Aim: To evaluate the relation between obesity and periodontal diseases on adults in Mansoura city, and the effect of individual dental and diet lifestyle on periodontal health. Methods:A convenient sample was carried among 150 adult patient aged from 35-44 years old visiting Mansoura dental training center. The patients were divided according to weight into 3 groups (normal weight, overweight and obese). Smokers, patients with systemic diseases, edentulous patients, pregnant and lactating females were excluded from this study. Body mass index (BMI) and community periodontal index (CPI) were assessed. The subjects were asked to answer a questionnaire to obtain information about diet and dental habits.  The periodontal health status and questionnaire were compared between the 3 groups. Data were statistically analyzed using SPSS version 21. Results:No statistical significant difference was found between the 3 groups regarding demographic data. The mean pocket depth and loss of attachment were significantly lower in group 1 (normal weight patients) than the other 2 groups. On the other hand, the questionnaire showed that group 1 consumed more balanced diet (P ≤ 0.001) than the other 2 groups. Group 1 suffered from gum diseases significantly lower than the other 2 groups. Group 1 showed significantly higher oral health compared to the other 2 groups. They also brushed their teeth frequently more than the remaining groups, also significantly higher number in group 1 used floss silk to clean their teeth. Conclusion:There is an association between obesity and periodontal diseases in adult patients. There is also relationship between obesity and oral hygiene. On the other hand, there is no relation between obesity and age, gender, education and occupation. Key words: Obesity, periodontal diseases, community periodontal index, diet and hygiene.