New study highlights inconsistent impact of combined diet and activity interventions in adolescents
A new systematic review and meta-analysis published in Obesity Reviews explores the global evidence on interventions that combine physical activity and dietary changes to improve adolescent health.
The findings suggest that while some programmes have shown promise in reducing body fat and improving behaviours, overall effects remain inconsistent—and equity considerations are often missing.
Led by researchers from Loughborough University and international partners, the review analysed 36 controlled intervention studies targeting adolescents aged 10–19. Most were conducted in high-income countries and delivered in school settings. Despite efforts to address both physical activity and dietary behaviours simultaneously, only a small number of interventions successfully changed all targeted behaviours.
What the study found
- Behavioural impact was mixed: Only 14% of interventions showed positive changes in all assessed behaviours. Most programmes changed at least one behaviour, but few consistently improved both diet and physical activity.
- Body composition changes were limited: A meta-analysis found a significant reduction in BMI z-scores and body fat percentage, but no significant change in BMI itself—suggesting modest effects on overall adiposity.
- School settings dominated: Nearly 80% of interventions were school-based, raising questions about scalability and sustainability across different contexts.
- Equity data largely absent: Most studies failed to assess outcomes by socioeconomic status, gender, or ethnicity. This limits understanding of how effective—or accessible—interventions are for vulnerable populations.
Implications for policy and practice
The review emphasises the importance of designing interventions that reflect the real-world complexity of adolescent lives. Adolescents are influenced by a range of social and environmental factors—from peers and parents to policies and digital media. Interventions that focus solely on individual education or behaviour change may not be enough.
Key recommendations include:
- Incorporating whole-systems approaches that engage multiple sectors and settings beyond schools.
- Designing programmes that are culturally relevant and adaptable to different socioeconomic environments.
- Reporting and analysing equity data to understand who benefits and where gaps remain.
- Involving adolescents in intervention design, to ensure strategies are practical, engaging, and meaningful.
A call for better evidence
Despite the breadth of studies reviewed, the authors highlight several limitations in the current evidence base—including inconsistent outcome measures, limited reporting on behaviour change techniques, and a lack of robust process evaluations. Importantly, very few interventions were conducted in low- or middle-income countries, leaving major knowledge gaps about what works in diverse global settings.
As adolescent obesity continues to rise globally, there is an urgent need for well-designed, equity-informed interventions that support healthier behaviours early in life. This review provides a foundation for future research and underscores the complexity of addressing obesity through behavioural change alone.
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World Obesity publishes four scientific, peer-reviewed journals, each focusing on a different area of obesity research: systematic reviews, pediatrics, clinical treatment, and science and practice.
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