By Dr Richard Isaac, Medical Oncologist

Cancer remains one of the most common causes of death in New Zealand. While medical advances are improving survival and cure rates of different cancers, lifestyle factors have also been shown to significantly affect outcomes. Smoking, diet and even sexually transmitted diseases are known to be risk factors for developing certain cancers, but less recognised are the effects of body weight and exercise.

The link between physical activity and health benefits has been intuitively known throughout recorded time. Nevertheless, a lack of physical activity remains a major health problem and a large proportion of deaths in New Zealand remain related to a sedentary lifestyle with most focusing on diseases such as heart disease and diabetes. However, being overweight, termed as having an elevated body mass index or BMI >5kg/m2 (15kg above ideal for men and 13 kg in women) also increases the risks of developing cancer.  Obesity of this degree doubles the risks of oesophageal cancer in both sexes. In women it also doubles the risks of cancer of the uterus and gall bladder cancer and also has a significant effect on kidney cancer, with a minor increase in the risks of breast cancer after menopause and of colon cancer.  In men an elevated BMI also produces higher risks of thyroid, colon and kidney cancers.

A focus on sensible eating and regular exercise will enable weight loss and a reduction in these risks, as well as producing the known benefits for cardiac health and diabetes. Exercise alone has also been linked to reduced rates of certain cancers such as prostate cancer and breast cancer, two of the most common cancers in New Zealand.

Exercise also has important effects on outcome for those receiving chemotherapy. There is a common misconception that people receiving chemotherapy lose weight. In fact, of those women receiving chemotherapy after surgery for breast cancer, over 80 percent gain weight and in the USA 25 percent gain more than 11kg. Persistent weight gain is linked to a worse outcome from the cancer, if it can not be reversed.

At Palmerston North Hospital we are establishing a program to prevent such weight gain, using a combination of sensible diet and regular exercise. It is more effective to prevent weight gain with a such a regime, rather than attempting to lose weight at a time when people are often tired and recovering from intensive therapy.

A large study of 2987 nurses in the US also found that physical activity after a breast cancer diagnosis reduced the risks of death, most apparent in those women who walked three - five hours per week at an average pace.

It is clear that we do have some control over whether cancer affects our lives. We should all look to minimise our risks by eliminating smoking, eating a healthy diet and incorporating regular exercise into our daily routines.

Dr Richard Isaacs is a Medical Oncologist at Aorangi Hospital and MidCentral Health