Are labels that tell you how long it takes to burn food off helpful or misleading?

When you examine a box of muesli bars or a packet of chips, deciphering what the 13 grams of sugar or 144 calories listed on the back mean in practical, real-world terms can be challenging.

What if that label informed you it would take precisely half an hour of vigorous bike riding or an hour-long walk to “burn off” the calories inside? The prospect of exercise is a little harder to look past — and a UK health expert believes this is what it’ll take for people to make healthier choices.

Writing for the British Medical Journal, Shirley Cramer argues that labelling food and drinks with their physical activity equivalents — illustrated by simple icons — could be a “logical solution” in the effort to reduce obesity.

“The objective is to prompt people to be more mindful of the energy they consume and how these calories relate to activities in their everyday lives, and to encourage them to be more physically active,” the Royal Society of Public Health’s chief executive writes.

Would 'activity equivalent' labels change your eating? Image: iStock

"We won’t reduce obesity by focusing on diet or physical activity alone. People need to create a balanced relationship between the calories they consume and the calories they expend."

This isn't a completely new concept; we've all seen those articles and infographics detailing how many minutes of gym time a Mars bar or burger earns you ('Here, enjoy your treat with a side of self-loathing!').

According to Caitlin Rabel, Accredited Practicing Dietitian and Accredited Nutritionist with Bites for Health, Cramer's labelling proposal certainly has some merit.

"I think the intentions behind this strategy are good, as some people have no idea how energy-dense some foods — especially fast foods — are," she explains.

Watch: How much sugar is in your favourite drink? (Post continues after video.)

This is an important consideration, especially as many of the foods we typically view as 'healthy' (smoothies and fro-yo, anyone?) have been shown to be loaded with kilojoules. Knowledge is power.

Activity equivalents could also make food labels less baffling than they currently are, at least where energy intake is concerned. As Shirley Cramer notes in the BMJ, public polling in the UK has found 44 per cent of people find current front-of-packet information confusing.

However, Rabel also believes this approach could be misleading.

For one thing, the human body naturally uses much of the energy from food and drinks through its various processes, which include breathing, digestion and circulation. In other words, living.

"The amount of calories each person burns just by being alive is called their Basal Metabolic Rate (BMR), which covers all of the processes [that] keep the body functioning properly," Rabel explains.

Yes, exercise burns energy - but so do your body's natural processes. (Image: iStock)

That's not to say you can eat seven kilos of bacon a day and just expect your body to deal with it, but exercise isn't the only means by which calories are expended.

BMR differs from one person to the next, and while medical professionals use a few equations to estimate individual numbers, Rabel says these aren't necessarily accurate.

Similarly, each and every one of us will burn calories at different rates through exercise — our height, weight, genetics, sex and body composition all come into play — so it's difficult to provide an accurate, one-size-fits-all recommendation.

Then there's the factor of how much of our food we should be advised to expend. Physical activity equivalents in labels and articles work on the premise that we need to burn every single calorie, yet Rabel says this "definitely" isn't the reality.

"It is unfeasible for people to try and do so. Counting calories is most often not effective for weight loss or maintenance, and often leads to gain of weight," she says. (Post continues after gallery.)

"It can often also be a form of disordered eating if people cannot enjoy food in a social situation and are focused purely on calories."

This is where food labels with activity equivalents verge on being potentially dangerous, not just mildly guilt trip-py or even misleading.

"The view of X food= X amount of exercise is oversimplified, and could be very detrimental for those struggling with poor body image and disordered eating," Rabel argues.

"I question whether it will actually cause people to rethink their food choices, or just create a cycle of guilt for not 'burning off the food' they have eaten."

What do you think - should food labels come with physical activity equivalents?