TUESDAY, June 25 (HealthDay News) -- Only half of American youths get the recommended amount of exercise and less than one-third eat the suggested amount of fruits and vegetables each day, according to a federal government study.

Researchers surveyed nearly 10,000 students aged 11 to 16 in 39 states, and found that only half were physically active five or more days a week and fewer than one in three ate fruits and vegetables daily.

"The students showed a surprising variability in eating patterns," study author Ronald Iannotti, of the prevention research branch of the U.S. National Institute of Child Health and Human Development, said in an institute news release. "But most -- about 74 percent -- did not have a healthy pattern."

The students in the study also were asked to describe their body image, emotional health and general satisfaction with life. The researchers classified the participants' diet and exercise habits into three general categories: unhealthful (26 percent), healthful (27 percent) and typical (47 percent).

Youth in the typical group were least likely to exercise five or more days a week or to eat fruits and vegetables at least once a day. They were more likely to spend time watching television, playing video games or on a computer than those in the healthful group, but less likely to do so than those in the unhealthful group.

The participants in the typical group infrequently ate fruits and vegetables, but also infrequently consumed sweets, chips, french fries or soft drinks. They were more likely than those in the other two groups to be overweight or obese and to be unhappy with the appearance of their bodies.

Youth in the unhealthful group consumed the most sweets, chips, french fries and soft drinks, and also were more likely than the other groups to watch TV, play video games and use a computer more than two hours a day, according to the study, which was published in the Journal of Adolescent Health.

Despite the unhealthy foods they consumed, youth in the unhealthful group were more likely to be underweight and to report needing to put on weight. Youth in this group also were more likely to report symptoms of depression and poor physical health, such as backaches, stomachaches, headaches or feeling dizzy.

Nearly 65 percent of students in the healthful group exercised five or more days per week -- the highest rate of the three groups. They were least likely to spend time in front of a screen, most likely to report eating fruits and vegetables at least once a day, and least likely to consume sweets, soft drinks, chips and french fries. They had the lowest rates of depressive symptoms and the highest life satisfaction ratings.

All three groups could stand to improve their health habits, Iannotti said, whether by walking or biking between home and school or eating more fresh produce each day.

Children and teens should get one hour or more of moderate or vigorous aerobic physical activity a day, including vigorous-intensity physical activity at least three days a week, according to the U.S. Department of Health and Human Services' Physical Activity Guidelines for Americans.

More information

The Nemours Foundation has more about kids and exercise.