GENEVA, Switzerland (AFP) — A quarter of teens globally engage in basically no physical activity — not even an hour of exercise a week — the World Health Organization (WHO) said Wednesday, warning that this significantly raises health risks.

The WHO’s new global estimates found that when asked, one in four adolescents aged 11 to 17 report no active days — defined as at least 60 minutes of moderate to vigorous physical activity — in the previous week.

The study, published in The Lancet Global Health, draws on hundreds of population-based surveys from 140 countries and territories, involving more than 3.2 million teens, WHO said.

When extrapolated, the findings amount to some 240 million young people with no active days in the span of a week, the United Nations health agency said.

Overall, adolescents partaking in the studies on average reported being active for 2.7 days a week, while only 14 per cent reported being active on all seven days, the estimates showed.

The WHO warned that “physical inactivity is a major risk factor for heart disease, type two diabetes and some cancers”.

“Helping young people develop active habits early in life is critical to protecting their health and reducing the global burden of these diseases,” it said in a statement.

The organisation lamented the lack of progress, with physical activity among adolescents remaining “virtually unchanged” in the past 15 years, urging societies to step up.

“For 15 years, the world has made almost no progress in getting young people moving, and girls are being left furthest behind,” WHO chief Tedros Adhanom Ghebreyesus said in the statement.

The WHO highlighted a stubborn gender gap when it came to physical activity among teens, with girls far less active than boys in almost every country and region.

According to the estimate, 28 per cent of girls reported no active days, compared to 22 per cent of boys, while only 11 per cent of girls reported being active every day, compared to 17 per cent of boys.

There were also stark differences between nations.

While fully 40 per cent of adolescents in countries like Namibia, Nepal and the Philippines reported no active days, more than 30 per cent of youths in Bangladesh and Serbia reported  daily physical activity, the report showed.

“The answer is not to tell adolescents to try harder. It is to build schools, streets and communities where moving, playing and being active is safe, easy and normal,” Tedros insisted.

The WHO stressed that physical activity was influenced by the environment in which young people live, pointing to things like modes of transportation, access to safe space and the ability to walk or cycle safely.

The school environment, social norms and lifestyles increasingly centred around screens can also have a big impact on activity levels.

“Countries need policies that make physical activity an easy, safe and accessible part of everyday life,” WHO said.