Energy Metabolism In Overweight Women

Abstract

1017 PURPOSE: To compare fat metabolism in two groups of women; trained normal weight (TNW) & untrained over weight (UOW) women. METHODS: All subjects performed a graded exercise test to determine maximal oxygen consumption (VO2 max). Resting metabolic rate was measured via indirect calorimetry. Rate of fat oxidation was determined during a 1 hour moderate intensity (55% of VO2 max) treadmill exercise test estimated from oxygen uptake (VO2) and carbon dioxide production (VCO2). RESULTS: TNW (n = 10) were more physically fit than UOW (n = 10) evidenced by their higher VO2 max (45.6 ± 1.5 vs. 28.7 ± 1.5 ml/kg/min; P < 0.0001). The UOW had a significantly higher percent body fat (44.5% ± 1.4 vs. 24.7% ± 1.3; P <0.0001) and fat mass (37.0 ± 1.9 vs. 14.8 ± 1.9 kg; P < 0.0001) compared to the TNW. There were no differences between TNW and UOW, respectively in resting metabolic rate (1349 ± 46 vs. 1436 ± 46 kcal/24 hrs; p > 0.199), oxidation of fat during resting conditions (0.065 ± 0.01 vs. 0.074 ± 0.01 g/min; p > 0.3812) or during one hour of moderate (55% of VO2max) intensity treadmill exercise (0.55 ± 0.03 vs. 0.46 ± 0.06 g/min; p > 0.06). During exercise, both groups significantly increased their fat oxidation over the course of 60 minutes of exercise (33% ± 7.9 in TNW and 24% ± 7.9 in UOW; p > 0.4461). CONCLUSION: Overweight to mildly obese sedentary women are not impaired in their ability to oxidize fat during moderate physical activity. To the contrary, these women have a similar ability as normal weight, physically fit women in augmenting their rates of fat oxidation with increasing duration of exercise. Taken together, this study suggests that regular moderate intensity exercise of sufficient duration in overweight women may confer beneficial effects on fat metabolism and overall energy balance.