Characterization of the effect of naltrexone/bupropion on body composition.

Aims: Oral treatment extended-release naltrexone/bupropion (NB) leads to significant weight loss, but its effect on body composition remains unclear. We investigated changes in body composition with dual-energy x-ray absorptiometry after treatment with NB or placebo in a subgroup of participants from a randomized control phase 3 study (COR-I).

Materials And Methods: Observed changes from baseline to week 52 were estimated for total, lean, and fat mass. Changes in body composition were evaluated using linear regression and adjusted for baseline covariates.

Results: The analysis included 82 participants (placebo, n = 26; NB, n = 56) with comparable baseline characteristics (age, BMI, sex). The NB group experienced a significant -7.8% change of total mass (-12.9% change in fat mass and -4.1% in lean mass), compared with a -2.8% change of total mass (-4.8% change in fat mass and -1.4% in lean mass) in the placebo group. The adjusted changes in lean-to-fat mass ratio of 0.069 in the NB group and -0.056 in the placebo group were significantly different (p < 0.05).

Conclusions: NB-induced weight loss is associated with significant reductions in total percent fat mass, increase in total percent lean mass, and change in lean-to-fat mass ratio, in comparison to placebo. Larger studies are needed to further elucidate the clinical significance of these changes and impact of a potentially healthier metabolism.