Black cohosh is not considered a way to control weight, and instead may actually cause weight gain, according to WebMD. Black cohosh contains phytochemicals that create an effect in the endocrine system similar to that of estrogen, and it is typically used to mediate symptoms of menopause or menstrual pain.
The specific mechanism of the phytochemicals in black cohosh that affect the endocrine system are unknown. However, the endocrine system plays a large role in metabolism function, explains Prevention. Any effects on the endocrine system may have an indirect effect on metabolism and weight.
Some black cohosh products can modestly reduce some symptoms of menopause, such as hot flashes. Most research conducted on the positive effects of black cohosh is for the commercial product Remifemin, a standardized root extract that users take twice a day. Health food stores also carry root, extract and tincture forms of black cohosh. However, according to WebMD, some clinical studies have concluded that black cohosh products other than Remifemin have no greater effect on symptoms of menopause than placebo pills.
Black cohosh is widely used in the United States, Australia and Germany, where it is approved as a prescription alternative to hormone therapy, states WebMD. The side effects of black cohosh may include stomach discomfort, rash, vaginal bleeding and weight gain.