07 Nov 07

Five per cent of cancers in women can be attributed to obesity

Women who are overweight or obese are at a greater risk of contracting a wide range of cancers, according to a new report published today by the British Medical Journal.

The study, led by Dr Gillian Reeves, a Cancer Research UK epidemiologist based at the Cancer Epidemiology Unit at Oxford University, has calculated that 6,000 cancers a year, or five per cent of all cancers in women, can be attributed to being overweight or obese.

National Survey Data from the United Kingdom indicates that around 23 per cent of all women in England are obese, and 34 per cent are overweight. Excess weight is known to be associated with increased health risks and illnesses such as diabetes and heart disease, but less is known about its effects on cancer.

The Million Women Study, funded by Cancer Research UK, is the biggest study ever undertaken to look at women and cancer risk. Cancer Research UK researchers at Oxford University examined the relation between body mass index (BMI), cancer incidence, and mortality in 1.2 million UK women aged between 50 and 64 over a seven year period. More than 45,000 cases of cancer and 17,000 cancer deaths occurred during that time.

Dr Gillian Reeves, Cancer Research UK epidemiologist at Oxford University, said: ‘We estimate that being overweight or obese accounts for around 6,000 out of a total 120,000 new cases of cancer each year among middle-aged and older women in the UK.’

She added: ‘Our research shows also shows that being overweight has a much bigger impact on some cancers than others. Two thirds of the additional 6,000 cancers each year due to obesity would be cancers of the womb or breast.’

The researchers found that the link between weight and risk of cancer depended on a woman’s stage of life. Being overweight increases the risk of breast cancer only after the menopause and the risk of bowel cancer only before the menopause.

Half of all cases of womb cancer and a type of oesophageal cancer were examples where being overweight or obese is a major risk factor. The study also found that excess weight increases the risk of kidney cancer, leukaemia, multiple myeloma, pancreatic cancer, non-Hodgkin’s lymphoma, ovarian cancer, and, in some age groups, breast and bowel cancer.

Sara Hiom, Director of Cancer Research UK’s health information, said: ‘These findings need to be taken in consideration alongside the established strong relationships between body fatness and other common illnesses such as diabetes and heart disease.’