Even more importantly it also worked on normal mice fed a high fat diet - reducing adiposity, or "visceral fat".
This opens the door to a way of combating the obesity epidemic, in general.
The treatment boosted lungs, physical activity and "brown fat" - the good type that reduces damaging "white fat" and is caused by heat production, or "thermogenesis."
Beyond combating menopause symptoms
Researchers said the antibody, reported in Nature, may lead to a therapy that can stave off a host of conditions.
These range from metabolic syndrome - a collection of symptoms such as high blood pressure and cholesterol - to cardiovascular disease, cancer and diabetes.
It could also stop polycystic ovary syndrome, a hormone disorder linked to weight gain that causes infertility, Professor Mone Zaidi said: "Menopause is associated with bone loss and enhanced visceral adiposity. An antibody that targets FSH increases bone mass in mice.
"Here, we report this antibody sharply reduces adipose tissue in mice. The antibody also causes profound beiging, increases cellular mitochondrial density, activates brown adipose tissue and enhances thermogenesis.
These actions result from the specific binding of the antibody to FSH to block its action.
"Our studies uncover opportunities for simultaneously treating obesity and osteoporosis."
Why does menopause cause weight gain?
Piling on the pounds is a common symptom of menopause. Changes in the body result in a slower metabolism, making it more difficult to build and maintain muscle mass.
Weight distribution also shifts, causing more fat to accumulate around the stomach, visceral fat, rather than around the hips and legs.
An answer to osteoporosis too?
The trials in the mouse model of menopause found the antibody helped boost bone mass and reduced body fat.
Prof Zaidi's team showed the antibody, dubbed Hf2, works by blocking a hormone called FSH (folicle-stimulating hormone) which is released by the pituitary gland.
Immediately after the menopause circulating FSH levels become elevated. Dr Zaidi said it's during this period bone loss "occurs most rapidly."
Osteoporosis mainly affects post-menopausal women because of the loss of bone-strengthening oestrogen.
Dr Zaidi said: "There's also a sharp increase in visceral adiposity during this life stage, which coincides with the emergence of disrupted energy balance and reduced physical activity.
"While the subsequent decline in oestrogen explains menopausal bone loss in large part, the effects of oestrogen deprivation on visceral fat and whole-body metabolism remain less clear.
"We therefore investigated whether, by targeting FSH, we could not only prevent bone loss but also reduce visceral adiposity and improve energy homeostasis."
In addition the treatment also reduced adiposity in normal mice fed the high-fat diet.
They showed increases in oxygen consumption, physical activity and "brown fat".
Benefits for general medical conditions
The researchers said current anti-obesity drugs work by reducing appetite or blocking nutrient absorption but have limited success and can cause side effects.
Dr Zaaidi said further research is needed to determine whether the findings will translate to humans.
But the study could aid the development of a single drug to help treat both post-menopausal osteoporosis and weight gain - and obesity in general.
He said: "A humanised Hf2 or its equivalent may not only be efficacious in reducing visceral and subcutaneous fat in people but might also provide benefit for certain medical conditions associated with visceral adiposity, such as metabolic syndrome, cardiovascular disease, cancer, diabetes and polycystic ovarian syndrome.
"Finally, in view of concurrent osteo-protection, we envisage a potential role for an FSH-blocking agent in treating both post-menopausal osteoporosis and obesity."
