Obesity is defined as having a body mass index (BMI) of 30 and over and being overweight is defined as having a BMI of 25 to 29.99. Weight gain and obesity develop when the energy intake from food and drink exceeds energy expenditure from physical activity and other metabolic processes.
Obesity is a risk factor for cancer, as well as many other chronic diseases such as cardiovascular disease and type 2 diabetes.
There is convincing evidence that overweight and obesity are risk factors for cancers of the colorectum, kidney, pancreas, oesophagus, endometrium and breast (in postmenopausal women). Excess body fat probably increases the risk of gallbladder cancer and there is limited suggestive evidence that overweight and obesity increases the risk of liver cancer. However, excess body fat probably decreases the risk of pre-menopausal breast cancer.
Cancer Council supports the recommendations in the National Health and Medical Research Council Dietary Guidelines for Adults in relation to body weight. Cancer Council recommends people maintain a healthy body weight within a BMI range of 18.5 to 25, and have a waist measurement less than 80cm for women and less than 94cm for men.
To achieve and maintain a healthy weight, Cancer Council recommends regular physical activity, increased incidental activity and eating according to energy needs. Serving moderate portion sizes and making fruit, vegetables, high fibre cereals and other low fat foods the basis of the diet may assist with achieving and maintaining a healthy body weight.
In addition, mothers are encouraged to breastfeed infants exclusively for up to six months and continue with complementary breastfeeding thereafter, as breastfeeding can help to prevent overweight and obesity in children and protect mothers from breast cancer.