Balance of substrate oxidation during submaximal exercise in lean and obese people

Diabetes Metab. 2001 Sep;27(4 Pt 1):466-74.


Objectives: To compare fat and carbohydrate oxidation at different exercise intensities between overweight and normal-weight subjects, in order to analyze the influence of muscular metabolic abnormalities in obese people on substrate utilization during exercise.

Material and methods: 32 healthy sedentary overweight subjects (Body Mass Index (BMI): 30.8 +/- 0.8 kg/m(2); body fat: 37.4 +/- 1.1%; mean +/- SEM) and 26 controls (BMI: 23 +/- 0.4 kg/m(2); body fat: 22.7 +/- 1.1%) matched for age and sex were examined. The test consisted in four six-min. submaximal steady-state workloads with calculation of substrate oxidation rates and derived quantitative parameters, i.e., crossover point (defined as the power at which carbohydrate-derived energy becomes predominant) and maximal fat oxidation rate point. In addition, the accuracy of the test was analyzed and was found to be satisfactory.

Results: While exercise intensities were similar in both group, fat oxidation rates were significantly lower in overweight group (p<0.05). The crossover and the maximal fat oxidation rate points were significantly lower in overweight subjects than in controls: 33.3 +/- 2 vs 50.1 +/- 3.4% and 30.5 +/- 2.3 vs 44.6 +/- 3.3% of maximal aerobic power, respectively (p<0.001).

Conclusion: Sedentary overweight subjects, compared to controls at the same exercise intensities, exhibited an alteration of the balance of substrate oxidation, reflected by lower rates of fat oxidation and a shift of quantitative parameters to lower intensities. The test appeared to be reliable and could be of interest to advise an individualized exercise prescription in obese people.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Blood Glucose / metabolism
  • Body Height
  • Body Mass Index
  • Body Weight
  • Dietary Carbohydrates
  • Dietary Fats
  • Energy Metabolism
  • Exercise Test
  • Female
  • Humans
  • Insulin / blood
  • Lactates / blood
  • Male
  • Muscle, Skeletal / physiology
  • Muscle, Skeletal / physiopathology
  • Obesity / metabolism
  • Obesity / physiopathology*
  • Oxidation-Reduction
  • Oxygen Consumption*
  • Physical Exertion / physiology*
  • Reference Values
  • Reproducibility of Results
  • Rest


  • Blood Glucose
  • Dietary Carbohydrates
  • Dietary Fats
  • Insulin
  • Lactates