A new British study has shown that 6% of cancers globally are thought to be due to the combined effects of diabetes and high body-mass index, or BMI.
Worryingly, it also showed that women were at twice the risk of men of developing cancer due to the combined effects.
Conducted by the School of Public Health at Imperial College, London, and published in The Lancet Diabetes & Endocrinology, the research is the first of its kind to look at the combined health burden of both risk factors.
BMI provides an approximate measure of a person's body fat and is an internationally recognised method of measuring overweight or obesity levels. High BMI and diabetes are two risk factors – attributes or characteristics that increases an individual's likelihood of developing a disease – which are associated with illnesses, in particular some cancers.
The research results showed that in 2012, 792,600 new cases of cancers were attributable to the pooled effects of diabetes and high BMI.
The cancer risk from diabetes and high BMI was twice as high for women compared with men, and was responsible for 38% of new cases of endometrial (womb) cancer.
As an individual risk factor, twice as many cancer cases were attributable to high BMI, compared to diabetes (544,300 versus 280,100 cases).
Jean Hailes endocrinologist Dr Sonia Davison says the research shows "a compelling and worrying link between cancer, diabetes and high BMI".
"This is important to understand, given the increasing prevalence of obesity and diabetes in Australia and globally," Dr Davison says.
"The fact that the burden disproportionately affects women, and that high BMI as an individual risk factor causes double the number of cancers as diabetes, are key pieces of information to help guide change."
Of the number of cancer cases attributable to high BMI and diabetes for men, liver cancer was the highest – contributing over a third (43%) – followed by colorectal cancer (21%). In women, breast cancer made up the largest portion of cases at 30%, followed by endometrial cancer at 25%.
In Australia, almost two-thirds of adults (11.2 million) are overweight or obese, and around 6% (1.2 million) are living with diabetes. Globally, about 422 million and two billion adults respectively have diabetes or are overweight or obese.
Since both diabetes and high BMI are on the rise in most countries, the research calls for an increase in clinical and public health interventions to boost preventative and screening measures.
BMI is a modifiable risk factor, which means that it can be changed (unlike risk factors such as age or family history). While also a risk factor for cancer, high BMI is also a risk factor for diabetes and other chronic illnesses such as cardiovascular disease.
"What this research tells us is that lifestyle measures can reduce the risk of cancer," says Dr Davison. "However, it is not merely enough to encourage individuals to eat healthily and to exercise. It calls for a collective approach from policy makers, health practitioners and the community to help at-risk people make the necessary changes.
"While more research is required to understand the exact interaction between high BMI, diabetes and cancer, the take-away from this research is that we can do much more to prevent cancer."