The majority of older children and teens around the world are not getting enough exercise, putting their current and future health at risk, according to new research from the World Health Organization (WHO).

For the study, published in The Lancet Child & Adolescent Health journal, researchers analyzed data collected between 2001 and 2016 from 1.6 million school-going children in 146 countries.

They found that 81 percent of young people aged 11 to 17 are currently not meeting WHO’s physical activity recommendation for that age group — at least an hour of moderate-to-vigorous exercise daily.

They also found a significant physical-activity gender gap. A discouraging proportion — 78 percent — of boys are not currently active enough, but that figure jumps to a dismal 85 percent for girls.

In fact, in only four countries (Afghanistan, Samoa, Tonga and Zambia) are girls as physically active as boys. Almost a third of the countries (29 percent) have a physical-activity gap between boys and girls that is more than 10 percentage points, and three out of four countries (73 percent) saw this gender gap widen between 2001 and 2016.

One of the biggest gaps is in the United States, where 80 percent of girls are not active enough compared to 64 percent of boys — a difference of 16 percentage points.

“Urgent policy action to increase physical activity is needed now, particularly to promote and retain girls’ participation in physical activity,” said Regina Guthold, the study’s lead author, in a released statement. Guthold is a technical officer at WHO’s Chronic Disease Risk Factor Surveillance in Geneva, Switzerland.

Regular physical activity is an essential component of young people’s health. It helps them build strong bones and muscles, improve their heart-lung fitness, control their weight and reduce symptoms of anxiety and depression, according to the Centers for Disease Control and Prevention. It also reduces their risk of developing heart disease, type 2 diabetes, cancer and other medical conditions later in adulthood.

The highest rates of adolescent inactivity were found among high-income Asian countries. Indeed, in South Korea, 97 percent of young people are insufficiently active — the highest level in the world.

The researchers cite two possible factors for why adolescents living high-income Asian countries spend so little time exercising: the emphasis in those countries on education over physical activity and the widespread use of digital and screen-based technologies that encourage children to be sedentary.