Fancy your supermarket receipt assessing the healthiness of your trolley? Well, a new proposal says the “traffic lights” system – widely adopted on food and drink packaging since 2013 – should be migrated from individual items to entire receipts. Forget the problem of making it through checkout without impulse-buying three bags of bonbons and a copy of Heat! magazine; now it is about the half-price pizza catapulting your basket into “red” territory.

“Instinctively, it seems like a good idea,” says Ed Morrow, campaigns manager at the Royal Society for Public Health. “If health information is just on the product, it’s easy to ignore, but if you get another reminder at the till you might start to compare receipts, see what you’ve scored each time, then try to do better. Doing things that gamify the experience of shopping can be a good motivator in terms of changing behaviour.” That is if you want your midweek trip to Tesco to be gamified: is this just 21st-century code for the nanny state? “It’s not telling people what to do,” Morrow says. “All it does is provide people with extra information.”

According to Matthew Cole – a health expert who is working alongside the man behind the idea, creative designer Hayden Peek – receipts are a reliable indicator of a person’s dietary habits over time and, like labelling in supermarkets and on menus, could help us make healthier choices. But does such labelling really work? Research shows that consumers spend only six seconds looking at a product before buying it and can find labels confusing due to information overload. Meanwhile, obesity levels continue to rise: according to Public Health England, nearly two-thirds of adults were overweight or obese in 2015.

“Labelling is not the solution to the obesity crisis,” says Anna Taylor, executive director at the Food Foundation. “But what’s important about the traffic lights system is it encourages businesses to reformulate because they don’t want to have a product with lots of reds.” As Morrow puts it, whether or not it makes people eat more healthily, “it’s still important to have the information in terms of consumer rights. The traffic light system is a massive improvement because it’s accessible to everyone, not just those who are nutritionally literate.”

“What would be really interesting is if the retailers link it to algorithms set up for loyalty cards for those who want it,” says Taylor. “So, if a till receipt shows lots of reds, you might get vouchers to buy more veg. That’s when it could start to get really powerful. But let’s be clear: the whole food system has to work harder to make the easiest choices the healthy choices. That’s what needs to change.”