Recent research shows that body fat is more than a calorie store; it actively regulates immune responses and blood pressure. Scientists have identified specialized fat depots near the intestines that coordinate immunity against gut microbes, while another study links beige fat around blood vessels to vascular health. These findings challenge simplistic views of fat as merely harmful.
Body fat, long viewed as a passive energy reserve, emerges as a dynamic organ influencing multiple health aspects, according to two new studies. White fat stores energy and secretes metabolism-affecting hormones, brown fat produces heat, and beige fat can switch to heat generation. Subcutaneous fat under the skin poses fewer risks than visceral fat around abdominal organs, which correlates with inflammation, type 2 diabetes, and cardiovascular issues.
In the first study, researchers at Karolinska University Hospital in Stockholm, led by Jutta Jalkanen, examined visceral fat architecture. They discovered that epiploic fat enveloping the large intestine contains abundant immune cells and fat cells that release inflammatory proteins. Gut-derived microbial products activate these cells, prompting nearby immune responses. "Our work shows that fat depots appear to be specialised according to their anatomical location, and those that sit right next to the intestine seem particularly adapted for immune interaction," Jalkanen stated. She added that this fat likely protects against environmental exposures in the gut for people of all weights, though obesity might trigger chronic overactivation, fostering inflammation tied to metabolic disorders.
The second investigation, conducted by Mascha Koenen at The Rockefeller University in New York, explored perivascular adipose tissue rich in beige fat surrounding blood vessels. Experiments on mice lacking beige fat revealed stiffer vessels that overreacted to constricting hormones, raising blood pressure. The effect stemmed from an enzyme, QSOX1, secreted by impaired fat cells; inhibiting it restored normal pressure irrespective of weight. "What this nicely shows is that the communication between different organ systems is critical to understand complex diseases such as hypertension and blood pressure regulation," Koenen explained. Kristy Townsend from The Ohio State University noted that such fat deposits, though smaller in humans, remain relevant and underscore the need to assess adipose effects beyond overall body mass index.
These insights suggest therapies targeting specific fat functions, like enhancing beige fat or immune-fat interactions, rather than just fat reduction. Paul Cohen, also at The Rockefeller University and involved in the second study, reflected on the field's evolution: from seeing fat as a mere storage bag in the 1990s to recognizing it as a multifaceted tissue with diverse cellular roles beyond nutrient handling. The studies appeared in Cell Metabolism (DOI: 10.1016/j.cmet.2025.12.008) and Science (DOI: 10.1126/science.ady8644).
