John Speakman produced some research in 2008 that showed that people in the UK are exercising as much today as they did 25 years ago and suggesting the only way to fight obesity is to eat less. After a couple of lectures this year, the Aberdeen University professor’s work has been back in the news.

He found that in the UK the average calorie content of food we buy had increased by 12 per cent over the same period. In the US the rise was 25 per cent.

“People would have to exercise for four to five hours a day,” he says, “in order to lose the weight that these extra calories cause.”

What the food companies put in, they can also take out. As concern builds over what obesity regulation will mean for retailers, expect major manufacturers to innovate their way back to the calorie content of foods 25 years ago as Mars already have done with their latest Mars bar: “Same delicious taste, 45% less Saturated fat”.