Piling on the pounds is three times more deadly for men than women and even being slightly overweight raises the risk of dying early, the biggest ever study into weight and death has shown.

Obese people can expect to lose three years of life while the average overweight person will die 12 months sooner than they would have if they were a healthy size, researchers at Oxford, Cambridge and Harvard universities found.

Usually fewer than one in five men will die before the age of 70, but that jumps to nearly one in three for the moderately obese, and eight in 10 for the morbidly obese.

In contrast around one in 10 women can expect to die early, with obesity raising the risk to one in seven. While obesity raises the risk of early death by just three per cent for women, it is 10 per cent for men, more than three times as much.