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Adults newly diagnosed with severe mental illness (SMI) gain almost four kilograms more than their peers within 15 years but are no more likely to be referred to structured weight-management programmes, finds new research from the University of Oxford.
The research, published today in The Lancet Psychiatry and supported by the National Institute for Health and Care Research (NIHR) , tracked 113,904 adults (including 23,025 with SMI matched to 90,879 without) across 1,454 GP practices. People with SMI gained 5.6 kilograms compared to 1.6kg in those without by year 15 – a difference of 4kg.
Twelve people with lived experience of SMI co-designed the study and advised on outcome selection, ensuring the research addressed real-world concerns about both physical health outcomes and service access.
"When I was first diagnosed, nobody warned me about the weight gain or offered help to prevent it. My weight ballooned and I gained two stone in the first year alone.”
- Alex, a member of the study's lived experience advisory panel
Most concerning was the rapid weight gain in the crucial first five years after diagnosis, when people with SMI gained 4.9kg compared to 1.6kg in people without SMI – a difference of more than 3kg. This weight gain was most pronounced in younger adults aged 40 and under, and those taking antipsychotic medications.
After accounting for factors including age, sex, race and ethnicity, socioeconomic status, alcohol consumption, smoking status, and BMI, people with SMI and a BMI of 25 kg/m² or higher were 10% more likely than people without SMI to receive weight management advice from GPs (incidence rate ratio 1.10, 95% CI 1.07–1.13). However, they were no more likely to be referred to structured weight management programmes (incidence rate ratio 1.00, 95% CI 0.91–1.10), highlighting a significant gap between problem recognition and service provision.
"Weight gain in people with severe mental illness isn't just a number on a scale. It has real consequences for their heart health and life expectancy," said Dr Charlotte Lee, lead author and research fellow at the University of Oxford's Nuffield Department of Primary Care Health Sciences. "Our findings identify a clear window of opportunity. Embedding weight-management referrals into early psychosis care pathways could reverse years of preventable cardiovascular harm."
Dr Felicity Waite, Clinical Psychologist in Experimental Psychology was involved in the design and interpretation of the study results. She also facilitated the involvement of people with lived-experience in the study. She is looking forward to continuing this research. "One route forward is to draw on our psychological understanding of the difficulties people with psychosis face to develop and adapt routes to support people to prevent weight gain in the early period after a diagnosis of psychosis," she said, and added "I hope we will be able to use psychological understanding of psychosis to inform treatment development and opportunities for prevention".
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The original full post can be read here: https://www.phc.ox.ac.uk/news/severe-mental-illness-weight-gain-study-oxford
Access the full paper at: https://authors.elsevier.com/sd/article/S2215-0366(25)00212-3