Research

Hormonal

Metformin administration (1,700 mg/day) blunts gains in lean body mass and thigh muscle mass in older adults undergoing progressive resistance training.

If you are over 65 and taking metformin, expect less muscle gain from resistance training compared to someone not taking it. This is likely due to how metformin affects cellular signaling (mTOR/AMPK). Do not stop your medication without medical advice, but adjust your expectations for muscle growth.

StrongRefutesHIGH confidence
Metformin blunts muscle hypertrophy in response to progressive resistance exercise training in older adults... placebo gained more lean body mass (p = .003) and thigh muscle mass (p < .001) than metformin.
R. Grace Walton et al. · Aging Cell · 2019

Why this rating

Randomized, double-blind, placebo-controlled, multicenter trial with a large sample size (N=94) and statistically significant results.

Source

Metformin blunts muscle hypertrophy in response to progressive resistance exercise training in older adults: A randomized, double‐blind, placebo‐controlled, multicenter trial: The MASTERS trial

R. Grace Walton et al. · Aging Cell · 2019

DOI 10.1111/acel.13039

rct · n=94Cited 195×
Read the paper
DOI resolved against Crossref · corpus check 2026-06-10

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