Don't automatically delete that weight-loss junk mail - it could actually help you slim, according to a new study in the American Journal of Preventive Medicine.

A 16-week study of nearly 800 employees of health care firm Kaiser Permanente found that merely receiving emails containing health and lifestyle advice could change the behaviour of even confirmed layabouts.

The messages to participants suggested small, practical, individually tailored goals, such as eating fruit for a snack three times a week, walking for 10 minutes a day at lunch time, or walking to the shops instead of driving.

More junk mail, less junk food

At the end of the trial, the recipients of the emails were more physically active, eating more fruits and vegetables, and reducing their intake of saturated fats and trans fats, compared to a control group.

The biggest changes occurred among people who were not regularly active before receiving the email. These users increased moderate physical activities by almost an hour a week and decreased the amount of time they spent in sedentary activities, like watching TV, by about two hours a week. The changes had a lasting effect four months after the intervention ended, the study found.

Study lead investigator Dr Barbara Sternfeld said, "An e-mail programme includes all the things that behavioral scientists have said for years about changing behavior: small goals tailored for the individual, reinforcement, and tracking but delivered in a mass, cost-effective way."

Another paper published in January in the Journal of Medical Internet Research found that a similar e-mail program reduced 'presenteeism' among the trial participants and could even reduce bodily pain.