Labelling menus with the calorie content of individual dishes and drinks in fast food outlets is associated with a small immediate decrease in average calories purchased, according to a study published by the BMJ. However, over the next year there was a gradual weekly increase in calories per transaction, implying that calorie labelling alone may not be enough to make sustainable reductions in calorie intake in fast food restaurants.
Large chain restaurants in the United States have been required to provide calorie labelling since May 2018. The policy is being considered in the United Kingdom, but evidence of its effects on calorie purchases is mixed and incomplete.
A team of US researchers evaluated the impact of calorie labelling on calories in meals bought in a large restaurant franchise in the southern US, where obesity rates are among the highest in the country.
The franchise labelled all menus with calories in April 2017 and provided weekly sales data from 104 restaurants for two years before calorie labelling was introduced (April 2015 to April 2017) and for one year after its introduction (April 2017 to April 2018).
The researchers analysed nearly 50 million transactions across three years. They grouped items into one of five categories: entrees/main courses, sides including desserts, sugar sweetened beverages, low calorie beverages, and condiments and calculated total calories for each menu item.
After adjusting for the baseline trend, season and holidays, calorie labelling was associated with an immediate decrease of 60 calories per transaction, or 4% of total calories purchased.
However, the initial decrease was followed by a small weekly increase in calories per transaction over the next year so that, by the end of the study, the 60-calorie reduction had dropped to just 23 fewer calories for each purchase made.
Limitations of the study include the inability to calculate calories purchased per person or to measure meal modification (such as adding condiments), beverage refills, or how much of each meal was eaten.
The authors concluded that future research was needed to estimate the effects of labelling over a longer period, especially once restaurants had reformulated their menus, to understand the overall effectiveness of calorie labelling as a nutrition policy.
In a linked editorial, Dr Adam Briggs and Dr Asha Kaur said that the paper contains other important messages for decision makers. The data showed that the impact of calorie menu labelling is greater in areas that are less socioeconomically deprived and may inadvertently increase health inequalities. Also, restaurants may reformulate dishes to have fewer calories but more unhealthy nutrients such as salt or sugar. Including additional nutritional information on labels might help reduce the impact of such negative outcomes.
Although these results might be disappointing to some, they noted that small changes to calorie intake can have meaningful effects at the population level and called for a multifaceted, cross government approach to tackle obesity in which calorie and nutrition labelling on restaurant menus play a part.