July 28, 2009
Listen to a U.S. Department of Health and Human Services report on this study at http://www.hhs.gov/news/healthbeat/2009/09/the_5_year_old_payoff.mp3
Study: being active as a preschooler pays off later in childhood
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, similar to having a savings account at a bank. The protective effect is independent of what happens in between," said lead author Kathleen Janz, professor of health and sport studies in the UI College of Liberal Arts and Sciences. "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 gold-standard technology: a special scanner that accurately measures bone, fat and muscle tissue, and an accelerometer that measures movement every minute. The kids wore accelerometers to record their activity level for up to five days, providing much more reliable data than relying on kids or parents to track minutes of exercise.
The study, published this month in the American Journal of Preventive Medicine, indicates that kids who are active at age 5 end up with less fat at age 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 on top of 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 may be 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 CDC recommends that kids get at least 60 minutes of age-appropriate physical activity every day, and an activity like coloring madly won't cut it," Janz said.
The challenge is that it can be difficult to measure minutes of activity, since kids exert themselves in short bursts -- think sprinting after a ball -- rather than continuous activities, 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 10 extra minutes a day makes a difference in protecting against excessive fat gains."
Co-authors of the paper, "Sustained Effect of Early Physical Activity on Body Fat Mass in Older Children," included researchers from the UI departments of epidemiology, preventative and community dentistry, and pediatrics.
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