Stuart Flint, an associate professor of the psychology of obesity at Leeds University and a director of Obesity UK, which supports overweight people, said it was unclear who the new rules would help.

“It might not be helpful,” he said. “We need to really understand how people are going to engage with this. Is it going to mean that people only look at calories? A chocolate bar is less than a balanced meal, but we don’t want people to be having a chocolate bar and skipping the meal. It’s not always about reducing the amount we eat.”

Gregg Wallace, the presenter of MasterChef and founder of weight-loss website ShowMe.Fit, is more optimistic that it could make a difference. “Any information or understanding of calorie content in our food – whether in takeaway menus or in restaurants – is a great idea,” he said. “What we can measure, we can manage – and this is another step towards enabling people to make more educated choices.”