Underweight children cost NHS as much per child as children with obesity, study finds

The NHS incurs an estimated £340 million in additional health care costs annually due to weight-related health problems in children—but it is not just obesity driving the costs. New research from the University of Oxford reveals that underweight children need comparable medical support as those who are severely obese, challenging assumptions about childhood health priorities.

The study, published in JAMA Network Open, provides the first national picture of health care costs linked to children’s weight, using NHS electronic health records from more than 268,000 children aged 2–15 across England. It found that childhood weight issues—affecting around 2.5 million children—cost the NHS an estimated £340 million each year.

Importantly, the research shows that health care costs rise sharply after a child’s weight is formally recorded, suggesting that identifying weight issues triggers additional medical support—but only if appropriate services are in place.

Key findings that matter for practice

The research tracked health care use in the year before and after children had their weight measured in GP practices, revealing the additional costs (“excess costs”) compared to healthy-weight children:

• Four to five-year-olds with severe obesity had the highest excess costs at £472 per year
• Girls with severe obesity cost more than boys (£253 vs. £138 annually)
• Only white children showed clearly higher health care costs across all unhealthy weight groups.
• Health care use was substantially higher after weight was measured for underweight children, and moderately higher for children with severe obesity.

“This work suggests we may have been looking at this the wrong way,” said Dr. Olu Onyimadu, lead author from Oxford’s Nuffield Department of Primary Care Health Sciences. “It’s not just obesity that drives costs. Underweight children may need comparable support and generate similar costs per capita to the NHS. We need to think about the full spectrum of unhealthy weight when planning services.”

The findings come at a critical time as the government implements its 10-year health plan, which emphasises a shift from treatment to prevention. The research offers NHS decision-makers clear evidence about where to target resources.

Professor Stavros Petrou, co-senior author and NIHR Senior Investigator, said, “These numbers give commissioners and practices the evidence they need to make the case for weight-management services. Early intervention across the weight spectrum could generate substantial savings while improving children’s health.”

The ethnic variations revealed in the study could help the NHS target support more effectively. White children consistently showed higher excess costs when overweight or obese compared with children from other ethnic backgrounds—insights that could help address health inequalities.

Professor Mara Violato, co-senior author based in Oxford Population Health, added, “With 27% of children aged 2–15 living with overweight or obesity, plus those affected by underweight, we are looking at a huge opportunity for preventive care. These detailed cost breakdowns by age and sex can help clinical and budgetary service planners identify which children to prioritise.”

What this means for families and the NHS

The research suggests that once a child’s weight issue is identified, the NHS responds with additional support—but this only works if appropriate services exist. The findings strengthen the economic case for investing in both prevention programmes and weight-management services in primary care.

For parents, the findings indicate that concerns about children being too thin are just as valid as worries about excess weight. The research shows that once weight issues are identified by GPs, children typically receive more medical support—from nutritional advice to mental-health services—highlighting the importance of regular check-ups.

For commissioners and practices developing business cases for new services, the study provides the robust evidence needed to demonstrate value for money. Because the methodology aligns with UK clinical standards, the findings are directly applicable to NHS decision-making.

The research team emphasised that these cost estimates can now be used to assess whether specific weight-management programmes offer value for money, helping the NHS make informed decisions about which interventions to fund. The researchers note that BMI measurements are not routinely recorded for all children in primary care, and future research will explore patterns over longer time periods.

Related content

UK | April 2026 | FA-11628072