Elsevier

The Lancet

Volume 398, Issue 10298, 31 July–6 August 2021, Pages 429-442
The Lancet

Series
Physical activity behaviours in adolescence: current evidence and opportunities for intervention

https://doi.org/10.1016/S0140-6736(21)01259-9Get rights and content

Summary

Young people aged 10–24 years constitute 24% of the world's population; investing in their health could yield a triple benefit—eg, today, into adulthood, and for the next generation. However, in physical activity research, this life stage is poorly understood, with the evidence dominated by research in younger adolescents (aged 10–14 years), school settings, and high-income countries. Globally, 80% of adolescents are insufficiently active, and many adolescents engage in 2 h or more daily recreational screen time. In this Series paper, we present the most up-to-date global evidence on adolescent physical activity and discuss directions for identifying potential solutions to enhance physical activity in the adolescent population. Adolescent physical inactivity probably contributes to key global health problems, including cardiometabolic and mental health disorders, but the evidence is methodologically weak. Evidence-based solutions focus on three key components of the adolescent physical activity system: supportive schools, the social and digital environment, and multipurpose urban environments. Despite an increasing volume of research focused on adolescents, there are still important knowledge gaps, and efforts to improve adolescent physical activity surveillance, research, intervention implementation, and policy development are urgently needed.

Introduction

Young people aged 10–24 years constitute 24% of the world's population.1 This population includes, as per the Lancet Commission on adolescent health and wellbeing,2 younger adolescents (10–14 years), older adolescents (15–19 years), and young adults (20–24 years), and will be referred to as such throughout this Series paper.3 Both the Lancet Commission2 and the WHO Global Accelerated Action for the Health of Adolescents4 concluded that investing in adolescent health and wellbeing will yield a triple benefit—ie, today, into adulthood, and for the next generation.2 Although adolescence is generally considered a healthy period in a person's life, many non-communicable diseases (NCDs) that manifest later in life are, partly, the result of modifiable risk behaviours established during this time, such as smoking, unhealthy dietary patterns, and low levels of physical activity.5, 6 During the past three decades, there have been major global trends in adolescent health.7 Although a decrease in adolescent disease burden has been observed in many countries during the past 25 years, almost one in five (324 million; 18%) adolescents globally are now overweight or have obesity,7 and there is an increasing burden of adolescent mental health disorders (including depression and anxiety).8, 9 It is estimated that 962·8 million adolescents (53% globally) now live in multi-burden countries, where they face a so-called triple burden of health problems, including infectious diseases, injury and violence, and NCDs.7 Global agendas, therefore, encourage increased efforts to develop a better understanding of, and potential solutions for, health and wellbeing during adolescence.2, 4, 10, 11 To support these efforts, The Lancet launched the 2020 Campaign on child and adolescent health.12

Physical inactivity is associated with many NCDs and substantial economic costs on a global scale.13, 14 Physical inactivity has been estimated to account for 5·3 million deaths per year,13 and is estimated to cost at least US$54 billion in direct health-care costs, of which $31 billion is paid by the public sector.14 Although physical inactivity is recognised as a global pandemic,15 much of the evidence has come from studies of adults,13, 16, 17 in whom its effects on NCDs become apparent.18 However, evidence suggests that the prevalences of NCDs (eg, type 2 diabetes19) and NCD risk factors (eg, hypertension20 and obesity21) in adolescence are increasing. Acknowledging the health risks of long-term neglect of adolescent health and wellbeing, the Lancet Commission on adolescent health and wellbeing2 proposed 12 headline indicators to track progress in adolescent health. However, despite the known health risks of physical inactivity across the life course,13, 17, 22 and the alarmingly low levels of physical activity in the global population,23 no indicator related to physical activity was included. Therefore, physical activity appears to have low priority in adolescent health. It is crucial and timely to refocus the global prevention agenda in adolescence to include physical activity.

It is important that a better understanding of adolescent physical activity is developed, such that effective strategies can be implemented. The implementation of policies and interventions to promote physical activity has the potential to contribute to achieving many of the UN Sustainable Development Goals (SDGs) for 2030.24 WHO's Global Action Plan on Physical Activity 2018–203025 shows how the promotion of physical activity can help reach multiple SDGs. Beyond its direct contribution to SDG 3 (good health and wellbeing),25 co-benefits of promoting physical activity in adolescents include contributions to SDG 5 (gender equality) and, based on the increasing evidence linking physical activity to academic achievement26, 27 and the crucial role of physical education in high-quality education, SDG 4 (quality education). This Series paper provides an overview of up-to-date evidence on adolescent physical activity behaviours, including prevalence, determinants, and consequences, and provides recommendations for action in research and practice. The term physical activity behaviours is used to capture both physical activity and sedentary behaviour; we will indicate when evidence is specific to a type of behaviour.

