Conclusions and Relevance This systematic review and meta- analysis did not show a significant beneficial or detrimental association of HT with muscle mass .
Importance Hormone therapy ( HT ) has been suggested for protection against age-related muscle weakness in women .
However , the potential for HT-associated health risks necessitates a better underst and ing of the direction and magnitude of the association between HT and health outcomes , such as lean body mass ( LBM ) .
Objective To determine whether HT was associated with reduced LBM loss compared with not receiving HT  among postmenopausal women aged 50 years and older .
Hormone replacement therapy dissociates fat mass and bone mass, and tends to reduce weight gain in early postmenopausal women: a randomized controlled 5-year clinical trial of the Danish Osteoporosis Prevention Study.
The aim of this study was to study the influence of hormone replacement therapy ( HRT ) on weight changes , body composition , and bone mass in early postmenopausal women in a partly r and omized comprehensive cohort study design . A total of 2016 women ages 45 - 58 years from 3 months to 2 years past last menstrual bleeding were included . One thous and were r and omly assigned to HRT or no HRT in an open trial , whereas the others were allocated according to their preferences . All were followed for 5 years for body weight , bone mass , and body composition measurements . Body weight increased less over the 5 years in women r and omized to HRT ( 1.94 + /- 4.86 kg ) than in women r and omized to no HRT ( 2.57 + /- 4.63 , p = 0.046 ) . A similar pattern was seen in the group receiving HRT or not by their own choice . The smaller weight gain in women on HRT was almost entirely caused by a lesser gain in fat . The main determinant of the weight gain was a decline in physical fitness . Women opting for HRT had a significantly lower body weight at inclusion than the other participants , but the results in the self-selected part of the study followed the pattern found in the r and omized part . The change in fat mass was the strongest predictor of bone changes in untreated women , whereas the change in lean body mass was the strongest predictor when HRT was given . Body weight increases after the menopause . The gain in weight is related to a decrease in working capacity . HRT is associated with a smaller increase in fat mass after menopause . Fat gain protects against bone loss in untreated women but not in HRT-treated women . The data suggest that women 's attitudes to HRT are more positive if they have low body weight , but there is no evidence that the conclusions in this study are skewed by selection bias
Conclusions and Relevance This systematic review and meta- analysis did not show a significant beneficial or detrimental association of HT with muscle mass .
Importance Hormone therapy ( HT ) has been suggested for protection against age-related muscle weakness in women .
However , the potential for HT-associated health risks necessitates a better underst and ing of the direction and magnitude of the association between HT and health outcomes , such as lean body mass ( LBM ) .
Objective To determine whether HT was associated with reduced LBM loss compared with not receiving HT  among postmenopausal women aged 50 years and older .