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Effects of obesity on substrate utilization during exercise.
Bret H Goodpaster1, Robert R Wolfe, David E Kelley
1Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Obesity Research
|July 10, 2002
Summary
Obese men utilize more fatty acids and less carbohydrates, particularly muscle glycogen, during moderate exercise compared to lean men. This highlights altered energy metabolism in obesity.
Area of Science:
- Exercise Physiology
- Metabolic Health
- Obesity Research
Background:
- Lipid and carbohydrate oxidation are crucial for energy balance during physical activity.
- Understanding how obesity affects substrate utilization during exercise is vital for metabolic health.
Purpose of the Study:
- To investigate the impact of obesity on lipid and carbohydrate oxidation rates during cycling exercise.
- To compare substrate utilization between obese and lean sedentary men matched for aerobic capacity.
Main Methods:
- Seven obese and seven lean sedentary men performed 60 minutes of cycle exercise at 50% VO2max.
- Substrate oxidation rates were assessed using indirect calorimetry and isotopic tracers.
Main Results:
- Obese men showed increased fatty acid oxidation, primarily from intramuscular sources, compared to lean men.
- Carbohydrate oxidation, specifically muscle glycogen utilization, was significantly lower in obese individuals.
- Systemic glucose disposal rates were comparable between the obese and lean groups.
Conclusions:
- Obesity is associated with a shift towards higher fatty acid oxidation and reduced carbohydrate oxidation during moderate-intensity exercise.
- Muscle glycogen stores appear to be less utilized in obese individuals during exercise.
- These findings suggest altered substrate partitioning in obese individuals during physical activity.