activity in obese women. Exercise training also improved body composition. These improvements were not affected by the dietary supplement.