In its first such guidelines for children that young, the health department said kids under five who can walk should be physically active for at least three hours a day. Officials also said parents should reduce the amount of time such kids spend being sedentary while watching television or being strapped in a stroller.
The three hours of activity should be spread throughout the day. Officials said the children's daily dose of exercise is likely to be met simply through playing but could also include activities such as walking to school.
For babies who can't walk yet, the government said physical activity should be encouraged from birth, including infants playing on their stomachs or having swimming sessions with their parents. The government said children's individual physical and mental abilities should be considered when interpreting the advice.
"It's vital that parents introduce children to fun and physically active pastimes to help prevent them becoming obese children, who are likely to become obese adults at risk of heart disease, diabetes and some cancers," Maura Gillespie, head of policy and advocacy at the British Heart Foundation, said in a statement.
Nearly a quarter of British adults are obese, and experts estimate that by 2050 about 90 percent of adults will be heavy.
According to a 2008 health survey that used devices to measure how much people actually exercised, officials found only about five percent of Britons meet the government's minimum physical activity advice -- about 150 minutes of moderate to vigorous exercise every week, including some every day.
For children aged five to 18, Britain recommends at least one hour of exercise, but that should include intensive activities to strengthen muscles and bones.
In the U.S., the Centers for Disease Control and Prevention advises children and teenagers to get about one hour or more of physical activity every day.
According to the Institute of Medicine, an independent organization in Washington, D.C., toddlers should get at least 15 minutes of exercise for every hour they spend in child care.