Low Carbohydrate Availability in Energy Balance Alters Bone Turnover and Muscle Proteomic Response With Limited Endocrine Disruption
Study Details
This new study examined the effects of 4 days of low carb availability during energy balance in 8 trained men ๐
Energy availability was maintained at 45 kcal/kg FFM/day in both conditions โก
Carbohydrate intake wasโฆ
๐~1.5 g/kg/day in LOW versus ~7.7 g/kg/day in NORM ๐
โฆwith energy intake matched at ~3,925 kcal/day.
LOW replaced carbohydrate largely with fat, providing ~69% of energy from fat versus 19% in NORM ๐ฅ
Key Findings
๐ Muscle glycogen fell by ~40% during LOW but remained unchanged with normal carb intake
๐ฅ LOW markedly reduced carb oxidation and increased fat oxidation at rest and during exercise
๐ฉธ Circulating ketones, free fatty acids and glycerol also increased, confirming a major shift toward fat metabolism
โ๏ธ Body mass fell ~1.1 kg during LOW, while fat mass remained unchanged, alongside reductions in fat-free mass and total body water
๐ฎโ๐จ RPE was generally higher during exercise with LOW, while exercise efficiency was lower later in the intervention
๐งฌ Insulin, testosterone, T3, leptin, hepcidin and the bone-formation marker P1NP were not significantly altered by low carb availability
๐ IGF-1 showed a different response between conditions, suggesting some suppression of anabolic signalling with LOW
๐ฆด The bone-resorption marker ฮฒ-CTX increased with LOW despite maintained energy availability
๐ฅ Proteins involved in lipid transport and metabolism increased with LOW
๐ Ribosomal, sarcomeric and extracellular-matrix proteins were reduced, suggesting an early anti-anabolic muscle environment
๐งฌ Contrary to the โtrain-lowโ hypothesis, LOW did not produce widespread upregulation of mitochondrial proteins
Conclusion
Low carb availability alone appears insufficient to reproduce the broad endocrine suppression associated with LEA โ๏ธ
However, carb restriction may independently influence bone resorption and muscle anabolic processes even when energy availability is adequate โ ๏ธ
These findings suggest energy deficit may be the dominant driver of systemic endocrine disruption, while carb availability can exert additional tissue-specific effects โ
Reference
https://faseb.onlinelibrary.wiley.com/doi/10.1096/fj.202602531R
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Itโs a pity that this was an exclusive male sample. I wonder if we saw different results in women.