A third of children in the UK are overweight or obese by the time they reach primary school. Many other countries are facing the same issue, with a tenfold increase in the worldwide prevalence of childhood obesity over the past four decades.
International guidelines recommend that young people aged five to 18 should do at least an hour of moderate to vigorous physical activity every day. But globally, eight out of ten adolescents fail to meet these guidelines. In particular, girls and children from disadvantaged socioeconomic backgrounds are less likely to be physically active.
Governments worldwide are attempting to tackle the growing problem of obesity by increasing the amount of physical activity young people are doing on a daily basis. In the UK, for instance, the government’s Childhood Obesity Strategy focuses on helping pupils in schools to move more.
A typical school-based intervention may introduce activity breaks into daily class lessons or add a new physical education lesson through a specialised teacher. It could also include building new playground equipment or assigning physically active homework. In the UK, funding for such initiatives, specifically to finance physical activity in primary schools, has recently doubled to £320m. This is thanks to additional revenue generated from the Soft Drinks Industry Levy.
But while this all sounds well and good, robust evidence for the effectiveness of existing school-based physical activity programmes is lacking. It is also unclear whether all children – irrespective of socioeconomic status – benefit equally.
Our recent research, which examined 17 international trials, shows that current efforts are not working as intended. When the results of these interventions were combined, there was no effect in increasing the amount of physical activity school children engaged in across the full day.
We conducted a review examining previous research on school interventions that aim to improve physical activity. We looked at trials conducted in Europe, Australasia and North and South America. On average, 20 schools and over 450 children were included in each individual study. Physical activity was measured objectively using automatic electronic monitors to capture actual physical activity across the full day, instead of asking students or parents what they remembered doing, which can be highly inaccurate.
What we found was not promising. Overall, the interventions were ineffective in changing the amount of physical activity school children did across the day – compared to children in control schools. Breaking down the data, we found no evidence of effectiveness among girls or boys, or for children from different socioeconomic backgrounds.
So despite the promise of schools being the ideal environment for influencing young people’s health behaviours, the available evidence suggests current efforts are failing.
Beyond the school gate
But this does not mean there should be an end to school-based interventions. But there does need to be a better understanding of what went wrong with these previous initiatives – along with work to improve them.
One reason for the lack of effectiveness, for example, could be that the programmes may not have been implemented as intended in schools. The programmes often include many components and depend on a range of (already busy) school staff implementing them in a particular way. But to what extent this happens is very often unclear. Similarly, we know little about what the main barriers are to implementing full programmes as intended. It could also be the case that school-based initiatives have a positive impact on children’s physical activity during school hours, but that this is not maintained outside school.
Having said that, it is unlikely that substantial changes to physical activity and obesity will be made by focusing only on schools. More work needs to be done to make sure the wider environments children spend time in are supportive for behaviour change – this includes their homes and local communities.
So given that childhood obesity increases the risk of diseases including type 2 diabetes, heart disease and cancer in adulthood, and that together these diseases are estimated to cause around seven in ten deaths worldwide, this is something that needs to happen sooner rather than later.
Rebecca Love, PhD Candidate in the Centre for Diet and Activity Research, University of Cambridge; Esther van Sluijs, Programme lead – Behavioural Epidemiology, University of Cambridge, and Jean Adams, Senior University Lecturer in Dietary Public Health Research, University of Cambridge