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

The NHS incurs an estimated £340 million in additional healthcare 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 and funded by the National Institute for Health and Care Research (NIHR), provides the first national picture of healthcare 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 healthcare 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 healthcare 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 healthcare costs across all unhealthy weight groups.
• Healthcare 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.

ENDS

Notes to editors:
Funding:
This research was funded by the National Institute for Health and Care Research (NIHR) Applied Research Collaboration (ARC) Oxford and Thames Valley. Dr Onyimadu and Dr Astbury were additionally supported by the NIHR Oxford Biomedical Research Centre and the NIHR Oxford Health Biomedical Research Centre. Professor  Violato was partially supported by the NIHR Oxford Health Biomedical Research Centre. Professor Petrou was supported by an NIHR Senior Investigator Award.

Contact:

To arrange interviews with any of the authors please contact communications@phc.ox.ac.uk.


About the University of Oxford 
Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the ninth year running, and number 3 in the QS World Rankings 2025. At the heart of this success are the twin-pillars of our ground-breaking research and innovation and our distinctive educational offer.

Oxford is world-famous for research and teaching excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research alongside our personalised approach to teaching sparks imaginative and inventive insights and solutions. 

Oxford University’s Medical Sciences Division is one of the largest biomedical research centres in Europe, with over 2,500 people involved in research and more than 2,800 students. The University is rated the best in the world for medicine and life sciences, and it is home to the UK’s top-ranked medical school. It has one of the largest clinical trial portfolios in the UK and great expertise in taking discoveries from the lab into the clinic. Partnerships with the local NHS Trusts enable patients to benefit from close links between medical research and healthcare delivery. 

Within the division, the Nuffield Department of Primary Care Health Sciences is the largest centre for academic primary care in the UK, and leads world-class research and training to rethink the way healthcare is delivered in general practice and other primary care settings. The department’s main research focus is on the prevention, early diagnosis and management of common illness, bringing together academics from many different backgrounds to work together to produce benefits for the NHS, for populations and for patients. www.phc.ox.ac.uk.

Oxford Population Health (the Nuffield Department of Population Health at the University of Oxford) investigates the causes and prevention of disease. The department has around 1000 staff, students and academic visitors working in a number of world-renowned population health research groups, including the Health Economics Research Centre, and other groups working on clinical trials, cancer epidemiology, public health, ethics and health record linkage. It is also a key partner in the Oxford University Big Data Institute.

About the NIHR

The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research. We do this by:

• Funding high quality, timely research that benefits the NHS, public health and social care;
• Investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services;
• Partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research;
• Attracting, training and supporting the best researchers to tackle complex health and social care challenges;
• Collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system;
• Funding applied global health research and training to meet the needs of the poorest people in low and middle income countries.

NIHR is funded by the Department of Health and Social Care. Its work in low and middle income countries is principally funded through UK international development funding from the UK government.