Obesity May Cause Long-Term Molecular Changes in the Immune System: Study

Losing weight may change the scale-but not the body's memory of obesity. A decade-long study published in EMBO Reports reveals that the immune system can retain a lasting “imprint” of obesity, potentially keeping disease risks elevated years after weight loss.

Led by University of Birmingham researchers, the study found that helper T cells—key players in immune defense—carry molecular “tags” formed during obesity. These tags arise through DNA methylation, an epigenetic process that alters how genes behave without changing the genetic code itself. Remarkably, this immune memory can persist for 5–10 years, even after a person achieves a healthy weight.

This lingering imprint may disrupt essential immune functions, including autophagy—the body’s way of clearing cellular waste—and immune aging. As a result, individuals who lose weight may still face a higher risk of conditions such as type 2 diabetes, cancer, and chronic inflammation long after their weight normalizes.

To build a comprehensive picture, researchers analyzed immune cells from diverse groups, including individuals undergoing weight-loss treatments, patients with Alström syndrome, and participants in exercise programs.

The findings challenge the assumption that weight loss alone immediately resets health risks. Instead, they suggest that long-term weight maintenance is crucial, as the immune system’s “memory” gradually fades over time. Encouragingly, scientists believe this process may be accelerated through targeted therapies.

Ultimately, the research reframes obesity as more than a temporary condition—it leaves a biological footprint that lingers beneath the surface.

REFERENCE: Niven, J., et al. (2026) DNA methylation-mediated memory of obesity in CD4 T lymphocytes perpetuates immune dysregulation. EMBO Reports. DOI: 10.1038/s44319-026-00765-w. https://link.springer.com/article/10.1038/s44319-026-00765-w