More restaurants and vending machines offer healthy choices these days, so why do Americans' waistlines continue to expand? A new study in the Journal of Consumer Research shows that some efforts to control eating may backfire.

Just seeing a salad on the menu seems to push some consumers to make a less healthy meal choice, according to a Duke University researcher.

It's an effect called "vicarious goal fulfillment," in which a person can feel a goal has been met if they have taken some small action, like considering the salad without ordering it, said Gavan Fitzsimons, professor of marketing and psychology at Duke's Fuqua School of Business, who led the research.

Consumers may feel they have fulfilled a healthy eating goal even if they choose an unhealthy food, and the presence of a healthy option among food choices may draw their attention to the least-healthy choice available, according to authors Keith Wilcox (City University of New York), Beth Vallen (Loyola College), Lauren Block (City University of New York), and Gavan J. Fitzsimons (Duke University).

"Just because we consumers want to see healthier items available does not mean that we are going to choose them," write the authors. "We present evidence that for many consumers, the addition of healthy alternatives to food choice sets can, ironically, increase the consumption of very indulgent food items."

In a series of four studies, the researchers examined how consumers' food choices differed when a healthy item was included in a set compared to when it was not available. The study results showed that the mere presence of a healthy item vicariously fulfills health-related eating goals, drives attention to the least-healthy choice, and provides people with license to indulge in tempting foods. They also demonstrated that these effects were more pronounced in people with relatively high levels of self-control.

In one study, participants chose from a menu that included French fries, chicken nuggets, and a baked potato or these items plus a side salad. After being told that each item cost the same amount of money, respondents were instructed to choose a side dish for their lunch. "As we predicted, when given the choice of fries, chicken nuggets, or a baked potato, people high in self-control rarely chose the fries, which are considered the least-healthy option in the set. However, add the salad to the set and what happens? High self-control individuals were significantly more likely to choose the French fries." The authors found the opposite was true for people with low self-control.