Type 2 diabetes used to be a condition linked to ageing and getting older. It’s the most common metabolic chronic condition in elderly people in the UK, and the likelihood of developing diabetes increases dramatically after the age of 45. People of south Asian heritage have a higher prevalence of type 2 diabetes, and I’ve grown up watching my grandparents and elderly relatives develop it, one after another. India is often referred to as the “diabetes capital of the world”, accounting for 17% of the total number of diabetes patients worldwide. But in Britain, recent data has shown a major change in the profile of who is getting diabetes: it’s now young people. The number of under-40s being diagnosed with type 2 diabetes has risen 39% in the past six years. This was especially the case for people from deprived areas and those from black and south Asian backgrounds. In 2022, Diabetes UK highlighted that the number of children receiving treatment for type 2 diabetes in England and Wales had increased by over 50% over the previous five years. The reason for these increases is not a mystery to experts. They are tightly linked to being overweight, and especially to carrying adipose (fat) tissue around internal organs and the waist. As one diabetes specialist at the Royal Infirmary in Edinburgh told me, “It’s very rare to see someone with normal BMI [body mass index – a crude metric of someone’s weight classification] diagnosed with type 2 diabetes in their 30s, except for south Asians where genetic predisposition is so strong”. She continued that type 2 diabetes in younger people is strongly linked to being overweight and obese (81% of children with type 2 diabetes are living with obesity), but occasionally there is an unexplained anomaly or genetic basis. Examining the links between BMI and diabetes, a study of more than a million people found that diabetes is more likely at a BMI of 30 or over if you’re from a white background, 28 if you’re black, 24 if you’re south Asian and 21 if you have Bangladeshi heritage. What exactly is diabetes? It’s a condition in which the body develops resistance to insulin, a hormone that turns food into energy. With diabetes, fat, liver and muscle cells do not respond to insulin, and so glucose doesn’t get into these cells to be stored for energy. As the glucose has nowhere to go and remains circulating, the resulting high blood sugar levels cause issues such as fatigue, numbness in the feet, joint pain, increased thirst, more frequent urination, blurred vision and diminished immune response. Untreated diabetes damages the blood vessels and kidneys and can lead to heart attacks, strokes and even blindness. The cellular mechanism underlying the link between obesity and diabetes is complex, but to put it simply, adipose tissue releases substances (such as fatty acids, hormones and cytokines) that play a role in the development of insulin resistance. As with many health issues, the real solutions to the increasing rates of diabetes in young people are more political than medical. Reducing rates of overweight and obesity, especially in children, is an ongoing challenge for most high-income countries, and an emerging challenge in low- and middle-income ones. While awareness of symptoms is important, as well as early screening to identify pre-diabetes, we know in public health that education has its limits. Just telling people the risks of being overweight hasn’t made any impact at a population level, according to studies by the World Cancer Research Fund. The key issue here is inequality; a true solution would include making healthier food and physical activity more accessible, affordable and available. The cost of living is rising in Britain, and that means the price of fruit and vegetables, and healthy meat and dairy products is going up, while leisure and sports centres are closing. It’s not surprising that rates of overweight and obese people are increasing in almost all age groups in Britain, and that they are highest in the most deprived areas. Again we see the false economies that the UK government makes when it creates policies about health. It should be investing in public health and prevention, including anti-obesity strategies – such as bans on multi-buy deals and TV advertising of junk food before 9pm, and and subsidies for nutritious foods – and healthier environments for individuals, especially those from deprived areas. One clear focus could be school meals, in which ultra-processed foods make up 72.6% and 77.8% of primary and secondary school lunches respectively (between school-provided lunches and packed lunches): the consequence is British children having the highest level of ultra-processed food intake in Europe. Yet the UK government has delayed tackling overweight and obesity, meaning that the NHS has to spend more on acute and chronic care for those developing diabetes and needing treatment and support. Unless this dynamic changes, Britain may be called in the future “the under-40s diabetes capital of the world”. Prof Devi Sridhar is chair of global public health at the University of Edinburgh