"So many women get confused when they start to gain weight during menopause, because their eating habits haven't changed," said Dr Amanda Sainsbury-Salis from Sydney's Garvan Institute of Medical Research.
"What the research shows clearly is that menopause causes a dramatic and sudden reduction in physical activity levels. Just prior to menopause, women halve their amount of activity compared to pre-menopause levels.
"So one reason women gain weight in menopause is because of a reduction in energy expenditure. Combine this with unchanged eating habits and weight gain is almost inevitable," she added.
The research also suggests that weight gain is directly related to the lack of oestrogen, which has dramatic effects on signals the brain sends to the body.
However, further studies are on to see what causes these effects and whether or not they continue long-term.
Researchers suggested that increasing the levels of physical activity can help prevent weight gain.
"A lot of women ask whether they can actively counteract that tendency. In fact, it's been shown that women who maintain or increase their level of physical activity during menopause tend to come out the other end without gaining weight."
"We don't know exactly why menopausal women stop moving as much. But we know it's not because of their age and the lifestyle constraints happening at that time of life.
"Another thing, when physical activity levels drop and your energy needs are less, it's really important to stay in tune with your hunger signals because you just don't need to eat as much in order to feel satisfied," she added.
Garvan's Professor Lesley Campbell, also Director of the St. Vincent's Diabetes Centre said that HRT could actually help protect women against harmful abdominal fat gain and the development of heart disease and Type 2 diabetes.
"During menopause, most women experience redistribution of fat, often gaining weight around the middle," said Campbell.
"As we have demonstrated in our research, abdominal fat is a risk factor in the development of cardio-metabolic diseases, such as diabetes.
"Prior to menopause, women have a lower risk of heart disease than men. Menopause equalises that risk.
"Women taking HRT appear to maintain their pre-menopausal risk levels," Campbell added.