New research suggests that campaigns to promote exercise may have an unintended consequence: they make people eat more.

In a study in the March issue of the journal Obesity, 53 college students were asked to judge a series of posters from an exercise campaign and, on another occasion, a group of similar-looking posters that did not mention exercise. They were told they would be given a few raisins afterward, which they were to taste and rate. After the students looked at the exercise posters, they ate an average of 18 calories, but they ate only 12 calories after viewing the posters with no mention of exercise.

In a second test, 51 different students, told they were participating in a computerized test of hand-eye coordination, were randomly assigned to be exposed to action words like “active” and “go” typically used in exercise advertising. A control group was exposed to neutral words like “pear” or “moon.” Again, they were offered food (peanuts, raisins and M&M’s this time), and the results were similar: those who had heard the action words ate more.

Dolores Albarracin, the lead author and a professor of psychology at the University of Illinois, said that context was important. “When the setting of the advertising is more conducive to eating than exercise, people eat,” she said. “If you just wallpaper everyplace with these kinds of posters, it may not do much good.”