Another argument for mind over matter, and support for the placebo effect.
" Harvard University psychologist Ellen Langer and her student Alia Crum found that many of the beneficial results of exercise are due to the placebo effect.
The researchers studied 84 female housekeepers from seven hotels. Women in 4 hotels were told that their regular work was enough exercise to meet the requirements for a healthy, active lifestyle, whereas the women in the other three hotels were told nothing. To determine if the placebo effect plays a role in the benefits of exercise, the researchers investigated whether subjects' mind-set (in this case, their perceived levels of exercise) could inhibit or enhance the health benefits of exercise independent of any actual exercise.
Four weeks later, the researchers returned to assess any changes in the women's health. They found that the women in the informed group had lost an average of 2 pounds, lowered their blood pressure by almost 10 percent, and were significantly healthier as measured by body-fat percentage, body mass index, and waist-to-hip ratio. These changes were significantly higher than those reported in the control group and were especially remarkable given the time period of only four weeks. "