More than just sugar ...

... Why Placebos Work Wonders - WSJ.com.

Hotel-room attendants who were told they were getting a good workout at their jobs showed a significant decrease in weight, blood pressure and body fat after four weeks, in a study published in Psychological Science in 2007 and conducted by Alia Crum, a Yale graduate student, and Ellen Langer, a professor in the psychology department at Harvard. Employees who did the same work but weren't told about exercise showed no change in weight. Neither group reported changes in physical activity or diet.