Sex-Specific Cytokine Responses and Metabolic Adaptation to Weight Loss in Obesity with Insulin Resistance.

Background/

Objectives

Obesity-related insulin resistance is accompanied by chronic low-grade inflammation, but the extent to which weight loss modifies circulating cytokines in a sex-specific manner remains insufficiently understood. The aim of this study was to assess sex-specific cytokine responses and metabolic adaptation in adults with obesity and insulin resistance following a six-month weight-reduction program (WRP).

Methods

Thirty-six participants (24 women and 12 men) with a value of Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) ≥ 2 underwent an individualized low-calorie diet combined with moderate physical activity and health education. Anthropometric, body composition, biochemical, oxidative stress, and cytokine parameters were evaluated before and after the intervention.

Results

Both women and men showed significant reductions in body mass, Body Mass Index (BMI), waist circumference, visceral fat area (VFA), body fat mass (BFM), fasting glucose, HOMA-IR, modified Atherogenic Index of Plasma (new-AIP), malondialdehyde (MDA), and Oxidative Stress Index (OSI). Women additionally showed significant decreases in fat-free mass (FFM), skeletal-muscle mass (SMM), total body water (TBW), glycated hemoglobin A1c (HbA1c), and triacylglycerols, whereas cholesterol in high-density lipoproteins (HDL-C) increased significantly in men. Cytokine changes were selective rather than uniform. Interleukin-1 receptor antagonist (IL-1ra), Interleukin 6 (IL-6), and Tumor Necrosis Factor alpha (TNF-α) decreased in both women and men. In sex-stratified analyses, IL-1β decreased significantly only in women, whereas IL-7 decreased significantly only in men. ClinicalTrials.gov Registration: [NCT07645105] (retrospectively registered on [11 June 2026]).

Conclusions

A 6-month lifestyle-based weight-reduction program in adults with overweight or obesity and insulin resistance was associated with metabolic improvement, reduced oxidative stress, and partial attenuation of obesity-related low-grade inflammation. The observed cytokine and metabolic changes suggest sex-related patterns of immunometabolic adaptation to weight reduction. However, these findings should be interpreted cautiously because of the relatively small sex-stratified subgroups and the number of cytokine endpoints analyzed, and they require confirmation in larger, sex-balanced studies.