Fast food restaurants have pointed to the new, healthier items on their menus. And a few years ago, skeptics found the some of the salads contained more calories and fat than burgers in the same establishments.

But suppose that they are offering really healthy salads now. What if, in giving people a choice, these dishes really push diners toward the unhealthiest alternatives? That's called "vicarious goal fulfillment," and it's what Gavan Fitzsimons of Duke University and his coauthors found in a recently published laboratory experiment. Subjects were more likely to pick a really unhealthy item from the menu when a side salad was offered as an option. The researchers explain:

Just because we consumers want to see healthier items available does not mean that we are going to choose them. 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.

People with the highest levels of self-control actually are more likely to choose unhealthy foods in the presence of healthy ones than those with low self-control.

The only real solution I can see is to favor establishments that offer only healthy food. But given our supposed zest for better eating, why aren't there more of them? I'll have to think that question over and report later.