What is IGF-1?
Insulin-like growth factor 1
IGF-1 is a hormone, a chemical messenger, that tells cells throughout your body to grow and divide.
Think of IGF-1 as an accelerator pedal for growth. Pressing it hard is great while you're a growing child. In adulthood, keeping the pedal pressed all the time may wear the engine faster.
Why it matters for aging
IGF-1 is made mostly by the liver, in response to growth hormone and to the protein you eat. It peaks during puberty and slowly declines with age.
Fasting and very low-protein diets lower IGF-1, which is one reason the fasting mimicking diet focuses on keeping protein low for a few days. In a randomized trial, three monthly cycles of that diet lowered IGF-1 along with weight and blood pressure.
A common myth
Higher IGF-1 always means better health and more youthfulness.
IGF-1 is essential for growth and muscle, and very low levels in older adults can be a problem too. But in animals, lower growth signaling is linked to longer life, and very high IGF-1 in adults has been linked to some age-related diseases. Balance matters.
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Updated Nov 9, 2026 · All terms