July 31, 2009

Researchers to Kids: “˜Go Out and Play!’

Being active at age 5 helps kids stay lean as they age, even if they don't remain as active later in childhood, a new University of Iowa study shows.

"We call this effect 'banking' because the kids benefit later on. The protective effect is independent of what happens in between," lead author Kathleen Janz, professor of health and sport studies in the UI College of Liberal Arts and Sciences was quoted as saying. "The implication is that even 5-year-olds should be encouraged to be as active as possible because it pays off as they grow older."

The UI team tested the body fat and activity level of 333 kids at ages 5, 8 and 11 using a special scanner that accurately measures bone, fat and muscle tissue. The kids wore accelerometers for up to five days to record their activity level, providing data that is much more reliable than relying on kids or parents to track minutes of exercise.

The study indicated kids who are active at age 5 end up with less fat at ages 8 and 11, even when controlling for their accumulated level of activity. The average 5-year-old in the study got 30 minutes of moderate to vigorous exercise per day. For every 10 minutes over and above that, kids had one-third of a pound less fat tissue at ages 8 and 11.

Janz said further investigation is needed to learn what happens to the active kids' bodies that keeps them in better shape down the road. It is possible that the active 5-year-olds didn't develop as many fat cells, improved their insulin response, or that something happened metabolically that provided some protection even as they became less active.

The study also indicated that boys are more likely to experience the sustained benefit from being active as preschoolers, possibly because they are more active at age 5 than girls, highlighting a need to encourage young girls to exercise. "The CDC recommends that kids get at least 60 minutes of age-appropriate physical activity every day," said Janz, "and an activity like coloring madly won't cut it."

The challenge is it can be difficult to measure minutes of activity, since kids exert themselves in short bursts rather than in continuous activity, like jogging.

So what can parents do? "Avoid long periods -- more than 60 minutes -- of sedentary activity, insist that schools provide morning and afternoon recesses and whenever possible get kids outside. Kids who meet the CDC activity recommendations tend to be kids who spend a fair amount of time outdoors enjoying unstructured play," Janz said. "In the end, it doesn't take that much extra physical activity to see a measurable outcome. Even ten extra minutes a day makes a difference in protecting against excessive fat gains."

SOURCE: American Journal of Preventive Medicine, July 2009