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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.

Each 2kg/m2 rise in body mass index (BMI) above the normal-weight threshold in women aged 55-79 leads to a 5% rise in annual hospital admissions and 7% rise in healthcare costs. In England, £662 million of the annual hospital admission costs in 2013 could be attributed to overweight or obesity in women of this age group.

This large study, partly funded by the NIHR, looked at over one million women participating in the NHS breast cancer screening programme. Five-year data on hospital admissions, diagnoses and costs were extrapolated to all women in this age group in England. Among findings, it shows that knee joint replacement surgery and diabetes rank high among obesity-related costs.

Considering this alongside costs of primary care, social services and lost productivity, the economic burden of excess weight becomes even more substantial.

This emphasises the urgent need for public health approaches to promote healthy lifestyle behaviour and prevent obesity.

Why was this study needed?

The 2016 Health Survey for England showed that 27% of women were obese (BMI >30kg/m2) while 30% were overweight (BMI 25-30kg/m2). A similar proportion of men were obese (26%), but a greater number were overweight (40%). Only 58% of women and 66% of men were achieving recommended physical activity levels.

Obesity is associated with many chronic diseases, such as diabetes, and places a high demand on health and social care services. Obesity was recorded as a diagnosis for 525,000 hospital admissions in England in 2015/16 and was the main cause of admission for 9,929. Around two-thirds to three-quarters of these admissions were women.

The NHS in England spent £6.1 billion on overweight- and obesity-related illness in 2014/15. The cost to wider society is estimated at £27 billion per year. These costs are only set to rise unless obesity prevalence is reduced.

This study looked at the healthcare cost of increased BMI using data from a large cohort of older women.

What did this study do?

The Million Women Study recruited women aged 50-64 years taking part in the NHS breast screening programme between 1996 and 2001. At recruitment, they completed health and lifestyle questionnaires and self-reported height and weight. A total 1,093,866 women without prior cancer diagnosis were analysed in this study.

Women were linked by their NHS number to the Office for National Statistics and Hospital Episode Statistics. They looked at hospital admissions and day-case procedures, by diagnosis, between 2006 and 2011. Costs of these episodes were calculated using 2012 NHS reference data. This was analysed against BMI category, taking account of age, smoking, alcohol and various socioeconomic factors.

The study doesn’t look at medical care or prescription costs outside of hospital. Self-reported BMI is a limitation, but this has been shown to closely reflect direct measurement.

What did it find?

  • There were 1.84 million hospital admissions during the five year study period.
  • Admission rates were lowest for women in the lower half of the normal weight spectrum (BMI 20-22.5kg/m2) at 321 per 1000 women per year, at an annual cost of £567 per woman. They were highest for severely obese women (BMI >40kg/m2) at 530 per 1,000 women per year and an annual cost of £1,220 per woman.
  • Each 2kg/m2 rise in BMI above 20kg/m2 was associated with a 5.0% rise in admissions (95% confidence interval [CI] 4.7 to 5.2) and 7.4% rise in annual cost (95% CI 7.1 to 7.6).
  • There were 6.6 million women aged 55-79 years in England in 2013. Applying these results suggested that excess weight accounted for £622 million (14.6%) of the total £4.5 billion hospital costs for this population in that year. Over a third of these costs (£258 million) related to musculoskeletal conditions, mostly joint replacement.
  • Further analysis suggested that diabetes may account for 39% of the total costs attributed to overweight and obesity.

What does current guidance say on this issue?

The NICE guideline on Obesity prevention emphasises the need for healthcare professionals, commissioners, employers, local and educational authorities to prioritise obesity prevention. Recommendations include local authorities providing cycling and walking routes, childcare facilities providing active play sessions, and schools and workplaces supporting healthy food choice and physical activity.

The NICE guideline Obesity: identification, assessment and management provides recommendations on obesity management. Multicomponent lifestyle interventions incorporating dietary, physical activity and behavioural components are central to care. Both assessment and management should take account of medical comorbidities.

What are the implications?

Increasing rates of overweight and obesity are a global health concern. This study confirms that hospital admission rates and costs increase proportionally with BMI.

The focus on middle-aged to older women seems acceptable given that most people with obesity admitted to hospital are female. But the study only considers secondary care costs. Add the cost of primary and social care services, and work absence from obesity-related illness and the economic burden becomes even greater.

Prevention of obesity is easier than cure. This is another reminder to focus public health efforts to support healthy lifestyle change. Disease-specific data may help healthcare commissioners identify where to prioritise resources.

Citation and Funding

Kent S, Green J, Reeves G et al. Hospital costs in relation to body-mass index in 1.1 million women in England: a prospective cohort study. Lancet Public Health. 2017;2:e214-22.

This project was funded by Cancer Research UK, the Medical Research Council, and the National Institute for Health Research.



NICE. Obesity prevention. CG43. London: National Institute for Health and Care Excellence; 2006; updated March 2015.

NICE. Obesity: identification, assessment and management. CG189. London: National Institute for Health and Care Excellence; 2014.

NHS Digital. Health Survey for England. London: NHS Digital; 2016.

NHS Digital. Statistics on Obesity, Physical Activity and Diet – England 2017. London: NHS Digital; 2016.

Public Health England. Health matters: obesity and the food environment. London: Public Health England; 2017.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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