Carbohydrate and Fat Oxidation in Muscle Assessed with Exercise Calorimetry in 6465 Subjects
Jean-Frédéric Brun1, Emmanuel Varlet1, Justine Myzia1
1Unité d'Explorations Métaboliques et Musculaires (UEMM), Département de Physiologie Clinique, Hôpital Lapeyronie-CHU de Montpellier, Université de Montpellier, 34295 Montpellier, France.
Metabolites
|February 26, 2026
Summary
This study reveals that body composition, age, and sex significantly influence how the body burns fat and carbohydrates during exercise. Leaner individuals prioritize fat oxidation, while those with higher adiposity rely more on carbohydrate oxidation.
Area of Science:
- Exercise physiology and metabolism.
- Nutritional biochemistry and metabolic flexibility.
Background:
- Lipid and carbohydrate (CHO) oxidation rates during exercise are crucial for energy metabolism.
- Factors influencing CHO oxidation are less understood compared to lipid oxidation.
- Maximal lipid oxidation (LIPOXmax) is well-studied, especially for exercise prescription in obesity.
Purpose of the Study:
- To investigate determinants of maximal lipid oxidation (LIPOXmax).
- To characterize factors influencing carbohydrate oxidation during exercise.
- To analyze these factors within a large cohort.
Main Methods:
- Exercise calorimetry in 6465 individuals (4561 women, 1904 men).
- Derived LIPOXmax (intensity of maximal fat oxidation).
- Derived carbohydrate cost of the watt (CCW) (CHO oxidation relative to power output).
Main Results:
- LIPOXmax positively associated with lean/muscle mass, negatively with fat mass/age.
- Women showed higher relative lipid oxidation and higher CCW compared to men.
- CCW positively correlated with BMI, fat mass, age; negatively with muscle mass, LIPOXmax.
Conclusions:
- Higher adiposity correlates with greater reliance on CHO oxidation; leaner individuals favor lipid oxidation.
- Body composition, age, and sex are major determinants of substrate utilization during exercise.
- Findings offer insights into metabolic flexibility relevant for obesity and hypoglycemia risk.
Keywords:
FATmaxLIPOXmaxcalorimetrycarbohydrate cost of the watt (CCW)carbohydrate oxidationfatfat metabolismindirect calorimetrylipid metabolismlipid oxidationmaximal fat oxidation (MFO)peak fat oxidationskeletal musclesubstrate oxidationtrainingMore Related Videos
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