A study by Dr Andrew Renehan of the University of Manchester and Christie Hospital NHS Foundation Trust, published in the Lancet, found the level of risk from an increased Body Mass Index (BMI) can vary between sexes and ethnic groups.

A person with a BMI of 25 or over is categorized as overweight, while someone with a BMI of more than 30 is considered obese.

Excess body weight is increasingly seen as a risk factor for some kinds of cancers. This is backed up by the study, which looked at 282,137 cases to determine the risk of cancer of those with a 5kg per square metre increase in BMI.

Such an increase was found, in men, to raise the risk of colon and kidney cancers by 24%, thyroid cancer by 33% and oesophageal adenocarcinoma by 52%.

In women, the same increase meant the risk of both endometrial cancer and cancer of the gallbladder rose by 59%, oesophageal adenocarcinoma by 51%, and kidney cancer by 34%.

The chances of men with an higher BMI developing rectal cancer and malignant melanoma also rose, as did the risk of women getting post-menopausal breast, pancreatic, thyroid, and colon cancers.

The risk of leukaemia, non-Hodgkin's lymphoma and multiple myeloma rose in both sexes.

The association between increased BMI and breast cancer in Asia-Pacific populations was stronger than in any other ethnic group.

Commenting on the study, epidemiologists Dr Susanna Larson and Professor Alicja Wolk said, "The number of deaths per year attributable to obesity is about 30,000 in the U.K. and 10 times that in the U.S., where obesity has been estimated to have overtaken smoking in 2005 as the main preventable cause of illness and premature death.

"Efforts will be needed to increase education on diet and physical activity."

From the February 18, 2008, Prepared Foods e-Flash