LONDON: Women who are overweight for more than 10 years have a higher risk of cancer, a leading scientist warns.
The chance of getting potentially deadly forms of the disease also increases as a person’s weight goes up, data revealed.
On average every 10 years of being fat upped the odds of cancer by 7 percent.
But for women who were severely obese the risk of breast cancer rose by 8 percent every decade and womb cancer by 37 percent.
Excess weight is thought to feed at least 10 types of cancer, including breast, womb, bowel, pancreatic and kidney. Despite advances in medicine the disease claims more than 160 000 lives a year in the UK, where 60 percent of English women are overweight or obese.
Melina Arnold, of the International Agency for Cancer Research in Lyon, France, said it is important to make people aware of the obesity link, especially as once weight is put on it is hard to lose.
World Health Organisation researcher Arnold, who worked with US colleagues, analysed data on almost 75 000 post-menopausal American women whose health was tracked for around 12 years.
They provided measurements from when they were 18, 35 and 50 years old. Some 40 percent of the women had always been slim.
This left 60 percent who had been overweight at some point, with almost half of these obese.
Some 6 300 of the women were diagnosed with cancer. And the longer they had been overweight, the higher their odds of the disease.
The figures for endometrial cancer, which affects the lining of the womb, were particularly striking. The odds of the disease rose by 17 percent on average for every decade a woman was overweight.
But for a severely obese woman the risk increased by 37 percent.
BMI is a measurement of weight related to height. Below 25 is healthy, between 25 and 29.9 overweight and 30-plus obese.
A 1.6m who weighs 57kg has a healthy BMI of 22.3. But at 69kg her BMI is 27.3 and she is overweight.
If her weight creeps up to 79kg her BMI goes into the obese range at 31. At 88kg she would have a BMI of 35 and classed as severely obese.
It is thought hormones released by fat in the body feed tumours.
The immune system may also release harmful chemicals and DNA may be damaged more, raising the odds of cancer.
In PLOS Medicine, Arnold said it is important that women are aware of the link.
"If we can prevent overweight and obesity from early on and promote maintaining a healthy weight, this would probably be a good strategy to reduce the prevalence of overweight and increase health."
Fiona Osgun, of charity Cancer Research UK, said: "Obesity is the single biggest preventable cause of cancer after smoking and is linked to 10 different types.
"This study only studied women, but we know from other research that keeping a healthy weight can help reduce men’s risk of the disease too."