RODALE NEWS, EMMAUS, PA—A child’s screen time is a legitimate parental concern. But according to a study just published in the American Journal of Clinical Nutrition, it may not be the best target for fighting obesity in childhood. In the study, the time kids spent getting vigorous exercise was more indicative of their weight than the time they spent planted in front of a screen.
THE DETAILS: Researchers at the Medical Research Council Epidemiology Unit in Cambridge, England, used data from the SPEEDY (Sport, Physical Activity and Eating Behavior, Environmental Determinants in Young people) study to investigate factors that contribute to obesity in childhood. They looked at 1,892 9- to 10-year-old British children, all of whom wore devices on their hips for 12 weeks to assess how physically active they were, and whether their activity was light-intensity, moderate-intensity, vigorous-intensity, or moderate-plus-vigorous intensity. The children’s waist circumference, body mass index, and body fat index was also measured, and the children themselves reported the time they spent in front of TV, computer, and video screens.
The researchers found that the children who spent the most time being sedentary weighed the most. But the time children spent being vigorously physical active was actually more indicative of their weight than the time they spent sedentary. “Overall sedentary time is a risk factor [for overweight], whereas total active time is a ‘health’ factor,” explains Ulf Ekelund, PhD, professor and program leader at the Medical Research Council Epidemiology Unit in Cambridge, England, and author of the study. “But according to our study, the association between vigorous-intensity activities and adiposity was stronger than that between sedentary time and adiposity.”
WHAT IT MEANS: This study doesn't show a cause-and-effect relationship between exercise (or lack thereof) and obesity and childhood. But it makes a good case that keeping your kids active may be a more powerful way to keep them at a healthy weight than limiting the time they spend in front of the TV or computer. The study authors conclude: “Interventions to curb the growing obesity epidemic may need to incorporate higher-intensity-based activities.”
What’s higher-intensity? Ekelund explains: “Walking at slow pace is likely categorized as light intensity, whereas power walking as fast as possible without starting jogging is, for most individuals, a vigorous activity. Activities kids frequently perform, such as outdoor play, running, skipping rope, cycling, football, and in-line skating, are usually performed at moderate to vigorous intensity.”
Here’s how to ensure your child’s activities encourage good health:
• Encourage intense play. “The vast majority of health agencies suggest that children should participate in at least moderate intensity activity for at least 60 minutes per day,” says Ekelund. “I agree that a good strategy is to keep kids active by promoting outdoor play, transportation by means of walking and bicycling, and participation in sports and other outdoor activities.” Get them the equipment or gear they need to participate in their favorite activities, and set an example they can follow by being active yourself.
• Don’t forget diet. Activity is only one side of the equation. “To maintain a healthy weight, you also need to consider the other side of the energy balance equation,” reminds Ekelund—“energy intake." Just because your child is vigorously active doesn’t mean he can vigorously devour a bag of Cheetos a day and maintain a healthy weight. “For example, a 10-year-old child can consume a small portion of french fries—about 230 calories—in just a few minutes,” Ekelund explains. “But it takes at least 30 minutes of continuous, vigorous activity like cycling, fast swimming, or jogging to burn this off.”
• Continue to restrict TV time…but not for the reason you might think. “The American Academy of Pediatrics advises limiting children’s TV viewing to 2 hours a day,” says Ekelund. And that’s a good rule of thumb, not because sedentary time directly translates to overweight, but television viewing is frequently associated with unconscious snacking, which increases caloric intake. "In fact, in a previously published study of mine, we found that TV viewing was associated with increased fat mass in children," says Ekelund. "This association was explained by eating while viewing TV, not just being sedentary viewing TV.” Limit the amount of snacks they can have while TV-watching, and give them healthy choices like fruit. And again, curb your own tendency to reach for a bag of chips every time you turn on the television, so it doesn't become the norm for them, too.