Objective: Obesity is an important risk factor of atherosclerosis and its prevalence in humans is increasing. Recent studies suggest that the leptin and adiponectin play important roles in obesity, and they are associated with complications of obesity. However, the mechanism of effects has not been outstandingly established. In this study, we studied leptin and adiponectin levels according to body mass index (BMI) and their relationship with oxidative parameters. Methods: A total of 87 healthy individuals with BMI >35 kg/m2 (n=29, Group 1), BMI=25-35 kg/m2 (n=29, Group 2) and BMI <25 kg/m2 (n=29, Group 3) were included in the cross-sectional observational study. Leptin, adiponectin levels, total antioxidant capacity (TAC) and total oxidant status (TOS) were measured. Oxidative stress index (OSI) was calculated using TAC and TOS values. Statistical analyses were performed using Chi-Square, Mann-Whitney U, one-way ANOVA, Kruskal-Wallis, Pearson correlation and multiple regression analyses tests. Results: Age and gender ratio were similar in the groups. The TAC level was the lowest in group 3 and the highest in group 1. The TOS level was higher in groups 2 and 3 than in group 1 (p <0.05 for both). OSI levels were similar in groups 2 and 3, and it was significantly different from the group 1 (p<0.05). The trend for leptin levels was decreasing and for antiponectin levels was increasing from group 1 to group 3. Except for other parameters, levels of leptin were independently related to the TOS (b=-1.123, 95% CI=-12.734-0.255, p=0.040), OSI (b=1.689, 95% CI=1.105-12.481, p=0.018) and waist circumference (b=-0.592, 95% CI= -0.630-0.134, p=0.003). Adiponectin had no significant relation with these parameters. Conclusion: Findings of the present study reveal that leptin decreased and adiponectin increased with BMI in healthy people. These data support that these changes may be responsible in the increased TOS and OSI levels.