Testosterone shifts about two kilos of fat and muscle
Over three years in men past 65 it cut 3.0 kg of fat and added 1.9 kg of lean mass against placebo. Pooled trials in men over 40 put the lean gain at 2.54 kg.
What the study found
The body-composition gain is real and it is about two kilos
Three years in men over 65 cut fat mass 3.0 kg and added 1.9 kg of lean mass against placebo. Eleven pooled trials in men over 40 put the lean gain at 2.54 kg, and a pooling of 16 more found lean mass and hip bone density up at six months. It is the outcome these trials agree on.
The caveat · Many men were not low to start
Most of these trials enrolled men by age rather than by a low testosterone reading, so many participants were not deficient. A gain in lean mass is not by itself a gain in anything a man would notice. In the 16-trial pooling, whose men averaged 77 years old, no musculoskeletal difference from placebo was left by 12 months, which could mean the effect fades or only that fewer trials reported that far out.