- Objective: Obese patients demonstrate a variety of biochemical, metabolic, and pulmonary abnormalities. Inflammatory mediators such as tumor necrosis factor-α and interleukin-6 (IL-6) may have a direct effect on glucose and lipid metabolism. Hypoxemia in itself induces release of IL-6. The aim of this study was to examine the relationship between IL-6 levels in healthy volunteers (control group) and three different groups of obese patients: patients without obstructive sleep apnea syndrome (OSAS), patients with OSAS, and patients with obesity hypoventilation syndrome (OHS) (daytime baseline oxygen saturation of <93%). Research Methods and Procedures: We measured serum IL-6 levels in 25 obese patients (body mass index of >35 kg/m2) and 12 healthy women. Results: The results demonstrate statistically significant differences in serum IL-6 levels between the control group (1.28 ± 0.85 pg/mL) and obese patients without OSAS (7.69 ± 5.06 pg/mL, p < 0.05) and with OSAS (5.58 ± 0.37 pg/mL, p < 0.0005). In the patients with OHS, IL-6 concentrations were highest (43.13 ± 24.27 pg/mL). Discussion: We conclude that serum IL-6 is increased in obese patients. The highest IL-6 levels were found in the patients with OHS.