Nearly one in three adults in England were living with obesity in 2025 according to the largest study of obesity trends ever undertaken in the country.
Robert Fletcher, a postgraduate student at St John's College, led a University of Cambridge study analysing electronic NHS health records from almost every adult in England, revealing an unexpected acceleration in new obesity cases among younger adults.
He said: “Levels of obesity in England have worsened since the pandemic, with nearly one in three people now affected.
"We're also seeing large disparities across the country. The rise in new cases among young adults is especially concerning.
“Beyond the implications for their own long-term health, obesity is associated with infertility, adverse pregnancy outcomes and child obesity, which may perpetuate intergenerational cycles of health inequality."
Rates of new diagnoses for people in their thirties were nearly 20 per cent higher in 2024-25 than they were in 2019-20, according to the study published in The Lancet Diabetes & Endocrinology. For people in their twenties, new cases jumped by 16 per cent.
These increases were higher than in older age groups – although the most common ages for diagnosis remained the forties and fifties. New cases fell in those aged 60-79, which could be down to the use of weight loss drugs as this age group is one of the most likely to be able to afford them privately.
Experts said the trend towards earlier diagnosis was worrying given obesity increases the risk of illnesses such as diabetes, heart disease and cancer.
Alongside the age-group breakdown, the team also identified significant differences between different ethnic groups – earlier onset of obesity was more common in ethnic minorities – while the areas with the highest levels of deprivation also saw steeper rises.
These patterns, when it comes to obesity, are well established, but the acceleration in new cases among younger adults was more unexpected, the researchers said.
“On our high streets there has been a proliferation of takeaways and fast food outlets and unhealthy food has been heavily advertised as these age groups have been growing up“
Fletcher said while the study did not investigate the causes behind the rise, he felt there were three key factors.
He said adults in their twenties and thirties had grown up during a period when there was a boom in the unhealthy food market.
"They have been surrounded by unhealthy food in their formative years. On our high streets there has been a proliferation of takeaways and fast food outlets and unhealthy food has been heavily advertised as these age groups have been growing up."
He also said the pandemic followed by the cost of living crisis was likely to have had a bigger impact on younger age groups.
Obesity is now more common in the UK than hypertension and almost three times as common as smoking. It is linked to a wide range of serious conditions, including cardiovascular disease, stroke, cancer, type 2 diabetes and kidney disease.
The team – from the University of Cambridge, British Heart Foundation and George Institute for Global Health - analysed 55 million adult NHS patient records to identify who was being diagnosed with obesity. Those who were already recorded as obese were excluded.
Among those aged 30 to 39 there were 24.1 new cases diagnosed per 1,000 people in 2024-25 compared to 20.3 in 2019-20.
Among those aged 20 to 29 there were 20.3 new cases per 1,000, up from 17.5 five years earlier.
Angela Wood, Professor at the University of Cambridge and Associate Director at the British Heart Foundation Data Science Centre, said: "By analysing electronic health records from the entire adult population of England before, during and after the pandemic, we have generated the most comprehensive evidence to date on how obesity risk and burden are increasingly diverging across multiple dimensions of inequality."
The researchers say the findings demonstrate the importance of secure access to whole-population health data to understand emerging public health challenges and provide evidence to tackle widening health inequalities.
