Active children

Might population-wide increases in physical activity reduce socio-economic inequalities in the proportion of children who are overweight?

Just half of children in the UK achieve the World Health Organisation’s targets for daily activity, and in England the Government has set its own strategy to tackle this. But would increased physical activity lead to fewer children being overweight or obese? And would it help to address social inequalities in the proportion of children who are overweight? Research from Anna Pearce and colleagues at the UCL Great Ormond Street Institute of Child Health in London suggests more physical activity is unlikely to reduce the prevalence or inequalities in levels of overweight.

Childhood overweight is an important public health problem, with particularly high levels in children living in disadvantaged circumstances. Physical activity is an important determinant of childhood overweight. The World Health Organization (WHO) recommends children should undertake 60 minutes of moderate-to-vigorous physical activity every day. But for many families in England, as in other high-income countries, this is an aspiration rather than the reality.

The UK Government has identified a number of strategies to increase activity among children.  But the potential for physical activity initiatives to help children achieve a healthy weight, if scaled up at the population level, hasn’t previously been assessed. In our research, we focused on the WHO target, and on the likelihood that achieving this will reduce socio-economic differences in levels of overweight or obesity.

We wanted to know how hypothetical government interventions to increase activity might reduce the prevalence and inequalities in childhood overweight at age eleven. Could population-wide interventions, aimed at all, or targeted interventions with high-risk groups, have the greatest effect?

What, specifically, might happen to the prevalence and social distribution of childhood overweight if all children achieved the WHO’s target of 60 minutes’ activity per day? What if we are only able to achieve smaller increases in activity than those required to meet the WHO target?

In our study, 27% children were overweight at age eleven. We found that hypothetical universal interventions to increase physical activity could lead to moderate reductions in this. For example, if 95 per cent of children met the target of 60 minutes of activity per day, the prevalence of overweight (including obesity) would drop to 22 per cent. But more realistic scenarios, in which interventions led to more moderate improvements in physical activity levels (of only a few minutes each day), would achieve only small reductions in overweight within the population.

Children from the most affluent backgrounds were less likely to be overweight  – around one in five children in the top fifth of household incomes were overweight or obese at 11y, compared to one in three among those in the bottom fifth of household incomes. Our analysis suggested these stark social differences in overweight are unlikely to be reduced through meeting the WHO physical activity target. This is partly because children from the highest income group had the lowestlevel of daily activity, with a median of 59 minutes’ moderate to vigorous activity compared 62 minutes for the lowest fifth of the income range.

Even more intensive intervention scenarios, given only to high-risk families (for example those who were overweight or obese at an earlier age, or those living in disadvantaged neighbourhoods), appeared unlikely to address the stark social inequalities experienced by this cohort of children.

Activity targets

The WHO’s physical activity targets are ambitious and, if achieved, are likely to benefit children’s health and wellbeing in a multitude of ways. However our findings suggest that if the Government is serious about supporting children and families – particularly those from poorer backgrounds – to maintain healthy weights, it needs to look elsewhere.

We need, therefore, to know more about how other types of initiatives to reduce childhood overweight might work. Research which aims to inform this debate should look not just at activity levels but also at environmental factors that influence diet, such as taxes on high-sugar foods and foods provided in early-years settings.

What if all children achieved WHO recommendations on physical activity? Estimating the impact on socioeconomic inequalities in childhood overweight in the UK Millennium Cohort Study, by Anna Pearce, Steven Hope, Lucy Griffiths, Mario-Cortina-Borja, Catherine Chittleborough and Catherine Law, is published in the International Journal of Epidemiology, 2019, 134–147.

Anna Pearce is based at the University of Glasgow but carried out this work out in her previous position at the UCL Institute of Child Health.

Steven Hope, Mario Cortina-Borja, and Catherine Law are based at the Population, Policy and Practice Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, UK.

Lucy Griffiths is based at Swansea University but carried out this work out in her previous position at the UCL Institute of Child Health…

 Catherine Chittleborough is at the School of Public Health, Robinson Research Institute, University of Adelaide, Adelaide, SA, Australia.

This blog is based on independent research funded by the National Institute for Health Research (NIHR) Policy Research Programme (Children’s Policy Research Unit). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.