The risk of developing dangerous obesity-related complications such as type 2 diabetes and cancer may not fully disappear after losing weight, according to a new study. Researchers have discovered that obesity triggers a 'tagging' process on immune cells—which protect the body against bacteria, viruses, and diseases—meaning they remain affected for years after someone sheds excess body fat.
Study Findings from the University of Birmingham
The findings, from the University of Birmingham, reveal that the body can effectively retain a memory of the impact obesity had on it for between five and ten years. This suggests that individuals may continue to face an elevated risk of developing serious complications even after losing weight.
Professor Claudio Mauro, co-lead author of the study from the department of inflammation and ageing at the University of Birmingham, stated: 'The findings suggest that short-term weight loss may not immediately reduce the risk of some disease conditions associated with obesity, including type 2 diabetes and some cancers.'
Methodology and Analysis
To analyze the long-term effects of obesity on the body, researchers took blood samples from four groups of people over a ten-year period. This included obese patients taking weight-loss injections, as well as those with Alstrom syndrome—a rare genetic disorder linked to obesity as it causes reduced physical activity. They also collected blood and fat tissue from participants in a ten-week exercise programme and from individuals with obesity and osteoarthritis undergoing hip or knee replacement surgery.
Furthermore, the researchers studied mice on a high-fat diet and blood donations from healthy human volunteers. Their study found that immune cells—known as helper T cells or CD4+ lymphocytes—carried a memory of obesity through a process called DNA methylation. This causes a 'tagging' effect on DNA in immune cells, which can lead to problems such as reduced waste clearance and a less healthy immune system for up to a decade, potentially resulting in serious complications like metabolic diseases and cancers.
Implications for Weight Management and Treatment
Professor Mauro noted that the findings indicate weight loss may need to be maintained for several years, but emphasized the need for further studies. He also suggested that the results could support the use of SGLT2 drugs—normally used to treat type 2 diabetes, heart failure, and chronic kidney disease by triggering the body to release excess glucose in the urine—because they have 'shown promise' in helping the immune system in those with obesity.
Obesity Statistics and Health Risks
Obesity now affects more than one billion people worldwide and continues to rise across Europe, fueled by unhealthy food environments, urban design that discourages physical activity, and widening social inequality. In the UK, an estimated one in 50 adults are now using fat jabs, with demand surging since the National Institute for Health and Care Excellence (NICE) approved Wegovy for NHS use in 2023. Despite more than 1.6 million Britons now taking weight-loss jabs, nearly two-thirds of adults in the UK are overweight, and more than a quarter are obese, equivalent to around 14 million people.
For adults, a body mass index (BMI) of between 30 and 39.9 is classified as obese by the NHS, while anything over 40 is considered severely obese. Obesity has been linked to numerous serious health complications, including type 2 diabetes, heart disease, breast cancer, bowel cancer, and stroke. More than 18,000 preventable cancer cases in Britain are currently attributed to obesity, making it the second biggest cause of cancer after smoking.
Dr. Belinda Nedjai, senior author of the paper from the Wolfson Institute of Population Health at Queen Mary University London, commented: 'Our findings show that obesity is associated with durable epigenetic modifications that influence immune cell behaviour. This suggests that the immune system retains a molecular record of past metabolic exposures, which may have implications for long-term disease risk and recovery.'
