British men are getting heavier, with the average man piling on more than a stone between 1986 and 2000 – and experts believe the weight gains are getting worse.

Research from Oxford University shows that the average man was 7.7kg (17lb) heavier in 2000 than he was in 1986. Women have not fared much better, with an average weight gain of 5.4kg.

While men have put on weight due to poor diet and a lack of exercise, women have piled on the pounds by simply eating too much, the researchers wrote in the British Journal of Nutrition. They analysed changes in food consumption and body weight.

NHS figures for 2008 in England, the most recent available, show that 25 per cent of men were classed as obese, compared with only around 7 per cent in 1986-87. Dr Peter Scarborough, who led the latest study, said: "Men spend more of their working lives sitting at desks now – manual careers are less common than they used to be."