Packaging should not only provide nutritional information but should “also help people to change behaviour,” said Shirley Cramer, chief executive of the Royal Society of Public Health.
There is “little evidence” that traffic light labelling actually changes behaviour, she said.
In a personal view, published in The BMJ, Ms Cramer said food and drinks should be labelled with “activity equivalent” calorie information.
This should include how much time people could spend doing various different exercises that are “equivalent in the calories expended to those in the product”, she said.
Such information would help people to choose healthier products, eat smaller portions or do more exercise.
“The aim is to prompt people to be more mindful of the energy they consume and how these calories relate to activities in their everyday lives, to encourage them to be more physically active,” she wrote.
She points to research which found that 44 per cent of people find current front-of-pack information confusing.
“Such information needs to be as simple as possible so that the public can easily decide what to buy and consume in the average six seconds people spend looking at food before buying,” she added.
“People find symbols much easier to understand than numerical information, and activity equivalent calorie labels are easy to understand.
“For example, the calories in a can of fizzy drink take a person of average age and weight about 26 minutes to walk off.”
In a separate study, scientists revealed this week that children are eating too many calories and too much salt and missing out on key vitamins. High intake of protein and too many calories overall puts youngsters at risk of obesity, while too much salt could put them at risk of high blood pressure and strokes in later life.
Researchers urged parents to follow government guidelines on giving children up to the age of five supplements to boost levels of iron and vitamin D, after their study found youngsters were woefully lacking in essential vitamins.
The study, published in the British Journal of Nutrition, examined data for 2,336 children from one of the UK’s largest dietary datasets for toddlers, the Gemini twin birth cohort. Last year the Royal Society for Public Health (RSPH) suggested that drinks companies should label their alcoholic products to show the number of calories they contain as part of a bid to tackle obesity
In a paper on the “invisible” calories in alcohol, the organisation called for calorie counts to be included alongside the number of units, daily guidelines advice and pregnancy warnings, which drinks companies agreed to include on their packaging as part of a deal with the government in 2011.
The move was backed by Alcohol Concern but drinks producers said the laws required could take years and people should be more focused on alcohol content.