The sedentary, screenwatching, fast food eating culture of our times, which leads to excess weight gain, is putting people at risk not just of heart problems and diabetes but also of cancer, according to a leading medical journal.
The more excess weight men and women put on, the more their chances increase of getting certain types of cancer, says a review in the Lancet's cancer journal, Lancet Oncology, published today.
The risk of breast cancer, cancer of the womb lining, and colon, kidney and oesophageal cancers, rises as people pile on the pounds.
The journal, in an accompanying editorial, warns that the obesity epidemic - or "globesity" as the World Health Organisation termed it recently - threatens a public health crisis. The WHO is calling for affluent countries such as the UK to try harder to alter people's attitudes so they understand the pressing need to keep their weight down.
The authors of the review, Franca Bianchini, Rudolf Kaaks and Harri Vainio, of the International Agency for Research on Cancer (IARC), at Lyon in France, say governments, schools, employers, the media and others, should all play a part in changing the environment to one less conducive to getting fat.
"Avoidance of weight gain should become one of the mainstays of chronic disease prevention in modern societies," they write.
About half of all men and 35% of women in Europe are considered to be overweight, as measured by doctors calculating individual body mass index (BMI) - which, in metric measurement, is a person's weight in kilograms divided by their height in metres squared. A healthy BMI level is considered to be between 18.5-25 for adults; above this index a person is considered overweight, and, at a reading of 30, obese.
Obesity increased in the UK by 10% between 1987 and 1997. In parts of west Europe and the US, one in five people is obese.
The IARC team says that large numbers of new cancers could be avoided if people kept their weight down through diet and exercise. About 40% of endometrial cancers, close to 25% of kidney cancers and about 10% of breast and colon cancers would not develop if people kept their weight within the normal range.
Each year within the EU, obesity is responsible for 35,000 new cases of cancer, the team says.
In postmenopausal obese women, the risk of breast cancer goes up by between 20% and 40%, they add, and the risk rises with age. The risk of endometrial cancer in overweight women is increased by between 200% and 400%. The risk of kidney cancer can double in those with a high BMI.
The scientists say the relationship between fat and cancer suggests that excess calories may be a big problem.
Animal studies have shown that restricting calorific intake can protect against development of tumours. "There is evidence that individuals who take regular physical activity are protected against cancers of the breast, colon and possibly endometrium."
The researchers also say: "About half of the adult population of industrialised countries are insufficiently active in their leisure time and one quarter to one third can be classified as totally inactive."
There is evidence that regular exercise alone can reduce cancer risk.
An editorial in the same Lancet journal accuses governments of only half-hearted efforts to encourage healthy weight levels.
"Governments are still ignoring issues that would make a real difference," it says. "Long working hours and high-pressure environments ... contribute to the general decrease in leisure time and prohibit regular exercise or healthy cooking."
People must be told that healthy living is a necessity not a choice, the editorial says.
However, overweight people can be stigmatised and defiant groups exist defending "the right to be fat". The editorial says there could be a public health crisis "if the lack of practical solutions means governmental policies run at odds to people's personal goals". With effort focused on anti-obesity drugs and quick-fix economic strategies, adequate solutions to weight gain may still be a long way off.
