HRT plus exercise cut fat mass most in postmenopausal women

Treatments aimed at bone loss after menopause are prescribed for fracture risk, but the same period of life brings shifts in body composition: lean mass tends to fall and fat mass tends to rise. Whether the widely used anti-osteoporosis approaches also influence those changes has been contested, and it matters because muscle and fat carry their own consequences for strength, function and metabolic health. Women deciding about hormone therapy or an exercise programme have an interest in knowing what else moves. This review set out to compare the options on lean and fat mass rather than on bone alone.

The authors searched PubMed, Embase, Scopus, Web of Science and Cochrane from inception to 26 March 2022 for clinical trials that used anti-osteoporosis treatments in postmenopausal women and reported changes in body composition. Only trials showing alteration in lean body mass or fat mass were included. Results were pooled as standardised mean differences, which express change on a common scale across studies that measured things slightly differently. The team then ran a network meta-analysis, a method that ranks treatments against each other by combining direct and indirect comparisons, to identify which option looked most effective.

Compared with placebo, hormone replacement therapy was associated with increased lean body mass, with a standardised mean difference of 0.32, and reduced fat mass, with a standardised mean difference of minus 0.30. Physical exercise training reduced fat mass, with a standardised mean difference of minus 0.66, but its effect on lean body mass was not statistically significant and the estimate was wide, at 1.31 with a range spanning both loss and gain. In the network analysis, oral estrogen and progestogen plus exercise ranked highest for reducing fat mass, with a cumulative ranking score of 99.9. The authors concluded that combining hormone therapy with exercise reduced fat mass while maintaining lean mass.

This supports the view that anti-osteoporosis treatment is not neutral for body composition, and puts numbers on effects that had previously been described as controversial. The exercise result for fat mass is consistent with what is already well established outside the menopause literature, while its unclear effect on lean mass here reflects how few trials measured it well. The top ranking for hormones plus exercise rests on indirect comparison, so it is a hypothesis about the best combination rather than a demonstration of it. A head-to-head trial with body composition as the primary outcome remains missing.

This is a reason to think that decisions about hormone therapy and exercise after menopause have implications for fat and muscle as well as for bone. The differences reported are modest and expressed on a standardised scale, so they should not be read as dramatic body recomposition. Exercise was the intervention with the clearest fat mass result, and the combination came out on top only in an indirect ranking. Any decision about hormone therapy is a clinical one, and nothing here speaks to who it is or is not appropriate for.