Research

Hormonal

In healthy men, estrogen deficiency (caused by aromatase inhibition) is the primary driver of increased body fat, whereas testosterone deficiency is the primary driver of decreased lean mass, muscle size, and strength.

If you are a man experiencing fat gain or loss of muscle/strength, do not assume it is solely due to low testosterone. This study shows that low estrogen (estradiol) is a primary driver of fat gain, while low testosterone drives muscle loss. Treatment strategies should consider both hormones, not just testosterone replacement.

StrongSupportsVERY_HIGH confidence
Androgen deficiency accounted for decreases in lean mass, muscle size, and strength; estrogen deficiency primarily accounted for increases in body fat; and both contributed to the decline in sexual function.
Joel S. Finkelstein et al. · New England Journal of Medicine · 2013

Why this rating

Randomized, double-blind, placebo-controlled trial with rigorous hormonal manipulation (goserelin + testosterone +/- anastrozole) in healthy men.

Source

Gonadal Steroids and Body Composition, Strength, and Sexual Function in Men

Joel S. Finkelstein et al. · New England Journal of Medicine · 2013

DOI 10.1056/nejmoa1206168

rct · n=400Cited 775×
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DOI resolved against Crossref · corpus check 2026-06-10

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