"More opportunities to meet the needs and interests of girls are needed to attract and sustain their participation in physical activity through adolescence and into adulthood". Exercise, along with healthy eating, is also viewed by experts as key to controlling a global obesity epidemic.
"We absolutely need to do more or we will be looking at a very bleak health picture for these adolescents", study co-author Leanne Riley told journalists ahead of the launch.
An additional benefit of physical activity is improved mental health, Dr.
The Philippines was the most inactive country among boys, whereas South Korea had the least active girl adolescents, with just 3 per cent indulging in physical activity daily.
"We are not seeing any improvements", Riley said.
The study found that the greatest decreases in boys being insufficiently active were Bangladesh - from 73 per cent to 63 per cent, Singapore (78 per cent to 70 per cent), Thailand (78 per cent to 70 per cent), Benin (79 per cent to 71 per cent), Ireland (71 per cent to 64 per cent), and the United States (71 per cent to 64 per cent).
The report authors also pointed to poor infrastructure and insecurity making it hard for adolescents to walk or bike to school.
They also flagged that as it included information from school-going 11 to 17-year-olds only, due to lack of data for out-of-school adolescents which may skew the results for some developing countries.
And while the situation for boys improved somewhat between 2001 and 2016, with inactivity levels dropping from 80 to 78 percent, girls remained at 85 percent.
Most countries in the study (73 per cent, 107 of 146) saw this gender gap widen between 2001-2016. There has been a small decrease of a few percentage points among boys, but not girls, says the study published in the Lancet Child and Adolescent Health journal.
Among girls in general the changes in activity levels were small over the review period, the World Health Organization study found, ranging from a twohttps://www.un.org/sustainabledevelopment/development-agenda/ per cent increase in Singapore - from 85 per cent to 83 per cent - to a one per cent increase in Afghanistan (87 per cent to 88 per cent).
For girls too, the lowest levels of insufficient activity were seen in Bangladesh and India, and are potentially explained by societal factors, such as increased domestic chores in the home for girls.
The US for instance put in place an ambitious national plan for physical activity in 2010, but the efforts "for some reason only seem to reach boys".
The findings are troubling because physical activity is associated with better heart and respiratory functioning, mental health and cognitive activity, which have implications for student learning. The biggest gaps were in the United States and Ireland, at more than 15 percentage points.