Researchers have found that obesity may leave a lasting biological “memory” in the immune system, potentially increasing the risk of obesity-related diseases years after a person loses weight. The findings come from a decade-long study published in EMBO Reports.

The European study was led by Professor Claudio Mauro from the University of Birmingham and supported by the National Institute for Health and Care Research (NIHR) Biomedical Research Centre: Birmingham. The team discovered that helper T cells, also known as CD4+ lymphocytes, can retain long-term changes linked to obesity.

Scientists found that a process called DNA methylation adds molecular markers to the DNA of these immune cells. These changes may remain for 5 to 10 years after successful weight loss. Researchers say this lingering “memory” could disrupt important immune system functions, including waste removal and regulation of immune aging.

The research team believes this may help explain why some people remain vulnerable to obesity-related conditions even after reaching a healthy weight.