Most teenagers worldwide are not physically active enough, putting their current and future health at risk, a major new study led by the World Health Organization (WHO) has found.

According to the findings, girls are less active than boys, particularly in Ireland.

The results are based on data reported by 1.6 million young people aged between 11 and 17 from 146 countries, who were studied between 2001 and 2016.

They show that 85% of girls and 78% of boys were not meeting current physical activity recommendations, which state that young people should be getting at least 60 minutes of moderate or vigorous exercise per day.

In all but four of the countries studied, girls were less active than boys. In fact, the difference in the proportion of boys and girls meeting activity recommendations was greater than 10 percentage points in almost 30% of countries in 2016, with the biggest gaps seen in Ireland and the US (more than 15 percentage points).

The WHO emphasised that physical activity offers a range of health benefits during adolescence, including improved muscular and cardiovascular fitness, better bone health and a positive impact on weight. It can also have a positive impact on mental health.

Evidence suggests that many of these benefits continue into adulthood.

"Urgent policy action to increase physical activity is needed now, particularly to promote and retain girls' participation in physical activity," commented one of the study's authors, Dr Regina Guthold, of the WHO.

The researchers looked at all types of physical activity, from active domestic chores to active play, PE in school, and sports.

They said that action is needed in a number of sectors of society, including education, road safety and urban planning.

"The study highlights that young people have the right to play and should be provided with the opportunities to realise their right to physical and mental health and wellbeing.

"Strong political will and action can address the fact that four in every five adolescents do not experience the enjoyment and social, physical, and mental health benefits of regular physical activity. Policy makers and stakeholders should be encouraged to act now for the health of this and future young generations," commented the study's co-author, Dr Fiona Bull, of the WHO.

The researchers expressed particular concern about the fact that overall, girls are less active than boys.

According to study co-author, Dr Leanne Riley, of the WHO, "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."

The WHO called on countries to develop or update their policies in relation to physical activity, and allocate the necessary resources to this area.

"Policies should increase all forms of physical activity, including through PE that develops physical literacy, more sports, active play and recreation opportunities, as well as providing safe environments so young people can walk and cycle independently.

"Comprehensive action requires engagement with multiple sectors and stakeholders, including schools, families, sport and recreation providers, urban planners, and city and community leaders," Dr Bull added.

The study was conducted by researchers from the WHO, Imperial College London and the University of Western Australia.