Older women already know menopause may slow metabolism and cause weight gain. Now new research from the university of Colorado suggests that low sex hormones may affect weight gain in younger women too. When researchers reduced estrogen and progesterone using pharmacologic therapy, women burned 42 calories less per day. Can low sex hormones result in lasting metabolic damage? Thats what researchers plan to find out. The findings could help shape future hormonal and weightloss treatments.