In the battle against obesity, even the very young need to get more exercise, according to two USC health researchers.

Russ Pate and Jennifer O’Neill of USC’s Arnold School of Public Health wrote about the need in a commentary in the most recent Archives of Pediatrics and Adolescent Medicine.

They suggest the federal Physical Activity Guidelines for Americans be adjusted, calling for three hours of daily activity for children 5 and younger. When the guidelines were set in 2008, no recommendations were made for younger children. (Pate was a member of the committee that came up with those recommendations.)

“Because obesity rates have increased in young children, numerous authorities have recommended actions that should be taken to address this problem,” Pate and O’Neill wrote.

Federal health statistics indicate more than one-quarter of children ages 2-5 in the U.S. are obese. While there have been few studies linking that rising statistics to a drop in physical activity in that age group, similar studies have shown the link in older children.

Physical activity for young children should include a combination of light activity — basically just moving around and not sitting in one place — and more energetic activity such as fast walking, dancing, bike riding, swimming or simply active play. Studies indicate most young children get little of the more vigorous exercise.

To reach the three hours a day, children would need to be active about 15 minutes of each hour in the typically 12 hours they are awake.

The U.S. Institute of Medicine in 2011 recommended parents and other caregivers provide light, moderate or vigorous physical activity at least 15 minutes per hour. The commentary suggests the official federal guidelines take a similar approach.