Improving support for adolescents living with excess weight

Every year in England, childhood overweight and obesity add an estimated £270 million to the NHS bill – and until now, nobody had put a reliable figure on it. Policymakers knew the problem was large: excess weight affects a growing proportion of children, with lifelong consequences for health and quality of life. But the economic evidence to guide decisions about where to invest, which interventions to fund, and when to act was patchy at best.

Previous estimates relied on small samples, short follow-up, or assumptions borrowed from adult data. The gap between the scale of the challenge and the evidence base left commissioners and planners working partly in the dark.

Our approach and partners

Researchers at the University of Oxford's Nuffield Department of Primary Care Health Sciences and Nuffield Department of Population Health, working with the University of Sydney and supported by NIHR ARC Oxford and Thames Valley, set out to fill that gap.

They analysed linked national electronic health records from the Clinical Practice Research Datalink and Hospital Episode Statistics – covering more than 268,000 children – to produce the first England-specific estimates of NHS costs by weight status. They then used longitudinal data from the UK Millennium Cohort Study to track how children move between weight categories as they grow.

Complementary systematic reviews drew together evidence from over 150 economic evaluations of childhood weight interventions worldwide, identifying what works, what offers value for money, and where critical evidence gaps remain.

What we found – and why it matters

1. Childhood excess weight costs the NHS approximately £270 million a year. Children with severe obesity incurred the highest excess costs – around £190 more per child per year than children of healthy weight – with significant variation by age, sex, and ethnicity. These are the first national cost estimates derived from routinely collected healthcare data in England.
2. Children's weight trajectories are not fixed – but the window for change narrows with age. Younger children were more likely both to develop and to resolve excess weight. As children grew older, moving back to a healthy weight became progressively less likely. This finding challenges assumptions widely used in economic models and strengthens the case for earlier, targeted prevention.
3. Existing economic evaluations have significant gaps. The systematic review of over 150 studies identified which intervention types are most likely to be cost-effective, but also exposed consistent weaknesses – particularly around long-term effect persistence and reporting by subgroup – that limit the confidence policymakers can place in current evidence.

Findings were published in JAMA Network Open and PharmacoEconomics, and reached wider audiences through national media coverage including the BBC.

What this means

This evidence gives commissioners and planners something they previously lacked: robust, England-specific figures to build the economic case for prevention.

By quantifying NHS costs and identifying the critical windows when intervention is most likely to succeed, the work supports more informed decisions about where to direct resources. It also exposes inequalities in healthcare costs across ethnic groups and age bands – information that can help target action where it is most needed.

The ultimate prize is a shift from treating the consequences of excess weight to preventing them, reducing avoidable long-term pressure on NHS services.

What needs to happen next

Economic evidence needs to become a routine part of childhood obesity policy and programme design, not an afterthought. Decision-analytic models should adopt the age-specific transition estimates this work has produced, rather than relying on outdated assumptions.

A key next step is estimating the lifetime NHS costs attributable to childhood obesity – connecting the childhood weight trajectories observed here to long-term health and economic outcomes. Closer collaboration between researchers, Integrated Care Boards, local authorities, and national bodies is needed to translate this evidence into scalable, sustainable prevention strategies.

Lessons for future research

This programme demonstrated the value of combining large-scale routine data with longitudinal cohort analysis to answer questions that neither source could address alone. A critical methodological finding was that childhood weight transitions are not time-homogeneous – younger children move into and out of unhealthy weight more frequently, while resolution becomes less likely later. Incorporating these age-specific rates into economic models changes projected costs and benefits and shifts the case towards earlier intervention.

Practical challenges included harmonising Clinical Practice Research Datalink and Hospital Episode Statistics datasets and handling missing or implausible measurements. The systematic review exposed consistent methodological weaknesses across the field – particularly around long-term effect persistence and subgroup reporting – that future evaluations should address to improve comparability and policy confidence.