Lean Teens

Teen study finds exercise has to be vigorous to offset effects of modern life

A new study indicates that today's teenagers really need to exercise if they want to lose weight -- and a mild workout may not be enough.

The Medical College of Georgia study found the fittest students got high amounts of moderate and vigorous activity. But the leanest teens -- with the lowest percentage of body fat -- were only those getting the most strenous workouts. Researchers say the added intensity may be needed to overcome the effects of today's sedentary lifestyles.

One obesity expert said the teens may need to "make up" their exercise deficit to avoid becoming overweight. The study tracked more than 400 students ages 14 to 18. Over five days, the group was tested for cardio fitness with a treadmill, and their body fat was measured.

The results are published in this month's American Journal of Clinical Nutrition.