Hate the spare tyre around your middle? In case you need another reason to start the diet, experts say that being overweight increases your risk of developing cancer.
See also: Women and cancer: symptoms you should never ignore
See also: Men and cancer: symptoms you should never ignore
Researchers from Imperial College London reviewed more than 2,000 studies, looking for a link between weight gain, body mass index, waist circumference and 36 different types of cancers.
They found "strong evidence" to suggest that being fat increases your chances of developing certain types of cancer. The 11 cancers are: oesophageal, colon, rectal, pancreatic, womb, kidney, multiple myeloma, breast, stomach, ovarian and biliary tract.
Published in the British Medical Journal, the study found that the risk is greatest for cancers of the digestive organs and parts of the body related to hormones.
Those at most risk
The higher your BMI, the more your risk of developing cancer increases. However, experts warn that anyone who carries excess fat – which is most people in the UK – is at some degree of risk.
For cancers of the biliary tract system (liver, gall bladder and bile duct), the risk goes up 56 per cent for every five unit rise in body mass index. (A five unit increase is enough to take a person from a healthy BMI of 20 to an overweight BMI of 25, or from an overweight BMI of 25 to an obese BMI of 30.)
In men, the risk of developing bowel cancer went up by 9% for every 5kg/m2 increase in BMI, while for women not on HRT, the risk of developing postmenopausal breast cancer shot up by 11%.
While this particular study didn't look into why being overweight increases the risk of some cancers, scientists know that carrying too much fat disrupts the body's hormonal and metabolic pathways. Excess fat is also linked to higher oestrogen and insulin levels in the body, as well as inflammation – all of which are known to increase the risk of cancer developing.
Fears for the future
Cancer is a leading cause of death around the world, and being overweight is second only to smoking as the biggest preventable cause. Unfortunately, we're getting fatter as a nation - and the rate of obesity has more than doubled over the past 40 years. Yet as many as 25,000 cases of cancer could be prevented every year in the UK alone if everyone was a healthy weight, according to World Cancer Research Fund.
Commenting on the research findings, Marc Gunter from the International Agency for Research on Cancer said: "I think now the public and physicians really need to pay attention to obesity with respect to cancer.
"Telling people to avoid being overweight not only reduces their risk of, say, diabetes and cardiovascular disease, it also reduces their risk of many different cancers."
Dr Alison Tedstone, chief nutritionist at Public Health England, added: "Less than half the population realise that being obese increases the risk of cancer and, with almost two-thirds of adults carrying excess weight, this is worrying."