Nagging works, according to Canadian researchers who found that e-mail spam messages influence people to take better care of themselves. The study involved more than 1,600 volunteers at five workplaces who were participating in a larger study on exercise and health. The researchers sent participants e-mail messages about exercise and health every week for 12 weeks. Other volunteers didn't receive the messages.

People who received the messages exercised more, reduced their average body mass index, and knew more about the benefits of exercise and diet modifications than those who didn't get the messages. Some people who didn't get the messages even gained weight during the study.

Source