Statement of Problems: Numerous evidence indicates the deteriorating effects of obesity on body organs and its role in predisposition to systemic diseases such as diabetes. On the other hand, diabetes has been recognized as a risk factor for periodontal breakdown.Purpose: This study aimed to determine the relationship between obesity and periodontal diseases. The second aim was to clarify if periodontal diseases make the individuals prone to impaired glucose tolerance.Materials and Method: A total of 166 patients (age 35- 59 years) who sought dental care in Tabriz Dental Faculty were recruited in this study. Eighty three people had periodontitis in accordance with NHANES III index (test group) and the remaining who did not have periodontal disease served as the control group. The body weight (BW), height and waist circumference (WC) were measured in both of the study groups followed by fasting plasma glucose (FPG) and oral glucose tolerance test (OGTT). Data were analyzed by student t-test and Chi-Square followed by calculating the odds ratio and Spearman correlation.Results: All of the studied variables expressed a higher score in the test group than the control one ( p < 0.05). Evaluation of the correlation of obesity (OB), overweigh (OW), WC, and impaired glucose tolerance (IGT) with periodontal disease severity, revealed the highest correlation between OB ( r =1 and p <0.001) and the lowest between OW (r = 0.4 and p =0.07). Regarding the association of OB, WC and OW with IGT among women, the strongest association was found in OB (odds ratio, 6.5; 95% CI, 1.26- 23.6) and the weakest was in OW (odds ratio, 0.43; 95% CI, 0.07-2.6). These associations were similar among the males and the highest was between OB (odds ratio, 5; 95% CI, 0.82-19.41) VS. The weakest that was observed in OW (odds ratio, 0.39; 95% CI, 0.07-2.17).Conclusion: The association of obesity and periodontal disease is stronger than that with impaired glucose test. This may be attributed to different mechanisms involved in relationship between periodontal disease, obesity and diabetes.Key words: Obesity, Periodontal disease, Diabetes mellitus, Glucose tolerance