The effects of testosterone on body composition in obese men are not sustained after cessation of testosterone treatment

BackgroundTestosterone 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. MethodsWe 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 styled-content style=text-decoration:underline styled-content 30kg/m(2)) and a repeated total testosterone level styled-content style=text-decoration:underline styled-content 12nmol/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. ResultsOf the 100 randomized men, 82 completed the RCT and 64 the subsequent observational study. Median [IQR] observation time after completion of the RCT was 82weeks [74; 90] in men previously receiving testosterone (cases) and 81weeks [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 -2.9kg (-5.7, -0.2), P=.04, but had lost less lean mass MAD 3.4kg (1.3, 5.5), P=.002. At the end of the observation period, the former between-group differences in fat mass, MAD -0.8kg (-3.6, 2.0), P=1.0, in lean mass, MAD -1.3kg (-3.0, 0.5), P=.39, and in appendicular lean mass, MAD -0.1kg/m(2) (-0.3, 0.1), P=.45, were no longer apparent. During observation, cases lost more lean mass, MAD -3.7kg (-5.5, -1.9), P=.0005, and appendicular lean mass, MAD -0.5kg/m(2) (-0.8, -0.3), P<.0001 compared to controls. ConclusionsThe favourable effects of testosterone on body composition in men subjected to a concomitant weight loss programme were not maintained at 82weeks after testosterone treatment cessation.