From "You Are the Placebo" by Joe Dispenza:

There was a Harvard study of 84 hotel maids. They were divided into 2 groups. One group was told that they got enough exercise just doing their jobs; the other group was told nothing. After 1 month, the first group lost an average of 2 pounds, lowered the percentage of body fat, and lowered their systolic blood pressure by 10 pts. The group that was told nothing remained unchanged.

Mind-set Matters: Exercise and the Placebo Effect

This study suggests that having awareness alone can influence health.