A comprehensive global study by the University of South Australia has revealed a troubling convergence of poor lifestyle behaviours among teenagers, significantly heightening their risk of developing preventable chronic diseases such as obesity, cardiovascular disorders, and diabetes.
The study, encompassing over 293,770 adolescents aged 12 to 17 from 73 countries across five WHO regions, assessed clusters of behaviours including physical activity, diet, and screen time.
The results were alarming. It found that a majority of teenagers engage in multiple unhealthy habits. Specifically, 85% did not meet recommended physical activity levels, 80% failed to consume adequate fruits and vegetables, 50% regularly consumed fast food, 39% drank soft drinks excessively, and 32% reported prolonged screen time.
In total, over 92.5% of adolescents reported two or more unhealthy behaviours. The health implications are significant, as each additional unhealthy habit compounds the risk of non-communicable diseases such as obesity, heart disease, and type 2 diabetes.
Breaking down the statistics further, the study revealed that 7% of teenagers had one unhealthy habit, 30% had two, 36.5% had three, 21.5% had four, and 4.5% engaged in all five risky behaviours. Across all WHO regions, less than 1% of adolescents exhibited none of these unhealthy behaviours—a finding that underscores the global nature of this growing crisis, said the study.
Dr. Ming Li, lead researcher at UniSA, said the adolescent years are a pivotal phase for shaping lifelong health outcomes.
“The teenage years are a critical window for growth and development – physically, mentally, and emotionally – and they set the foundation for long-term health,” Dr. Li remarked.
“But with junk food so readily available, and physical activity often replaced by screen time, more teens are picking up multiple unhealthy habits that could lead to serious health issues down the track.”
The study's relevance is underscored by the South Australian government’s new ‘LiveLighter’ campaign, aimed at addressing obesity and lifestyle-related diseases.
The report highlights a geographic disparity. Adolescents in high-income countries, including regions such as the Americas and Eastern Mediterranean, were notably more likely to exhibit multiple unhealthy behaviours. In fact, 13% of teenagers in these areas reported all five risk factors.
Although Australia-specific data was not included, Dr. Li noted that adolescents in the country likely mirror these trends, particularly given Australia’s alignment with other developed nations in lifestyle and dietary access.
“Some of what we see comes down to rapid urbanisation, sedentary school environments, and limited access to safe recreational spaces, particularly in low- and middle-income countries,” he observed.
“On top of this, taste preferences, household income, and limited availability of fresh produce – especially in disadvantaged areas – make healthy choices harder to access and maintain.”
Despite the grim findings, the study did identify key protective elements. Supportive family environments reduced the likelihood of teenagers engaging in four or more unhealthy behaviours by 16%, while a strong peer group led to a 4% reduction. Households that were food-secure reduced this risk by 9%.
Dr. Li has called for comprehensive interventions to combat this worrisome trend.
“It’s clear we need systemic action – better school-based physical activity programs, urban design that gives teens access to green spaces, policies that make healthy food affordable, and limits on junk food marketing to children,” he said.
“Ultimately, good health needs to be an easier, more accessible choice – not one that requires privilege, planning, and willpower.”
As adolescent health trends continue to shift, the findings underscore the urgency of moving beyond individual responsibility to address the broader structural conditions shaping the well-being of future generations. More so because, the rate of obesity—the mother of most non communicable diseases-- among adolescents have significantly increased globally, with a rise from 8% in 1990 to 20% in 2022, according to the World Health Organization (WHO). This trend is observed in both boys and girls, with 21% of boys and 19% of girls in 2022 considered overweight, according to the WHO.
