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Substrate utilization during prolonged exercise in obese women differing in body fat distribution
1Department of Kinesiology, University of Colorado at Boulder 80309.
Summary
Obese women with upper or lower body fat patterns utilized similar fuel substrates during prolonged walking. Beta-adrenergic blockade reduced fat utilization equally in both groups, indicating comparable exercise metabolic potential.
Area of Science:
- Exercise Physiology
- Obesity Research
- Metabolic Studies
Background:
- Obesity is characterized by varying fat distribution patterns, influencing metabolic responses.
- Understanding substrate utilization during exercise is crucial for managing obesity and improving metabolic health.
- Beta-adrenergic receptor blockade can affect fuel mobilization during physical activity.
Purpose of the Study:
- To compare substrate utilization during prolonged walking in obese women with distinct upper (UB) and lower (LB) body fat patterns.
- To investigate the effect of beta-adrenergic receptor blockade on substrate utilization in these groups.
- To determine if regional fat distribution influences exercise metabolic responses.
Main Methods:
- Twenty obese women (BMI > or = 30%) were divided into UB (waist-to-hip ratio (WHR) >= 0.85) and LB (WHR <= 0.75) groups.
- Subjects underwent two 60-minute walking trials at 55-60% of maximal aerobic power (VO2max): one with placebo (C) and one with propranolol (PR).
- Open-circuit spirometry measured oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) at 10-minute intervals.
Main Results:
- A significant time-dependent decline in RER was observed in both placebo and propranolol trials, indicating a shift towards fat utilization.
- No significant differences in RER were found between UB and LB groups during either trial.
- Propranolol administration reduced fat utilization by 23% compared to placebo in both groups, with no differential effect based on fat distribution.
Conclusions:
- Obese women with upper and lower body fat patterns exhibit similar substrate utilization patterns during prolonged walking.
- Beta-adrenergic receptor blockade impacts fat utilization similarly across different regional fat distributions in obese women.
- Despite in vitro differences in adipose tissue metabolism, in vivo exercise responses for substrate use are comparable between these groups.