"Exercise advice on food labels could help to tackle the obesity crisis," The Guardian reports. Labelling on packaged food has to include information such as the number of calories and grams of fat. However, there's evidence that many people do not know what these measures mean.
Researchers involved in a new study have suggested converting calories into the amount of exercise needed to burn them off – for example, labels explaining that you would need to run for:
- 13 minutes after drinking a 330ml can of fizzy drink
- 22 minutes after eating a standard size chocolate bar
- 42 minutes after eating a shop-bought chicken and bacon sandwich
They hoped that doing this would encourage people to choose less calorific foods or eat less of them.
This study summarised the results of previous trials of exercise labelling (called PACE, for physical activity calorie equivalent) compared to no labelling or other nutritional labelling.
Overall, the summary found people selected less calories and ate less calories when their food choice included PACE labelling. However, the results varied a lot between studies and some of the methods used were unclear, meaning we have to be cautious about accepting the results.
Use the NHS website calorie counter to see how many calories are in your favourite drinks and snacks.
Where did the story come from?
The study was carried out by researchers from Loughborough University, Birmingham Community Healthcare NHS Foundation Trust and the University of Birmingham. It was funded by Loughborough University and the National Institute of Health Research and published in the peer-reviewed BMJ Journal of Epidemiology & Community Health on an open-access basis, so it's free to read online.
The study was widely covered in the UK media. Some overstated the effects of the labelling, or said it was only for junk food (as in the Daily Mirror headline).
The Guardian gave a balanced report, which included the point that calories are not the only nutritional information needed to make an informed choice about which food to eat.
Mail Online said that the inclusion of exercise information "shames people" into choosing less calorific food, although "shaming" was not the purpose of the studies, and there's no evidence that shame is in any way helpful for people wishing to lose weight.
What kind of research was this?
This was a systematic review of randomised and experimental studies. A systematic review is the best way to get an overview of the state of research of any topic. However, the results of a systematic review are only as good as the trials that it summarises.
What did the research involve?
Researchers found 15 eligible trials. They were a mixture of trials that compared consumer behaviour when presented with PACE-labelled food compared with food either not labelled or labelled with different information. Researchers looked at the effect of PACE labelling on:
- food or drink purchased
- food or drink selected
- food or drink consumed
They carried out a meta-analysis to pool the results and presented them as the mean difference in calories between PACE-labelled and other food chosen.
The researchers also looked at the possible risk of bias in the studies, how well they were run, and whether there was much difference between study results.
What were the basic results?
- people were less likely to buy a sugary soft drink if it was labelled with PACE information, compared to no label
- people selected on average 64.9 fewer calories if food or drink was PACE labelled, compared to no label or other labelling (95% confidence interval (CI) -103.2 to -26.6)
- people ate on average 80.4 fewer calories if food or drink was PACE labelled, compared to no label or other labelling (95% CI -136.7 to -24.2)
The researchers calculate that over the course of a day, this could result in people consuming 195 fewer calories.
The results were strongest for studies comparing PACE labelling to no labelling. When compared directly to other labelling (such as calorie-only labels or labels showing the proportion of recommended daily intake) PACE labelling made little difference.
How did the researchers interpret the results?
The researchers said: "PACE food labelling may reduce the number of calories selected from menus and decrease the number of calories/grams of food consumed by the public, compared with other types of food labelling/no labelling."
They added: "The findings emphasise the potential of easily understood food labels to reduce the calorie intake of the population by facilitating increased selection of lower calorie foods and decreased selection of higher calorie ones."
Most people become overweight or obese by consuming a few more calories every day than they burn off in daily activities. It sounds logical that people might think twice if they were aware of how much exercise is needed to burn off different types of food. But while this study suggests PACE labelling may help, the study is not conclusive.
Comparing PACE labelling with other types of labelling did not show conclusively that PACE labelling worked best, although it was better than no labelling. There were also problems with the studies included, which makes the overall results difficult to rely on. Methods of allocating people to PACE or other labelled foods was unclear in most studies, and there were wide variations between study results.
Most of the studies were carried out in laboratory conditions, rather than in restaurants, shops or cafes where people make real-world choices. That means the effect of prices and marketing were not taken into account. There's also the likelihood that people would get used to seeing PACE labels if they were introduced, and perhaps take less notice of them over time. PACE labels are only able to give an estimate of the number of calories that would be burnt by someone of an average weight performing each exercise, but this is highly variable. It depends on factors such as exercise intensity and a person's build.
It's also important to remember that we need calories just to keep our bodies working. The recommended daily intake is around 2,000 calories for an average woman and 2,500 for an average man. While it's important to be active and exercise, it's not necessary to exercise to burn off all the calories from the food you eat.
Additionally, calories are not the only nutritional aspect to consider. For example, a small bag of sweets might have less calories than a chicken and salad sandwich, but the nutrients from the sweets would not be as useful as those from the chicken and salad.
While PACE labelling might be an extra tool to help people consider making better food choices, it's not the full answer to a healthy diet and is unlikely to singlehandedly tackle the UK's obesity epidemic.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Guardian, 10 December 2019
BBC News, 11 December 2019
Mail Online, 10 December 2019
Sky News, 11 December 2019
Daily Mirror, 10 December 2019
The Sun, 10 December 2019
The Daily Telegraph, 10 December 2019
The Times (subscription required), 11 December 2019
Links to the science
Journal of Epidemiology & Community Health. Published online 10 December 2019