Obesity and diabetes ‘causes up to 800,000 cancers worldwide each year’

Study is first time scientists used body mass index to calculate global cancer burden

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Two of the most common lifestyle-related conditions cause almost a million new cancers worldwide each year, a study has found.

Diabetes and excess weight were responsible for nearly 800,000 newly diagnosed cancers, including those affecting the liver, breast, bowel and womb.

It is the first time scientists have estimated the worldwide cancer burden caused by being overweight or obese, as defined by a high body mass index (BMI), and the metabolic disease thought to affect more than four million people in the UK.

The vast majority of diabetes cases are the Type 2 form, which is strongly linked to lifestyle - poor diet, excess weight and inactivity - as well as genetics

Researchers led by a team from Imperial College London found that nearly 6% of new global cancer cases in 2012 resulted from the combined effects of diabetes and being overweight or obese.

On its own, being overweight was responsible for almost twice as many cancers as diabetes - 544,300 versus 280,100 cases.

Cancers linked to the two conditions were also nearly twice as common in women than in men.

Excess weight and diabetes together accounted for a quarter of all liver cancers and a third of endometrial cancers, which affects the lining of the womb.

If current trends continue, the share of cancers attributable to the two risk factors will increase by more than 30% in women and 20% in men by 2035, say the study authors.

Lead researcher Dr Jonathan Pearson-Stuttard, from Imperial's School of Public Health, said: "While obesity has been associated with cancer for some time, the link between diabetes and cancer has only been established quite recently.

"Our study shows that diabetes, either on its own or combined with being overweight, is responsible for hundreds of thousands of cancer cases each year across the world."

How diabetes can trigger cancer is still being investigated but high insulin and blood sugar levels, chronic inflammation and sex hormone disruption may all play a role, the scientists believe.

The study, published in The Lancet Diabetes & Endocrinology journal, is based on an analysis of data from 175 countries in 2012. Rates of 12 different types of cancer were combined with population figures for high BMI and diabetes.

In men, liver cancer was the most common cancer linked to diabetes and high BMI, followed by bowel cancer.

or women, breast cancer and endometrial cancer had the strongest link with diabetes and being overweight. Breast cancer accounted for nearly 30% of cancers thought to be caused by the conditions.

Dr Pearson-Stuttard added: "Both clinical and public health efforts should focus on identifying effective preventive, control and screening measures to structurally alter our environment, such as increasing the availability and affordability of healthy foods, and reducing the consumption of unhealthy foods.

"It is vital that co-ordinated polices are implemented to tackle the shared risk factors and complications of chronic diseases such as obesity and diabetes."

Dr Emily Burns, from the charity Diabetes UK, said: "Diabetes doesn't directly cause cancer, but this study adds to the evidence that having diabetes can increase risk of certain types of cancer. We also need to recognise the individual types of diabetes, and understand how they might affect the risk of cancer differently.

"With almost 12 million people in the UK at risk of Type 2 diabetes, it's vital that people are supported to reduce their risk. You can lower your risk of Type 2 diabetes and cancer by maintaining a healthy weight, eating well, keeping active, not smoking, and sticking to the recommended alcohol consumption guidelines."

Press Association