Researchers have found that hitting menopause causes women to lose their natural supply of the female hormone oestrogen, resulting a shift of fat storage from the hips to the waist.
This may explain why some older women lose their hour-glass figures and become more apple-shaped, the Daily Mail reported.
The review by the International Menopause Society also found that, contrary to popular belief, hormone replacement therapy doesn't cause women to put on weight - and can in fact help prevent abdominal fat increasing.
"It is a myth that the menopause causes a woman to gain weight," the paper quoted review leader Professor Susan Davis of Monash University, Melbourne, Australia as saying.
But there is no doubt that the new spare tyre many women complain of after menopause is real, and not a consequence of any changes they have made.
"Rather, this is the body's response to the fall in oestrogen at menopause - a shift of fat storage from the hips to the waist," Davis stated.
Lose natural supply of oestrogen after the menopause can also lead to hot flushes, mood changes and night sweats.
The researchers found women tend to gain, on average, around 1lb a year throughout their midlife.
The review also found higher levels of abdominal fat increase the risk of future metabolic disease, such as diabetes and heart disease, in postmenopausal women.
The IMS is calling for women to be more aware of the problems associated with excess weight, and to take early steps to ensure they don't gain too many pounds after the menopause.
"What this translates to in real terms is that women going through the menopause should begin to try to control their weight before it becomes a problem, so if you have not been looking after yourself before the menopause, you should certainly start to do so when it arrives," Professor Davis said.
"This means for all women being thoughtful about what you eat, and for many being more active every day," the researcher added.
The study, carried out to mark World Menopause Day on Thursday, has been published in the medical journal, Climacteric.