The Effects of Testosterone on Body Composition in Obese Men Are Not Sustained After Cessation of Testosterone Treatment

Background: Testosterone treatment in obese dieting men augments the diet-associated loss of fat mass, but protects against loss of lean mass. We assessed whether body composition changes are maintained following withdrawal of testosterone treatment.

Methods: We conducted a prespecified double-blind randomized placebo-controlled observational follow-up study of a randomized controlled trial (RCT). Participants were men with baseline obesity (body mass index >30 kg/m ) and a repeated total testosterone level <12 nmol/L, previously enrolled in a 56-week testosterone treatment trial combined with a weight loss programme. Main outcome measures were mean adjusted differences (MAD) (95% confidence interval), in body composition between testosterone- and placebo-treated men at the end of the observation period.

Results: Of the 100 randomized men, 82 completed the RCT and 64 the subsequent observational study. Median [IQR] observation time after completion of the RCT was 82 weeks [74; 90] in men previously receiving testosterone (cases) and 81 weeks [67;91] in men previously receiving placebo (controls), P=.51. At the end of the RCT, while losing similar amounts of weight, cases had, compared to controls, lost more fat mass, MAD -2.9 kg (-5.7, -0.2), P=.04, but had lost less lean mass MAD 3.4 kg (1.3, 5.5), P=.002. At the end of the observation period, the former between-group differences in fat mass, MAD -0.8 kg (-3.6, 2.0), P=1.0, in lean mass, MAD -1.3 kg (-3.0, 0.5), P=.39, and in appendicular lean mass, MAD -0.1 kg/m (-0.3, 0.1), P=.45, were no longer apparent. During observation, cases lost more lean mass, MAD -3.7 kg (-5.5, -1.9), P=.0005, and appendicular lean mass, MAD -0.5 kg/m (-0.8, -0.3), P<.0001 compared to controls.

Conclusions: The favourable effects of testosterone on body composition in men subjected to a concomitant weight loss programme were not maintained at 82 weeks after testosterone treatment cessation.