Merely thinking about getting a salad instead of french fries can satisfy intentions to eat healthily, ironically making it easier to go ahead and order fries after all, new research shows.

In a series of experiments, researchers found that people were substantially more likely to choose the least-healthy option on a menu, such as a cheese burger or ice cream, when the menu included a single more virtuous option, such as a veggie burger or fruit.

"Because the healthy option is there, it somehow satisfies this healthy eating goal in them and then they felt liberated to sort of go crazy and choose something really, really bad for them," Dr. Gavan J. Fitzsimons of Duke University in Durham, North Carolina, who led the study, explained in an interview with Reuters Health.

Fitzsimons and his team were investigating something they call "vicarious goal fulfillment," in which having the opportunity to act in a way that fulfills long-term objectives — for example, eating healthier — fulfills a person's goal, even if he or she doesn't actually make that healthier choice. They hypothesized that people would choose the worst option on a menu more frequently when that menu included a food that represented a healthy goal, compared to when they were presented with a menu that included a range of less-healthy options.

In every one of the experiments Fitzsimons and his colleagues did, this turned out to be true.

Among 70 undergraduate students, for example, 37% chose a bacon-cheeseburger when the alternatives included a veggie burger (other options were a chicken or fish sandwich). But when the veggie burger wasn't on the menu, just 17% picked the bacon cheeseburger.

Similar patterns were seen when salad was included with french fries, chicken nuggets, and baked potato (more people chose fries) and when people were offered 100-calories worth of Oreo cookies along with original Oreos, chocolate covered Oreos, and golden Oreos (more picked the chocolate-covered cookies).

Furthermore, people with high levels of self-control were actually more likely to make indulgent choices when offered a healthy option than people who didn't keep such a tight rein on themselves. Further experiments demonstrated that more restrained people indeed unconsciously acted as if they had fulfilled their health goals by considering a healthy choice.

Getting people to eat better requires more than just adding a healthy option or two to the menu, be it at fast food restaurants or school cafeterias, according to Fitzsimons. People should stay away from fast food joints if they really want to keep eating healthily, he added, while schools should toss unhealthy choices off cafeteria menus entirely rather than trying to tempt kids away from pizza with a couple of vegetable offerings.

By offering a couple of nutritious choices, the researcher said, fast food restaurants may tempt health-conscious consumers with the possibility that they might pick these items. Still, junk food purveyors are seeing their profits grow, he added. "It's not from salads."