“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 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."