Post Exercise Carbohydrate And Fat Oxidation Rates In Women With Different Levels Of Body Fat

Abstract

PURPOSE: Substrate oxidation during and after exercise may be affected by the level of body fat. We investigated the effects of prior exercise on post-exercise carbohydrate (CHO) and fat (FAT) oxidation rates in women of high (>25%, HF) and low (<25%, LF) body fat percentage. METHODS: 14 healthy, physically active young (18-23 y) females were categorized by body composition into a high fat >25% (HF, n=8) or low fat <25% (LF, n=6) group. Air displacement plethysmography was used to determine percent body fat (% fat), fat-free mass (FFM), and fat mass (FM), and a graded exercise test was used to determine maximal aerobic power (VO2max). HF women were 30.9±3.7% fat; LF women were 21.6±2.6% fat. Following a 10 h fast, subjects completed 2 treatment sessions (30 min and 60 min duration) of treadmill exercise at 55% of VO2max. For 2 h post-exercise, expired gases were analyzed to determine FAT and CHO oxidation rates, which were normalized to mg/kg FFM/min. A group x treatment x time ANOVA was used to determine significant differences with p<0.05. RESULTS: There was no significant difference between groups for VO2max (HF 63.6±11.8 ml/kg FFM/min and LF 62.2±5.9 ml/kg FFM/min). There were no significant differences between groups or within the 2 h post-exercise period following the 30 min session. A significant group effect was observed following the 60 min exercise session with HF women displaying lower CHO and higher FAT oxidation rates (mg/kg FFM/min) during the 2 h post-exercise period.Table: No caption provided.CONCLUSIONS: In women of similar fitness levels, the percentage of body fat may play a role in determining post-exercise substrate oxidation rates during exercise of longer duration (e.g. 60 min vs 30 min).