Key messages

  • The amount of physical activity is low and screen use is ubiquitous among adolescents across the globe; within-country socioeconomic differences vary by country context—adolescents from high socioeconomic backgrounds have better activity profiles than those from low socioeconomic backgrounds in high-income countries (HICs), with the reverse true for low-income and middle-income countries (LMICs)

  • Adolescent physical inactivity probably contributes to key global health problems, including cardiometabolic and mental health disorders, but the evidence is weak; obesity and mental health problems might become auxiliary drivers of physical inactivity, increasing the risk of morbidity and mortality

  • Supportive social and built environments are key drivers of adolescent activity behaviour, and successful policy action should aim for directing change in these areas; adolescents benefit from built environments that promote a range of activity behaviours (including active travel, play, and sport), and a supportive social environment in and out of school; access to supportive built environments is unequally distributed, particularly in LMICs

  • Schools offer an effective avenue to increase physical activity among adolescents, but school-based initiatives have had little success overall and research involving older adolescents (15–19 years) is scarce; there is a need for sustained implementation of multicomponent programmes, co-designed with adolescents, and such interventions require context-specific support for schools to ensure effective implementation and sustainability

  • Many young people across the globe, particularly those aged 15–24 years, are not in educational settings and alternative strategies to reach this population are required; with widespread access to the internet and some evidence of effectiveness, the potential contribution of eHealth and mHealth approaches contextualised to adolescents' needs and life circumstances should be explored

  • The reasons to instigate change are different for decision makers in health, policy, education, and among adolescents themselves; understanding the benefits associated with physical activity, and tailoring messaging around the outcomes most salient to the specific audience will help drive change at multiple levels of a complex system

  • Observational and interventional evidence on adolescent physical activity behaviours comes largely from HICs and younger adolescents (10–14 years); increased knowledge from LMICs, individuals not in school, and older adolescents going through major life transitions (eg, starting employment and parenthood) is urgently required to curb rapid rises in the health consequences of physical inactivity

Section snippets

Adolescence and young adulthood: a period of transition

Adolescence is a key period of human development as psychological and biological changes occur rapidly during this phase of life.4, 6 Adolescence and young adulthood represent substantial transitions in responsibilities and lifestyles in many cultures, as young people shift from school settings to various different pathways, including higher education, family, military, workforce, or unemployment. It is important to be mindful of the global variation in the timings of these pathways. For

Physical inactivity

WHO recommends that children and adolescents younger than 18 years accumulate at least an average of 60 min per day of moderate-to-vigorous intensity physical activity, whereas people who are 18 years or older should accumulate at least 150–300 mins of moderate intensity physical activity or 75–150 mins of vigorous intensity physical activity per week, or an equivalent combination.40 Similar guidelines have been adopted by many countries across WHO regions. The discrepancy of recommended

Health consequences of adolescent physical activity behaviours

These high amounts of adolescent inactivity and sedentary behaviour come with short-term and long-term consequences for health and wellbeing. There is large variation in the consequences considered important to different stakeholders. Although evidence on reducing morbidity and health-care cost might appeal to health professionals and policy makers, academic achievement and mental health might be a priority for educators and parents, whereas wellbeing, social integration, and having fun are

Inactive adolescents: correlates, determinants, and potential solutions

For decades, research has been dedicated to understanding why some people are more active than others.75 Such inquiry regarding the correlates and determinants of physical activity behaviours aims to identify subpopulations at risk of physical inactivity and understand its modifiable causes to inform intervention efforts. Meanwhile, interventions have been tested around the world to identify potential solutions to physical inactivity with variable success.68 Physical inactivity has been

Conclusions

Adolescence is a life stage that is a crucial for the development of healthy behaviours, but adolescent physical activity behaviours and their association with medium-term and long-term outcomes are poorly understood. Adolescents are not sufficiently active and this inactivity is unequally distributed globally and within societies. A whole systems approach with radical change at social, environmental, and systems levels, through multidisciplinary and cross-sectorial collaboration, is required

Search strategy and selection criteria

We identified data for this Series paper by searching Ovid MEDLINE, Embase, PsycINFO, Web of Science, and Scopus using search terms related to adolescents and physical activity for all reviews. For the reviews on health outcomes, additional terms for prospective study design and cardiometabolic or mental health outcomes were included (see appendix pp 13–34 and appendix pp 35–50 for full details). We only included articles published from database inception to Dec 5, 2019, (cardiometabolic

Declaration of interests

The work of EMFvS is funded by the UK Medical Research Council (MC_UU_12015/7) and undertaken under the auspices of the Centre for Diet and Activity Research, a UK Clinical Research Collaboration Public Health Research Centre of Excellence, which is funded by the British Heart Foundation, Cancer Research UK, UK Economic and Social Research Council, UK Medical Research Council, UK National Institute for Health Research, and the Wellcome Trust (MR/K023187/1). UE is supported by the Research

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