TUESDAY, Feb. 14 (HealthDay News) -- Even if kids spend the rest of their time sitting around, an hour of any physical activity a day will benefit their heart health, English researchers report.

Their study found that children and teens who got more moderate to vigorous physical exercise daily than their peers had better cholesterol levels, blood pressure and weight, which are important for long-term health.

"Parents, schools and institutions should facilitate and promote physical activity of at least moderate intensity in all children and be less concerned about the total amount of time spent sedentary, at least in relation to these cardiovascular risk factors," said study author Ulf Ekelund, group leader of the Physical Activity Epidemiology Program at the Institute of Metabolic Science in Cambridge, England.

"We demonstrated that higher levels of physical activity of at least moderate intensity -- equal to brisk walking -- are associated with [improving] many cardiovascular disease risk factors, regardless of the amount of time these children spent sedentary," he said.

For example, those children who belonged to the most active group had a smaller waist than those in the least active group, he said.

"In adults, this difference is associated with an about 15 percent increased relative risk of premature death," Ekelund said.

The type of activity is not important as long as the intensity is at least equal to brisk walking, Ekelund said. Possibilities include outdoor play, bicycling, dancing, aerobics, walking and playing team sports.

However, the positive benefits of exercise don't necessarily counteract the harmful effects of a couch-potato lifestyle, he said. "There may be specific sedentary behaviors, such as TV viewing, that impose health risks as TV viewing is linked to other unhealthy behaviors [such as snacking]. Therefore, limiting TV time is still important for children's health and well-being," Ekelund said.

The report was published in the Feb. 15 issue of the Journal of the American Medical Association.

For the study, the researchers pooled information from 14 studies involving more than 20,000 children, aged 4 to 18, obtained from an international children's database. A motion sensor measured total activity and time spent sedentary and in moderate and vigorous intensity activity. The actual activities they engaged in were not recorded.

Overall, three-quarters of the children were of normal weight, 18 percent were overweight and 7 percent were obese. They spent an average of 30 minutes per day in some form of moderate to vigorous exercise and 354 minutes a day -- or nearly six hours -- sedentary.

Boys and girls who exercised more than 35 minutes a day had lower blood pressure, lower cholesterol, lower blood sugar, lower triglycerides and were thinner than children who exercised less than 18 minutes a day, Ekelund's group noted.

Average waist size differed by more than two inches between the most active and least active children and teens. And those with the largest waist size at the study's start were the least active at two years' follow-up.

Samantha Heller, an exercise physiologist and clinical nutrition coordinator of the Center for Cancer Care at Griffin Hospital in Derby, Conn., said that "there is absolutely no reason for our children to be fat, sedentary and at risk for cardiovascular disease."

"Exercise, in whatever form it takes, is fantastic for children and teens -- and adults," she said.

Even children who are not cut out for competitive sports, have the innate need to be physically active, Heller said.

"Parents and caregivers need to limit tech time -- computers, iPads, texting, TV -- and let kids be kids, running around playing," she said.

Grown-ups must get involved too, Heller said. "They can jump rope, play tag and throw the Frisbee with the children. Kids will do better in school, develop social skills, enhance coordination, [and] be happier and healthier for it."

More information

For more on kids and exercise, visit the Nemours Foundation.