FGF21 and obesity due to melanocortin 4 receptor deficiency: After adjusting for confounding factors, including external smoke exposure, physical activity, educational attainment (EA), participation in sports clubs or gym leisure activities, and Townsend deprivation index at recruitment (TDI), the MVMR analysis revealed that PM<sub>2.5</sub> levels maintained significant associations with pancreatic fat, HbA1c, and FGF-21.<h4>Conclusion</h4>Our MR study demonstrates conclusively that higher PM<sub>2.5</sub> concentrations are associated with an increased risk of obesity-related indicators such as pancreatic fat content, HbA1c, and FGF-21.