‘I’ll Have the Cake.’ The Music Made Me Do It.

Trendy restaurants that amp up the music generate mixed feelings in diners, attracting some and repelling others. Now there’s evidence that loud background music affects patrons’ food choices — and not in a good way.

Behavioral scientists who ran a series of lab studies and real-life field experiments found participants selected more unhealthful or calorie-laden items like red meat and cake when the ambient music was loud, and were more likely to choose healthful items when softer music was played in the background.

The genre of music did not appear to influence the choices, the researchers said: They found the same effects whether the background music was classical; a mix of pop, rock, soul, R&B and alternative music; or heavy metal.

“High-volume music is more exciting and makes you physically more excited, less inhibited and more likely to choose something indulgent,” said Dipayan Biswas, a professor of business and of marketing at University of South Florida in Tampa and lead author of the paper, published in the Journal of the Academy of Marketing Science. “Low music makes us more relaxed and more mindful, and more likely to go for the things that are good for us in the long run.”

One field study in Sweden, conducted in a cafe in Stockholm, played the same playlist at 55 decibels (typical restaurant conversation) on one weekday and at 70 decibels (the level of a vacuum cleaner) on another weekday. When the volume was high, 52 percent of the orders were unhealthful, and only 25 percent were considered healthful. When the music was low, only 42 percent of orders were for unhealthful food, and 31 percent of food items were deemed healthful (some food and beverages were considered neutral).

Loud background music in a supermarket similarly nudged customers toward less healthful purchases, compared with softer music.

In a lab experiment, students were exposed to loud or soft classical music and then asked to choose between fruit salad or chocolate cake. When the music was high, 56 percent chose fruit salad; when the volume was low, 86 percent chose the fruit salad.

Dr. Biswas, whose earlier research found that patrons are more likely to order healthful items when restaurants are brightly lit and more likely to indulge in dimly lit restaurants, said the findings can help consumers be aware of unconscious factors affecting their choices. “It’s not entirely a conscious decision to order something that’s high calorie,” he said. “Sometimes, when the music is loud, you just go for the chips.”