How far would you need to run to burn off the calories in a candy bar? A recent paper asks whether providing answers to this type of question on food packaging might reduce calorie intake.

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Could a subtle change in food labeling reduce calorie intake?

Including nutritional information on food packaging can help consumers decide whether they want to buy a product.

However, according to the authors of a new review and meta-analysis, “Evidence shows that current front-of-pack nutrition information on food [and] drinks is having a limited effect on changing purchasing or eating behaviors.”

Although the numbers of calories are clearly marked on food labels, for many people, these numbers are quite meaningless.

Because obesity is so prevalent, particularly in the Western world, many researchers are looking for ways to address it.

Making changes to food labels is a relatively simple, cost effective intervention; if experts can find a way to use food labels to influence food choices, it could have a substantial impact on the weight of the population of the United States, for example.

The Journal of Epidemiology & Community Health recently published the findings of the new analysis.

One possible way to approach food labels is to explain, in real terms, what the calorie content of a product means. This approach is called physical activity calorie equivalent (PACE).

With this system, a label displays how far — or for how long — a person would need to run or walk to use up the calories in the food item.

As the authors explain, this level of detail would help consumers decide whether the added energy intake was “worth it.” Aside from the information it provides, the authors believe that PACE would also serve as a regular reminder of the importance of physical activity in daily life. They write:

When a consumer sees a visual symbol that denotes it will take 4 hours to walk off a pizza and only 15 minutes to burn off a salad, this, in theory, should create an awareness of the ‘energy cost’ of food [and] drink.”

Amanda J. Daley et al.

Some studies have already looked at the impact of PACE labeling, but to date, studies have been relatively small, and findings have been contradictory.

For instance, one review of the evidence, published in 2018, concluded that this method of labeling does not make a significant difference to the number of calories in foods that people order.

The authors of the latest paper note, however, that the earlier review included just seven studies. Since its publication, researchers have done more work on this topic, and the new review provides an up-to-date account of the evidence for and against PACE labeling.

For the new analysis, the researchers identified 15 papers that met their criteria for inclusion. All the studies were randomized, and they compared PACE food labeling with either a different type of labeling or no labeling. In total, the studies included data from 4,606 participants.

Pooling the data from 14 of the studies, the scientists identified a significant effect. They found that, when the researchers used PACE labels on food and drink items and on menus, participants selected, on average, 65 fewer calories per meal. The authors conclude:

“PACE labeling shows some promise in reducing the number of [calories] selected from menus, as well as the number of calories and the amount of food (grams) consumed by the public, relative to comparator food labeling [or] no labeling.”

The scientists estimate that, if the labeling was widely adopted, it might reduce intake by around 195 calories each day. Even small reductions in calorie intake, among a whole population, can make a significant difference.

If the U.S. population, for example, reduced individual intake by just 100 calories each day, “Obesity could be prevented,” the authors report.

One significant issue that plagues this area of research lies in the experimental setting. In the current analysis, most of the studies were performed under laboratory conditions and investigated hypothetical meal selections.

The authors call for more studies based in restaurant or supermarket settings, for instance. It is quite possible that people decide what to eat in different ways, depending on their situation. The authors write:

Future research should investigate the effects of PACE labeling in more real-life or naturalistic settings.”

Amanda J. Daley et al.

Different settings would also introduce other factors that could play a role, including price and marketing. Similarly, people might choose differently when selecting a snack, compared with a full meal — there are still many questions to answer.

In conclusion, scientists need to carry out more research to identify the true benefits of PACE, if any. Because obesity is so widespread and PACE is relatively simple to implement, the theory is well worth pursuing. Even a small dip in calorie intake could benefit society.