Research
Macro partitioning
Endurance training increases maximal fat oxidation (MFO) and shifts the intensity at which MFO occurs to higher workloads, primarily through increased intramuscular triglyceride (IMTG) utilization and mitochondrial density.
If you train for endurance, your body becomes more efficient at burning fat. This is due to increased mitochondrial density and greater storage of fat within muscles (IMTG). This adaptation allows you to burn more fat at higher intensities than an untrained person.
GoodSupportsHIGH confidence
Endurance-trained subjects displayed a higher maximal fat oxidation rate, a greater proportion of type I muscle fibers and higher intramuscular lipids content compared to untrained individuals.
Why this rating
Supported by multiple studies cited in the review showing consistent improvements in MFO and mitochondrial density in trained vs. untrained subjects.
Source
The Regulation of Fat Metabolism during Aerobic Exercise
Antonella Muscella et al. · Biomolecules · 2020
DOI 10.3390/biom10121699
narrative_reviewCited 217×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Fat oxidation during aerobic exercise is maximized at moderate intensities (approximately 60-65% VO2max) and decreases significantly at higher intensities (>75% VO2max) due to the Randle cycle and reduced plasma fatty acid availability.Good
- High-intensity exercise stimulates intramuscular triglyceride (IMTG) lipolysis, but the released fatty acids are not immediately oxidized; instead, they are released into the plasma and utilized during recovery.Moderate
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