The study, based on data from 1.6 million people in 146 countries, found that more than 80% of adolescents aged between 11 and 17 did not meet a WHO recommendation for at least an hour of physical activity a day.
“Four in every five adolescents do not experience the enjoyment and social, physical, and mental health benefits of regular physical activity,” said Fiona Bull, a specialist in activity and health and a co-author of the work.
She urged policymakers worldwide to “act now for the health of this and future young generations”.
Globally, girls are more inactive than boys, with 85% of girls and 78% of the boys surveyed failing to hit the daily exercise target.
The study looked at school-going adolescents over 2001-2016 and its authors say there is nothing to suggest the pattern has improved since.
Leanne Riley, a WHO expert on non-communicable diseases and co-author, said sedentary behavior may be due in part to a recent rapid expansion in digital technology that means young people spend more time on phones, tablets and other screens.
“We’ve had this electronic revolution that seems to have changed adolescents’ movement patterns and encourages them to sit more, to be less active, to drive more, walk less, (and) be less active in general,” she told a news briefing.
Country by country, the percentage of teenagers not meeting the goal ranged from 66% in Bangladesh to 94% in South Korea.
In the United States, despite a national plan promoting physical exercise since 2010, obesity rates have risen among adolescents, especially those who eat food high in salt and sugar, studies show.
The WHO study, published in The Lancet Child & Adolescent Health journal, said many sports in the United States seem designed to attract boys more than girls. The inactivity rate among American girls was 81%, compared to 64% for boys.
Riley said that as teenage activity levels stagnate, rates of weight gain and obesity are growing: “These two phenomenon are of concern. We need to do more if we want to halt the rise in obesity ... and promote better rates of physical activity.”
The WHO says being physically active has a range of health benefits, including improved heart, lung and muscle fitness, bone health, and a positive impact on weight.