Research

Energy balance

Restoring adequate dietary energy intake is the primary driver for increasing serum somatomedin-C (IGF-1) levels after fasting, whereas protein intake alone is insufficient to sustain this increase without sufficient calories.

If you are recovering from a period of fasting, crash dieting, or low-calorie intake, simply eating more protein will not immediately restore your body's natural growth hormone signaling (IGF-1). You must first restore your total caloric intake to normal levels. Energy availability is the primary switch that allows your body to resume normal production of growth factors, regardless of protein intake.

GoodSupportsHIGH confidence
An adequate supply of energy appears to be essential for the rise in somatomedin-C after fasting. This is suggested by the finding that, compared with the rise noted in subjects refed a low protein-adequate energy diet... feeding the diet in which energy was restricted... caused a further decline.
W L Isley et al. · Journal of Clinical Investigation · 1983

Why this rating

Controlled clinical trial with rigorous dietary manipulation and specific biochemical assays, though small sample size (n=5).

Source

Dietary components that regulate serum somatomedin-C concentrations in humans.

W L Isley et al. · Journal of Clinical Investigation · 1983

DOI 10.1172/jci110757

crossover · n=5Cited 436×
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DOI resolved against Crossref · corpus check 2026-06-10

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