It was known for centuries that regular exercise keeps one healthy. Several studies have shown that regular aerobic exercise combined with a low-calorie diet can help people to lose weight and keep it off. Even when a person doesn’t eat less, aerobic exercise results in small amounts of weight loss and a significant reduction in intra-abdominal fat (a dangerous fat that forms deep in the central part of the body and is associated with increased risk of several diseases).
Obesity in the middle, as it is popularly known, is clearly shown to be associated with several cancers.
It is being increasingly realised that that being obese (extremely overweight, defined as having a Body Mass Index or BMI of 30 or higher) increases a person’s risk of developing and dying from many types of cancers. This risk especially includes postmenopausal breast cancer, prostate cancer, colon cancer, uterine cancer, kidney cancer, and some types of oesophageal cancers. Interestingly, the entity called insulin resistance—when the body doesn’t respond to insulin properly resulting in a rise in blood sugar—increases the risk of some cancers. Exercise has been shown to improve insulin resistance.
On-going low-grade inflammation and chronic inflammatory diseases, such as inflammatory bowel disease, are associated with several cancers. Once again exercise may help reduce inflammation, which may help lower the risk of cancer. Similarly moderate-intensity exercise has been shown to improve the function of the immune system, which may protect against infectious disease and cancer.
Being overweight and inactive also increases the risk of cancers regulated by hormones, such as breast and uterine cancers. For instance, overweight and obese postmenopausal women have higher levels of oestrogen in the blood compared with slimmer postmenopausal women. One clinical trial (research study involving people) found that postmenopausal women who were inactive and overweight or obese had their hormone levels drop after exercising for 45 minutes each day, five days a week, for 12 months. However, the hormone levels dropped only in women who had also lost body fat, suggesting a connection between exercise, hormone levels and body fat.
Excess body weight is one of the strongest risk factors for endometrial (mucous membrane that lines the uterus) cancer and accounts for about 50 percent of the cases in Europe and in the USA. Obese women (BMI more than 30 kg/m2) have a threefold increased risk of developing endometrial cancer compared to normal weight women. Several biological mechanisms could mediate the association between obesity and endometrial cancer risk. In postmenopausal women, excess weight leads, through peripheral conversion of androgens, to increased circulating bioavailable oestrogens which in turn, when not counterbalanced by progesterone, increases the mitogenic (cell division) activity of endometrial cells.
In premenopausal women, obesity has been associated with the development of polycystic ovary syndrome, a disease that affects four to eight percent of women. It is characterised by ovarian hyperandrogenism (a condition associated with high male hormone levels, characterised by the accumulation of numerous fluid-filled cysts on the ovaries), chronic anovulation (absent ovulation), and other metabolic disturbances), anovulation (the absence of ovulation due to immaturity, post-maturity, pregnancy, oral contraceptive ;pills or dysfunction of the ovary), and progesterone deficiency.
Obesity-associated hyperinsulinemia (excess levels of circulating insulin in the blood) might also play an important role in endometrial carcinogenesis (process by which normal cells are transformed into cancer cells), in both pre and postmenopausal women, either directly, by stimulating endometrial cell proliferation, or indirectly, through the sex steroid and the insulin-like growth factor 1 pathways.
More recently, it has been proposed that other adiposity-related (having the property of containing fat) factors such as cytokines and adipokines (protein molecules that regulate the immune system) might contribute to endometrial cancer initiation and progression and to the obesity-related increase in risk. Excess body weight is associated with a systemic low-grade inflammatory condition characterised by elevations in circulating pro-inflammatory cytokines and acute phase proteins. Inflammatory processes also play a central role in the regulation of endometrial mucosa growth and shedding during the menstrual cycle as well as in endometrial repair following menstruation.
Exercise can help lower obesity and decrease oestrogen levels. Both obesity and elevated oestrogen levels are factors that may be related to uterine cancer development. Some studies have found a 30 to 40 percent reduced risk of this type of cancer in active women. Hence, every woman should initiate a conscious effort to incorporate regular exercise in her daily routine. A simple walking program is a great beginning. Of course, a trim and attractive look is an added attraction for starting.