Effect of adipose tissue insulin resistance on substrate utilization during low-intensity exercise: a pilot study in young men.
Shigeharu Numao, Ryota Uchida, Masaki Nakagaichi
Men with higher fat-tissue insulin resistance burned more fat and less carbohydrate during low-intensity cycling, even after accounting for whole-body insulin resistance.
This was a pilot study of 24 healthy young men; the finding needs replication before it should change how you prescribe exercise.
Key findings
1Men with higher adipose tissue insulin resistance had lower carbohydrate oxidation and higher fat oxidation during exercise, and this held after adjusting for whole-body insulin resistance.
2Circulating free fatty acid levels were significantly higher in the high-ATIR group, and FFA levels correlated with substrate oxidation parameters, while blood glucose did not.
3This was a secondary analysis of previously collected data from 24 healthy young men, split into two groups by the median adipose tissue insulin resistance value.
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How it was doneWhat they foundWhat it means for PTs
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What it does not show
All participants were healthy young men aged 20–34, so the finding cannot be assumed to apply to women, older adults, or people with diabetes or obesity. The sample was 24 men split into two groups of 12 by a median, not by a validated clinical threshold for ATIR. The data were re-analysed from a study designed to measure a different outcome (fatty acid binding protein 4), so the exercise protocol and blood sampling were not tailored to this question. Insulin sensitivity was estimated from blood formulas (Adipo-IR, HOMA-IR), not measured with the gold-standard clamp. Only one low intensity (40% of peak) was tested; whether the effect holds at moderate or high intensity is unknown. The study could not tell where the oxidised fuel came from (blood glucose, muscle glycogen, blood fat, or tissue fat).
Declared interests
Funded by a Japan Society for the Promotion of Science grant (22K11552). The authors declare no conflict of interest.
The easy way to misread this
Do not read the significant substrate-oxidation differences as proof that ATIR causes a different fuel-burning pattern in your patients. The unadjusted carbohydrate-oxidation difference was borderline (p = 0.050–0.055), the groups were split by a median in 24 healthy young men at one low intensity, and the data were re-analysed from a study designed for a different question. A single pilot in this narrow population does not establish a clinically actionable rule.
Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →