Evidence check: Insulin in the context of longevity

Insulin is a key metabolic hormone and is closely linked to aging. The insulin/IGF-1 signaling pathway is one of the most conserved longevity pathways in model organisms (worms, flies, mice), where reduced signaling extends lifespan. In humans, the evidence is more nuanced: chronic hyperinsulinemia and insulin resistance are associated with accelerated biological aging and increased risk of age-related diseases. Caloric restriction, intermittent fasting, and drugs like metformin appear to improve insulin sensitivity and are linked to better healthspan. However, direct evidence that lowering insulin in healthy individuals extends human lifespan is lacking. Genetic variants affecting insulin signaling (e.g., in PPARG, LEP) have small effect sizes and are not clinically actionable for longevity. Safety note: manipulating insulin levels without medical supervision can cause hypoglycemia and other risks. Overall, the evidence is moderate for a mechanistic link, but insufficient for specific longevity recommendations based on insulin alone.