Fast food, gadgets and zero greens: a direct path to health problems in teenagers

When a cheeseburger costs less than a bowl of strawberries, it's clear that the odds of making a healthy choice are inherently unequal—especially for teenagers.

Now, a new study from the University of South Australia shows that it’s not just teenagers’ unhealthy eating habits that are at play, but a worrying clustering of lifestyle choices that puts most teenagers at serious risk of developing preventable diseases in the future. The findings are published in the journal Nutrients.

The study involved more than 293,770 adolescents aged 12 to 17 years from 73 countries covering five World Health Organization (WHO) regions. The researchers assessed a combination of behaviors such as physical activity, healthy food consumption and screen time, and found the following:

• 85% of teenagers do not get enough physical activity
• 80% don't eat enough fruits and vegetables
• 50% regularly eat fast food
• 39% drink too many sugary soft drinks
• 32% spend too much time in front of screens

Overall, more than 92.5% of teens reported two or more unhealthy behaviors that increase their risk of developing chronic diseases such as obesity, heart disease and diabetes.

In detail:

• 7% of teens reported one unhealthy habit
• 30% - about two
• 36.5% - about three
• 21.5% - about four
• 4.5% - about all five

Across all WHO regions, less than 1% of adolescents had no bad habits at all.

The research is particularly relevant in light of the South Australian Government's new 'LiveLighter' campaign to tackle obesity.

Lead author of the study, Dr Min Lee from the University of South Australia, notes that habits formed in adolescence lay the foundation for behaviour in adulthood:

“Adolescence is a critical window for physical, mental and emotional development, and it forms the foundation for long-term health,” says Dr. Lee.

“But with such easy access to unhealthy foods and physical activity being replaced by screen time, more and more teenagers are adopting a host of unhealthy habits that can lead to serious health problems later in life.”

The study also found clear regional differences:

Adolescents in high-income countries – including the Americas and the Eastern Mediterranean – were more likely to report more harmful behaviors, with 13% of adolescents in these regions having all five risk factors.

Although the data for Australia was not analysed separately, Dr Lee suggests that Australian teenagers are likely to show similar rates to teenagers in other developed countries.

According to Dr. Lee, such trends are influenced by global social changes:

“Some of the phenomena we see are related to rapid urbanisation, sedentary lifestyles in schools and limited access to safe spaces for active recreation, particularly in low- and middle-income countries,” he says.

“Add to this taste preferences, family income levels and limited availability of fresh produce – particularly in disadvantaged areas – all make healthy choices less accessible and harder to maintain.”

While most teens report a variety of unhealthy habits, the study also found several protective factors that may help:

“If adolescents have a supportive family and a supportive peer group, their risk of having four or more unhealthy behaviors is reduced by 16% and 4%, respectively,” says Dr. Lee.
“And if the family is food secure, the risk is reduced by another 9%.”

Dr Lee stresses that the findings highlight the need for comprehensive, multi-level strategies that go beyond individual behaviour and address social and environmental conditions:

“It’s clear we need systemic measures – better school physical activity programmes, city infrastructure that provides teenagers with access to green spaces, policies to reduce the prices of healthy foods and **restrictions on the marketing of unhealthy foods to children,” he says.

“Ultimately, a healthy lifestyle should be an easy and accessible choice, not something that requires privilege, planning and willpower.”