Restaurants aren’t doing Americans many favors when it comes to nutrition. According to a new analysis of U.S. restaurant-going habits, most meals people eat out are of poor nutritional quality. This is critical to people’s health, since restaurant food is the source of one in five calories Americans eat.

Researchers at the Friedman School of Nutrition Science and Policy at Tufts University analyzed the dietary habits of more than 35,000 U.S. adults who participated in the National Health and Nutrition Examination Survey between 2003 and 2016. The study cohort members had all eaten out at full-service (meaning with waitstaff) restaurants, fast-food establishments or fast-casual restaurants such as Chipotle and Panera.

To analyze the nutritional quality of those meals, the study authors looked to the American Heart Association 2020 diet score.

Publishing their findings in The Journal of Nutrition, the investigators found that 70% of the fast-food meals Americans ate were of poor dietary quality in 2015 to 2016, a slight decline from a rate of 75% seen in 2003 to 2004. About half of meals at full-service restaurants were of poor nutritional quality, a rate that held stable during the study period. All other restaurants provided meals of intermediate quality.

Virtually none of the restaurant meals consumed—0.1%—were of ideal quality.

“Our findings show dining out is a recipe for unhealthy eating most of the time,” Dariush Mozaffarian, MD, PhD, MPH, senior author and dean of the Friedman School, said in a press release. “It should be a priority to improve the nutritional quality of both full-service and fast-food restaurant meals, while reducing disparities so that all Americans can enjoy the pleasure and convenience of a meal out that is also good for them.”

Looking at trends based on the race of the survey respondents, Mozaffarian and his colleagues found that the restaurant food whites and Mexican Americans consumed improved in nutritional quality during the study period, while the quality of restaurant food African Americans ate did not.

Of all calories Americans eat, 21% come from restaurants, including 9% from full-service restaurants and 12% from fast-food restaurants.

“We found the largest opportunities for enhancing nutritional quality would be adding more whole grains, nuts and legumes, fish, and fruits and vegetables to meals while reducing salt,” said the study’s first author Junxiu Liu, PhD, a postdoctoral scholar at the Friedman School. She noted the study findings showed no improvement in sodium levels in fast-food meals and worsening levels in full-service dishes consumed.

“Our food is the number one cause of poor health in the country, representing a tremendous opportunity to reduce diet-related illness and associated health care spending,” Mozaffarian said.  “At restaurants, two forces are at play: What’s available on the menu and what Americans are actually selecting. Efforts from the restaurant industry, consumers, advocacy groups and governments should focus on both these areas.”

To read a press release about the study, click here.

To read the study abstract, click here.