Background Omentin-1 is an adipokine, mainly produced by visceral adipose tissue that improves insulin resistance. Objective This study compared the serum levels of omentin-1 and insulin resistance markers in activeobese, inactive-obese and inactive normal-weight men. Methods In this cross-sectional study, 45 men (35. 0± 4. 2 years, no symptoms of illness) were assigned to active-obese (n=16, Body Mass Index (BMI)=28-33. 9 kg/m2 and 3-5 score in the Physical Activity level questionnaire (PA-R score), inactive-obese (n=18, BMI=28-33. 9 kg/m2 and 1 in PA-R score) and inactive normal-weight (n=11, BMI=18. 5-24. 9 kg/m2 and 1 in PA-R score) groups. Blood samples were taken from all subjects in fasting state to measure the serum levels of omentin-1, insulin and glucose. Also, Homeostasis Model Assessment Index (HOMA-IR) for insulin resistance was assessed. Findings The results showed that the omentin-1 concentration was significantly lower in inactive normalweight compared to the obese groups (P<0. 05). In the active-obese group, the glucose, insulin concentrations and insulin resistance index were similar to the inactive normal-weight group; however, these values were significantly lower than the inactive-obese group (P˂ 0. 05). No significant difference was found between normal-inactive and obese-inactive groups for glucose concentration (P=0. 079). Conclusion Based on these findings, it can be said that physical activity is more effective than obesity. Thus, the obese men can improve the negative effects of obesity on insulin resistance markers by performing physical activity and is not required to reduce the size of obesity.