Daily exercise makes sedentary women more energetic and happier, according to research presented in March 2008. “Small changes—like walking just 10 minutes a day—lead to big changes because motivation follows action,” says the study’s principal investigator, Timothy Church, director of preventive medicine research at Louisiana State University and author of Move Yourself.

And you don’t have to push yourself to the limit: a University of Georgia study confirmed that a regular low-intensity workout, even a leisurely stroll, boosted energy levels by 20 percent and decreased fatigue by 65 percent.