Background: An unbalanced dietary intake of omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFAs) has been associated with chronic inflammation and oxidative stress, both of which contribute to the pathophysiology of obesity. Objective: We aimed to evaluate the effects of a diet with an n-6:n-3 PUFA ratio of 5:1 on body composition, biochemical parameters, and the gene expression of cytokines and antioxidant enzymes in a murine model of diet-induced obesity. Methods: A diet-induced obesity model was established in C57BL6/J mice over 17 weeks. Mice were then fed different diets for 8 weeks: a control diet (chow), a high-fat diet with a 30:1 n-6:n-3 ratio (HFD-30:1), and a high-fat diet enriched with n-3 fatty acids, with a 5:1 n-6:n-3 ratio (HFD-5:1). Body weight and food intake were monitored throughout this study. Biochemical parameters were measured, and the expression of antioxidant enzymes and cytokine genes was analyzed by qPCR. Data were analyzed using GraphPad Prism software. Results: The HFD-5:1 group exhibited a significant reduction in body weight (p = 0.0182), liver tissue weight (p = 0.01), serum glucose levels (p = 0.010), area under the curve (AUC) (p = 0.0161), cholesterol (p < 0.0001), and triglycerides (p = 0.0069) compared to the HFD-30:1 group. The body weight in the HFD-5:1 group decreased to levels comparable to the control group. Additionally, the expression of the inflammatory cytokine genes Ccl2 (p = 0.0389) and Tgfb1 (p = 0.0226) was significantly reduced. Conclusions: These findings suggest that adjusting the dietary n-6:n-3 ratio to 5:1 modulates inflammation-related gene expression and improves metabolic markers in obese mice, supporting its potential relevance for future translational research.

Background: Neck circumference (NC) is a simple anthropometric index of upper-body subcutaneous adiposity. Its relationship with inflammatory cytokines, particularly the anti-inflammatory cytokine IL-10, remains poorly explored, especially in Latin-American populations. Methods: This cross-sectional study analyzed data from 80 Mexican adults with obesity (40 women and 40 men). NC, waist circumference (WC), and body mass index (BMI) were measured according to standardized ISAK and NHANES protocols. Fasting glucose, insulin, lipid profile, and HbA1c were evaluated. Finally, serum TNF-α, IL-6, IL-18, IL-10, and hs-CRP were quantified from a subsample. Correlation coefficients and sex-stratified multiple linear regression models adjusted for age and BMI were performed. Results: In the overall sample, neck circumference (NC) was positively associated with triglycerides, VLDL-C, insulin, and HbA1c, and inversely associated with HDL-C. Sex-stratified analyses revealed marked differences. In women, NC showed strong and independent associations with triglycerides, VLDL-C, IL-10, and the IL-10/TNF-α ratio, whereas these associations were not observed in men. Similarly, waist circumference was independently associated with IL-10, and BMI was associated with hs-CRP. Conclusions: NC may serve as a useful surrogate marker of upper-body adiposity and is independently associated with triglycerides, VLDL-C, IL-10, and the IL-10/TNF-α ratio exclusively in women with obesity. These exploratory findings highlight sex-specific differences in the adiposity–inflammation axis and underscore the need for larger longitudinal studies and sex-tailored approaches in obesity research.