Eosinophils Shape Sex-Specific Obesity Response

UC Riverside researchers found female mice carry a protective immune-cell population that male mice lack when fed a high-fat diet.

Updated on Nov. 9, 2026 in Weight Loss

Isometric editorial illustration of two blocky tissue modules in contrasting oxblood and mustard tones, one orderly and one jagged, on a slate base. — Researchers at UC Riverside found female mice carry a protective immune-cell population that male mice lack when fed a high-fat diet. AI Illustration. Upload story photo >

Scientists at the University of California, Riverside reported in PNAS Nexus that immune cells called eosinophils respond differently to obesity in female and male mice. The team used high-resolution single-cell sequencing to identify six distinct eosinophil populations in adipose tissue.

Why it matters

The findings suggest that sex differences in immune responses may influence how obesity affects inflammation and metabolic health. Understanding these differences could inform future research into how immune signaling in fat tissue is regulated.

The study is a single-cell sequencing analysis in mice, identifying six eosinophil populations in adipose tissue with female mice carrying a protective population that males lack on a high-fat diet. Whether these patterns translate to people with obesity, where eosinophils have also been found in fat tissue, remains unknown.

The players

University of California, Riverside

A public research university in Riverside, California, whose scientists led the study on eosinophil immune responses to obesity.

The details

Researchers found that in female mice, the protein RELM alpha, produced by macrophages, helped maintain protective communication between macrophages and eosinophils. Male mice on a high-fat diet tended to develop more pro-inflammatory eosinophil populations with a less protective gene signature.

November 9, 2026: Article reporting the PNAS Nexus study findings was published.

Health Landscape

Prior adipose immunology work has linked eosinophils to metabolic tissue health, and this study adds that female and male mice diverge in their eosinophil populations under a high-fat diet. The sex-specific pattern points to why obesity-related inflammation may not be uniform across sexes.

The research is preclinical and does not yet change treatment options or daily health routines. Further work is needed before any immune-based approach to obesity could be considered for people.

The takeaway

Immune responses to obesity may differ between sexes, which could matter for future research design. Researchers are building adipose organoids to test whether guiding immune-cell communication could support healthier fat tissue.