Research

Hormonal

Insulin reduces whole-body protein breakdown (proteolysis) in a dose-dependent manner in healthy postabsorptive men, primarily by suppressing the release of leucine from body protein stores.

In the fasted state, your body's insulin levels act as a switch to stop muscle breakdown. Higher insulin levels (within physiological ranges) more effectively suppress protein breakdown. This is why maintaining some level of insulin (e.g., via protein intake) can help preserve muscle mass during fasting or caloric deficits.

GoodSupportsHIGH confidence
These data indicate the presence of insulin-dependent suppression of leucine entry into the plasma compartment in man secondary to a reduction in proteolysis and the stimulation of alanine synthesis during euglycemic hyperinsulinemia.
Naomi K. Fukagawa et al. · Journal of Clinical Investigation · 1985

Why this rating

Controlled clinical trial with stable isotope tracers in healthy young men, though small sample size (n=5).

Source

Insulin-mediated reduction of whole body protein breakdown. Dose-response effects on leucine metabolism in postabsorptive men.

Naomi K. Fukagawa et al. · Journal of Clinical Investigation · 1985

DOI 10.1172/jci112240

mechanism_only · n=5Cited 373×
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DOI resolved against Crossref · corpus check 2026-06-10

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