Labelling the number of calories in fast food restaurant meals can be linked to a “small” reduction in the amount customers purchase, a new study claims.
Researchers at Harvard evaluated the impact of calorie labelling on meals from a large restaurant franchise in the southern United States, where obesity rates are among the highest in the country.
They found that while labelling can be linked to a “small immediate” decrease in the average number of calories purchased, it was followed by a gradual weekly increase over the following year.
The study, which was published in the BMJ on Wednesday, said: “These results imply that calorie labelling alone may not be enough to make sustainable reductions in calorie intake in fast food restaurants.”
Large chain restaurants in the US have been required to label the calorie content of individual dishes since May 2018 to help customers make healthier choices.
A similar policy is being considered in the UK.
US researchers were provided with weekly sales data from 104 restaurants during a two-year period before labelling was introduced and one year afterwards.
The restaurant franchise labelled its menus ahead of the new rule being introduced in the US.
It gave researchers access to nearly 50 million transactions across a three-year period between April 2015 and April 2018.
They found that calorie labelling was associated with an immediate decrease of 60 calories per transaction.
The study said the reduction might have been “largely driven” by customers purchasing fewer items, rather than lower calorie items.
But the decrease was followed by a weekly increase of 0.71 calories per transaction over the next year, the study said.
This meant that by the end of the study, the 60 calorie reduction had dropped to just 23 fewer calories for each purchase made.
In a linked editorial, researchers from the University of Oxford said: “Although the results of this study might be disappointing to some, small changes to calorie intake can have meaningful effects at the population level.
“Obesity is complex, and it is only through taking a multifaceted, cross-government approach that it can be tackled — an approach in which calorie and nutrition labelling on restaurant menus should play a part.”