LONDON, England (The Times), November 7, 2007:Women who are overweight are at a greater risk of contracting a wide range of cancers, a study has shown, writes Nigel Hawkes, Health Editor in The Times
The authors of the study calculate that 6,000 cancers a year – 5 per cent of all cancers in women – can be attributed to being overweight or obese.
The effect is greatest in cancers of the oesophagus (gullet) and endometrium (lining of the womb), where the risks are more than doubled. But there are also significant increases in the risks of contracting kidney cancer, leukaemia, multiple myeloma, pancreatic cancer, non-Hodgkin’s lymphoma, ovarian cancer, breast cancer in older women and colorectal cancer in younger ones.
The team, led by Gillian Reeves of the Cancer Epidemiology Unit at Oxford, analysed data from the Million Women Study. This is the largest study of the cancer risk for women, funded by Cancer Research UK. It involved 1.2 million women who were aged between 50 and 64 when they joined the study between 1996 and 2001, and who were monitored for an average of more than five years.
Information provided by the women at the start of the study included their height and weight, There were more than 45,000 cases of cancer and 17,203 deaths. The data allowed correlations to be observed between body mass index and cancer risk. The report, published in the British Medical Journal, showed that greater weight increased the risk of ten of the 17 cancers studied.
It was calculated that an increase of 10 in the BMI measure – from 25 to 35, say – increased the risk of all cancers combined by 12 per cent.
It almost tripled the risk of endome-trial cancer and more than doubled that of oesophageal cancer.
Dr Reeves said: “Based on our findings, 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.
“Our research also shows that being overweight has a much bigger impact on the risk of some cancers than others. Two thirds of the additional 6,000 cancers each year due to overweight or obesity would be cancers of the womb or breast.”
In some cases, the effect depends on the age of the woman. For example, being overweight only increases the risk of breast cancer after the menopause and the risk of bowel cancer before the menopause.
Sara Hiom, of Cancer Research UK, said: “This research adds to the evidence regarding the impact of being overweight or obese on developing cancer and dying from the disease. While most people readily associate carrying extra weight with being a general health risk, many do not make a specific link with cancer. These findings need to be taken into consideration alongside the established strong relationships between body fatness and other common illnesses, such as diabetes and heart attacks.”
The link between cancer and being overweight is not new, but this is among the strongest evidence yet gathered in support of it. The study does not address reasons for the link, but a strong possibility is that extra fat generates greater quantities of the hormones that feed cancer.
Excess body fat is not simply padding but active tissue producing hormones, so someone who has more of it runs a higher risk of cancer than a person of normal weight.
In addition, overweight people are less likely to have healthy lifestyles. A healthy diet and regular exercise are acknowledged as factors that lower the risk of all cancers.
© Copyright 2007 Times Newspapers Ltd.
