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

Abstract

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 pre-specified double-blind randomised placebo-controlled observational follow-up study of a randomized controlled trial (RCT). Participants were men with baseline obesity (body mass index ≥ 30kg/m²) and a repeated total testosterone level ≤ 12nmol/L, previously enrolled in a 56-week testosterone-treatment trial combined with a weight loss program. 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 randomised 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=0.51. 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=0.04, but had lost less lean mass MAD 3.4kg (1.3, 5.5), p=0.002. At 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=0.39, and in appendicular lean mass, MAD -0.1kg/m² (-0.3, 0.1), p=0.45, were no longer apparent. During observation, cases lost more lean mass, MAD -3.7kg (-5.5, -1.9), p=0.0005 and appendicular lean mass, MAD -0.5kg/m² (-0.8, -0.3), p<0.0001 compared to controls.

Conclusions

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

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