How do you persuade people to eat less and exercise more? We love to think it's a matter of getting them to see facts and make good decisions, because that implies that people are thoughtful and that their choices matter. But this paper, published online yesterday by the Journal of Adolescent Health, points to a more humble solution: Ignore people's thoughts and feelings, and just move the food further away.

Why don't we have more policies like that? I think it's because we're emotionally attached to a bankrupt theory of behavior. "Rational economic man" lies to us about human nature. But it's a flattering lie, and we cling to it. Behavioral research says that even in important decisions, we're unaware of our own motives, indifferent to facts, and governed by a mix of trivial accidents and psychic rules we don't know we are following. Rational economic man says we're self-aware, informed, consistent and logical—cool appraisers of our own best interests. Who wouldn't rather hear that?

Trouble is, self-flattery is the enemy of self-management: If you think you can quit smoking by deciding to, or that you'll stick to a diet just because you're clear on the benefits of weight loss, then you won't recognize, or cope with, the effects of advertising, marketing, social networks and other irrational forces. If you imagine that your behavior is decided by the complicated to-ing and fro-ing of your conscious mind, you will feel important, for sure. But—as Alcoholics Anonymous and other addiction programs have long maintained—you'll have more success changing yourself if you admit you're simpler and dumber than your conscious mind wants to believe.

The new paper I mentioned is a case in point. It suggests a very simple and quite unflattering method for preventing weight gain in college freshmen: Just don't put a cafeteria in their dorm.

Kandice Kapinos and Olga Yakusheva tracked 388 first-year students at Marquette University in Wisconsin. In four of the seven different dormitories in which they were living, there was a dining hall that served three meals a day. Students in the other three had to go outside to eat. Over the course of their freshman year, men in the dining-hall equipped dorms ate an average of one and a half meals more each week than did their counterparts in the foodless dorms, and averaged almost three more snacks per week too. Women in the dormitories with food service ended the year weighing nearly two pounds more, on average, than their peers in the other buildings. They also exercised less.

If you dismiss this data as obvious or trivial, you have, I think, fallen for the flattering wiles of rational economic man. He invites you to think obesity is a problem to be combatted with facts and figures; that dignified, autonomous individuals need to be persuaded to lay off the cookies and get to the gym. How undignified and dull, by contrast, is the thought that people's thoughts and convictions can be ignored—that you can help them avoid obesity just be putting the food outside. Yet in this case, at least, flattering ourselves less might help us control ourselves more.

Kapinos, K., & Yakusheva, O. (2010). Environmental Influences on Young Adult Weight Gain: Evidence From a Natural Experiment Journal of Adolescent Health DOI: 10.1016/j.jadohealth.2010.05.021