A British expert says that although exercise is important for reducing the risk of osteoporosis and heart disease in post-menopausal women, too much exercise in pre-menopausal women may actually increase the risks.
Dr Karen Birch, Senior Lecturer in Exercise Physiology at the University of Leeds, says that from puberty to the menopause, females produce a cycle of the reproductive hormones oestrogen and progesterone, and these hormones interact with both health and physical activity.
Because oestrogen protects against the development of both osteoporosis and cardiovascular disease, it is very important.
Light to moderate physical activity enhances the beneficial effects of the reproductive hormones upon bone strength and the cardiovascular system and is linked with a decreased risk of disease and early death.
In recent large scale studies people who are overweight but not obese, but physically active, have been seen to have less risk of disease and disease-related death than those people who are normal weight but sedentary.
Dr Birch says it is essential that women exercise moderately before and during the onset of menopause, because post-menopause, the loss of the hormone oestrogen results in a reversal of the protective effects.
Then women’s bone mineral density begins to decrease, their arteries begin to stiffen, their cholesterol levels begin to rise and their risk of becoming diabetic increases.
She says these physiological changes are much slower in women who participated in an active lifestyle prior to the menopause than in those who were inactive.
However, any loss of exposure, for example by a delayed onset of menstruation or periods of time where menstruation ceases, can have a negative impact upon health and both of these events have been related to participation in high intensity or high volumes of physical activity.
According to recent research this problem is a result of the body switching off menstruation when energy intake from food is less than energy expenditure.
The results of high amounts of physical activity is a loss of fertility and a negative effect upon immediate and long term health.
Dr Birch stresses that the key for women seems to be to exercise in moderation, but to be sure to do some exercise.
Making the situation between physical activity, reproductive hormones and health more complex, is the impact of other sources of the hormone oestrogen, as oestrogen compounds can be found in food sources, the contraceptive pill and hormone replacement therapy (HRT).
In the past HRT was seen as a hugely positive product for protecting against bone loss in post-menopausal women, but recent research indicates the potential of HRT to increase the risk of both cardiovascular disease and breast cancer in women, and it is no longer used to protect against osteoporosis.
At a time when levels of obesity are rising and HRT use is falling, the effect of these two things will be detrimental to the health and well-being of many women.
Birch says if light-moderate intensity physical activity can reduce health risks by counteracting the effects of weight gain and loss of oestrogen it will be of great benefit to women.
Dr Birch will present her views at the BA Festival of Science on 8 September as a part of “Celebrity diets, obesity and hormones: what does science have to say?”