More than 2,500 people a week would avoid being diagnosed with cancer if they made lifestyle changes, such as exercising and lowering their weight, research suggests.

Nearly 40 per cent of all cancers diagnosed in the UK every year could be avoided, a new report by Cancer Research UK has found.

Smoking is the biggest avoidable cause of cancer, followed by excess weight, overexposure to UV radiation from the sun and sunbeds, drinking alcohol, eating too little fibre, and outdoor air pollution.

Experts presenting the data warned that with smoking rates continuing to go down and rates of obesity on the increase, obesity could overtake smoking as the biggest killer.

Cancer Research UK chief executive Sir Harpal Kumar said: "Obesity is potentially the new smoking, if we're not careful.

"My sense would be it'll be some time in next couple of decades that we'll see those two switch around."