By Amy Norton

NEW YORK (Reuters Health) - Childhood obesity is a growing problem, and new research suggests that physical activity levels among youngsters already begin a decline before they start school.

In a study of 244 New Zealand children, researchers found that the children's daily exercise levels generally declined between the ages of 3 and 5, while their time in front of the TV or in other sedentary activities stayed consistent.

Using both parents' reports and an objective measure of daily activity -- a wearable monitor that records the body's movements -- the researchers found that exercise levels dipped among both boys and girls by the age of 5.

Meanwhile, the children spent an average of 90 minutes per day in front of the TV or computer, with another 90 minutes devoted to other sedentary activities like reading and drawing. Those habits were consistent over time, according to findings published in the journal Medicine & Science in Sports & Exercise.

Few studies have looked at preschoolers' activity levels, so it's difficult to tell whether it's natural for physical activity to wane between the ages of 3 and 5, according to lead researcher Dr. Rachael Taylor, of the University of Otago in New Zealand.

However, the findings are potentially concerning, she told Reuters Health. In recent years, obesity has been rapidly increasing even among preschoolers.

In general, experts recommend that children and teenagers be physically active for at least an hour each day. Taylor recommended that parents help their preschoolers get enough exercise by being physically active along with them -- and by putting limits on TV and computer time.

"Children generally love to be active and busy, especially when young," she said, "so it makes sense to optimize that interest as much as possible."

SOURCE: Medicine & Science in Sports & Exercise, January 2009.

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