Metformin doesn't work for longevity—it works for people who eat too much

Hot take: Metformin's anti-aging effects disappear when you control for metabolic health. The TAME trial might confirm what we already know.

Every major study compared diabetics on metformin to diabetics on other drugs or to the general population (40% pre-diabetic). Metabolic optimization looks like anti-aging when baseline is dysfunction.

Bannister et al. (2014) showed metformin-treated diabetics outlived non-diabetic controls—but controls were matched only for age/sex, not metabolic health. Metformin inhibits Complex I, activates AMPK. For nutrient excess, this corrects toward homeostasis. For metabolically healthy people, it's unnecessary drag.

Concerning: Metformin blunts exercise-induced mitochondrial biogenesis, hypertrophy, and VO2max by 15-30% (Konopka et al., Aging Cell 2019). Exercise is the most proven longevity intervention. If metformin undermines it, net effect for healthy individuals could be negative.

Testable prediction: TAME will show benefit only in participants with metabolic dysfunction (HbA1c >5.7%). In metabolically healthy participants, no benefit and possibly reduced exercise capacity.

Is the longevity field's most popular drug a metabolic crutch?