By Robert Preidt
THURSDAY, Oct. 31, 2019 (HealthDay News) -- Calorie labels in fast-food restaurants appear to help customer trim purchases, but only up to a point, a new study says.
Customers ate slightly fewer calories after a fast-food chain started including calories on its menus, but the impact weakened over time, researchers found.
"Our findings suggest that calorie labeling may be most effective as a short-term strategy for reducing calorie purchases, but that other nutrition interventions may be necessary for long-term positive dietary changes in these settings," said study lead author Joshua Petimar. He's a research fellow at the Harvard Pilgrim Health Care Institute and Harvard Medical School.
In May 2018, calorie labeling on menus became mandatory for chains with 20 or more outlets in the United States. The goal was to help customers make healthier food choices.
However, effectiveness of this approach is unclear. Some studies have found associations between calorie labeling and calorie consumption, but most have been too small to identify differences before and after the introduction of calorie labeling on menus.
This new study is one of the largest to examine the issue, according to the researchers.
They assessed the impact of calorie labeling on food purchases by analyzing three years of sales data from a franchise of fast-food restaurants in the southern United States.
The franchise began providing calorie information on its menus in 2017. The researchers examined data from 2015-2018, ending up with information on nearly 50 million sales in the two years before and one year after the introduction of calorie labeling.
There was an initial decrease of 60 calories per sale (about 4%) after calorie labeling began, but that was followed by a slight weekly increase over the next year, according to the study.
"We recommend future research to estimate the effects of calorie labeling over a longer period, particularly once restaurants have had time to reformulate their menus," Petimar said in an institute news release.
The study results are in the Nov. 2 issue of the BMJ.