An agency in the U.K. recommends food labels contain information about how much physical activity it takes to burn off the calories in certain food products.

Food labels tell you how many calories an item has as well as how much fat and sodium it contains.

So, why shouldn’t it also tell you how much exercise you’d have to do to burn off the calories you just ingested?

A health agency in the United Kingdom is proposing such an “exercise equivalent” label on food products in their country.

They call it an immediate and effective way to help consumers change their eating habits.

However, a well-known nutrition expert interviewed by Healthline said that while the proposal is a good concept, there are many potential drawbacks, including the vastly different ways different people burn calories.

“It’s good in the sense that it can raise awareness of how much it takes to burn off food, but it can’t be a ‘one size fits all’ approach,” said Kristin Kirkpatrick, M.S., R.D., L.D., a licensed, registered dietician who is a wellness manager at the Cleveland Clinic Wellness Institute.

Read More: Why Is Nutrition Advice So Confusing? »

The Royal Society for Public Health is recommending the United Kingdom introduce an “activity equivalent” as part of calorie labeling on food.

Shirley Cramer, the chief executive of the agency, said such a label would provide consumers with an “immediate link” between a food’s energy content and the physical activity it takes to work it off.

In an opinion piece in The BMJ, Cramer says the idea is crucial because two-thirds of the U.K. population is either overweight or obese.

“We desperately need innovative initiatives to change behavior at [the] population level,” she wrote.

The labels could include symbols that would show the minutes of several different physical activities that would equal the calories in a product.

For example, a person of average weight and age would need to walk 26 minutes to work off the calories contained in a can of soda.

“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,” Cramer wrote.

Cramer added that placing information on food and drink packaging to promote an active lifestyle “could be a logical solution to a multifaceted problem, and the benefits of being active go far beyond maintaining a healthy weight.”

Read More: You Can Have Your Cake and Eat It Too Under New National Guidelines »

Kirkpatrick does like the basic idea behind the U.K. proposal.

However, she said there are a number of stumbling blocks.

One of the biggest is the fact people burn calories at different rates depending on their age, gender, weight, physical condition, and even resting metabolic rate.

“There are so many factors involved in how many calories someone will burn during a 3 mile run,” said Kirkpatrick.

She said there would need to be a government-regulated standard on who the “average person” is on these labels.

Another consideration is not all food ingredients are metabolized the same. You might be able to burn off sugar calories pretty quickly, but that doesn’t mean it’s OK to eat a large amount of that ingredient.

“That is a huge component here,” said Kirkpatrick.

The dietician also worries that some people might use the exercise equivalent as an excuse to consume unhealthy food.

If they see it takes 20 minutes of walking to burn off the calories in a cookie, they might justify that food choice because they are taking a walk that evening.

Read More: Reducing Sugar in Sodas Would Greatly Reduce Obesity and Diabetes »

Another question is whether such labels would be mandatory or voluntary.

Kirkpatrick notes companies with healthier foods would probably want to post that information while companies with less healthy foods would be reluctant to do so.

Calculating the exercise equivalents probably wouldn’t be all that difficult, she said. Companies could use an algorithm based on an “average person” for different food items.

Reprinting labels, on the other hand, would be an extra cost.

“That is adding another layer,” Kirkpatrick said.

Kirkpatrick suggested the best way might be to have the exercise equivalent information as part of an online site.

A consumer could answer a few questions about weight, age, gender, and other basic personal facts and then see how much physical activity is needed to burn off certain foods.

However it’s done, Kirkpatrick said exercise equivalents should be only one part of an overall strategy.

“We need to teach people how to eat better,” she said.