Most youth around the world get less than an hour of physical activity a day. Better programs and measurements are needed.
Most young people around the world are not getting enough physical activity, putting their health at risk, and girls are generally less active than boys, according to a major new study.
More than 80% of school-going adolescents globally do not meet current recommendations of at least one hour of physical activity per day – including 85% of girls and 78% of boys — according to the study, published in The Lancet Child & Adolescent Health journal and produced by researchers from the World Health Organization (WHO).
The levels of insufficient physical activity in adolescents are compromising their current and future health and contributing to growing obesity rates globally, the authors said.
“Physical activity levels need to go up pretty much everywhere in the world if we don’t want to end up with an unhealthy next generation,” study author Regina Guthold of the WHO said.
The difference in the proportion of boys and girls meeting the recommendations was greater than 10 percentage points in almost one in three countries in 2016, with the biggest gaps seen in the United States and Ireland. Most countries in the study saw this gender gap widen between 2001-2016.
The first-ever study of global physical activity, conducted by researchers from the WHO, Imperial College London and the University of Western Australia, collected data from 1.6 million 11-to-17-year-old students in 146 countries. The assessment included active play, sports, domestic chores, walking, biking and gym class.
Physical activity has many health benefits. It can boost cardiorespiratory and muscle fitness, strengthen bones and have a positive effect on body weight. There is growing evidence that physical activity has positive effects on brain development and socialization, according to the WHO.
The countries with the most active young people are Bangladesh, Slovakia, Ireland and the United States, according to the study. But only a third of adolescents in Bangladesh, the most active country, reached the target.
School-going youth in South Korea, the Philippines and Cambodia were the most inactive, with only 6% of South Korean young people active for at least one hour a day.
Many girls are confined to stereotypical roles.
Girls were less active than boys in all but four countries — Tonga, Samoa, Afghanistan and Zambia. In almost three quarters of the countries, this gender gap widened between 2001-2016.
Guthold said boys may be more active because “in many countries, there are big national sports, such as cricket, soccer and hockey, which are growing and all male dominated.”
“The trend of girls being less active than boys is concerning,” said 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.”
Rachel Colley, a senior research analyst in the Health Analysis Division of Statistics Canada, said girls’ physical activity decreases with age, especially around 12 years old. She cited “physiological changes in women’s bodies that make girls shy away from being active.”
The authors noted that the study included only self-reported information from school-going adolescents. It may have under-reported female-dominated activities such as dance, gymnastics and yoga.
“Girls in a lot of the world are still confined to stereotypical roles, and so much of their activity might occur through domestic chores,” said Mark Tremblay, director of Healthy Active Living and Obesity Research at the CHEO Research Institute in Ottawa.
“They may be doing housework while carrying their little sister on their back, which would certainly be moderate to vigorous physical activity. But they might not consider this physical activity. For them, it’s just part of their daily routine.”
Biases may skew the data.
That is a major limitation of the study, said Tremblay, and why he published a commentary critiquing the research. He said self-reporting often does not reflect the reality of physical activity. He has instead used more direct measures of assessment, including accelerometers, which measure movement.
Tremblay recently completed a study in Mozambique, where he found that almost all children living in rural areas far exceeded the WHO’s guidelines. “And yet they’re ranked 136 out of 146 countries,“ he said. “It’s just blatantly wrong.”
Data from the developing world is not the only information that might be skewed in a self-reported study. Colley said individuals can overestimate their activity because they want to appear healthier than they are or because they have difficulty recalling total daily activity.
When Colley compared self-reported data on Canadian adolescents to accelerometer data, she found on average that teens were overreporting about 20 minutes of activity a day.
Tremblay said the WHO’s rankings might not be accurate, noting that when he collected direct measures of physical fitness — an indicator of physical activity — the results were remarkably different. “Tanzania is by far the number one for kids’ physical fitness, and the U.S. is near the bottom of the list,” he said. “There’s almost no correlation.”
Data only came from students.
Tremblay’s numbers align more closely with global data on obesity rates. In some countries that were ranked more active in the WHO report, obesity rates are relatively high. These nations include the United States, where child obesity rate is 18.5%, and the United Kingdom, where 20% of 10 year-olds are classified as obese.
“This doesn’t mean the WHO did anything wrong,” Tremblay says. “It’s just an inherent limitation to the data they have.”
One of those limitations, Guthold said, is that the WHO collected data only from school-going youth. “We might have seen a different picture if we had included out-of-school adolescents,” she says. Data on this population is hard to access, but “they might be a lot more physically active because they are engaged in manual labour, for example.”
Still, experts agree that the rates of physical activity globally among adolescents are dangerously low.
The WHO called for more effective national policies and programs to promote physical activity. Recent efforts, such as former U.S. First Lady Michelle Obama’s “Let’s Move” campaign, appear to have increased physical activity mainly among boys. More female-targeted policies and programs could be needed.
A broad-based effort is needed.
Efforts to increase physical activity need to be multi-dimensional and engage the healthcare and education sectors, Guthold said. She pointed to Finland, where schools have implemented five physical activity breaks throughout the day to get youth moving.
“Finland is also integrating physical activity into learning. In history class, they use timelines on a staircase to get students to go up and down the stairs,” Guthold says. “The students are doing physical activity without even realizing it.”
Better measurements of physical activity are needed, Tremblay said, because this is a “global crisis that is related to almost all the mental, emotion, social and physical health issues we’re dealing with in the world.”
Natasha Comeau is a fellow in global journalism at the Dalla Lana School of Public Health at the University of Toronto. She holds a Masters of Global Affairs from the Munk School at the University of Toronto where she focused her studies on development and global health.