Now try the reverse. You've been good, but the scale says you've gained five pounds. Same buffet: Do you diet, or give up and eat your fill?
The department of psychology at the University of Toronto was actually mean enough to play this mind game with a group of diligent dieters.
As reported in The Journal of Abnormal Psychology, the people who were told they had lost an additional five pounds maintained their self-restraint at the buffet. But those who thought they'd gained five pounds "reported lower self-esteem, less positive moods, and more negative moods." Led to the buffet, they ate as if dieting just didn't matter anymore.