Appreciating it would take four hours walking to burn the calories in a pizza or 22 minutes to run off a chocolate bar creates an awareness of the energy cost of food, they say, BBC reported.

The labels would help people indulge less, exploratory studies suggest.

The aim is to encourage healthier eating habits to fight obesity.

According to the researchers from Loughborough University, who looked at 14 studies, this type of labelling could cut about 200 calories from a person’s daily average intake.

This may not sound like much but, they say in the Journal of Epidemiology and Community Health, it would have an impact on obesity levels across the country.

More than two-thirds of adults in the UK are overweight or obese.

Lead researcher Professor Amanda Daley said: “We are interested in different ways of getting the public to make good decisions about what they eat and also trying to get the public more physically active.”

And labelling food with ‘exercise calories’ made it easier for people to understand what they were eating and nudge them into making better choices.

About calories

● The amount of energy in an item of food or drink is measured in calories (kcal)

● Our bodies need them to function

● But eating too many without burning them off causes obesity

● Eating a little bit too much every day adds up and the excess is stored by the body as fat

● Men need about 2,500 kcal a day and women about 2,000 kcal

Daley said many people would be shocked to realize how much physical exercise would be required to burn off calories from certain snacks and treats.

“We know that the public routinely underestimates the number of calories that are in foods,” she said.

“So if you buy a chocolate muffin and it contains 500 calories, for example, then that’s about 50 minutes of running.

“This definitely isn’t about dieting.

“It’s about educating the public that when you consume foods, there is an energy cost so that they can think, ‘Do I really want to spend two hours burning off that chocolate cake? Is the chocolate cake really worth it?'”

The Royal Society for Public Health would like to see the labelling introduced as soon as possible and says it is a move many consumers would also welcome.

It says: “This type of labelling really does put an individual’s calorie consumption in the context of energy expenditure and knowing how out of kilter we can partly explain the record levels of obesity we face.

“Small changes can make a big overall difference to calorie consumption, and ultimately weight gain.”

Daley hopes a large food chain or company will be willing to try the new labels on their products so the system can be given a ‘real-life’ trial.