The prevalence overweight and obese among children and adolescents increases gradually in the world and became an epidemic in both developing and developed countries. Overweight and obesity in the adolescent period are the main risk factors contributing to the development of cardiovascular diseases in the adulthood period. This study was planned to reveal the prevalence of obesity and association of healthy lifestyle behaviors with obesity in adolescents. Methods: This research was carried out 859 students studying at Istanbul Hezarfen High School between the dates 1 February to 31 March 2017. The general dietary habits and night eating statuses were determined using the Mediterranean Diet Quality Index (KIDMED) and Night Eating Questionnaire (NEQ) and anthropometric parameters such as height and body weight were measured. Results: The mean age of the students was 15.9 ± 1.3 years. Of the students, 19.2% had overweight, 13.7% had obese BMI values. In this study, 32.4% of all students had low and 13% of them had optimal nutritional quality. The difference between two genders was statistically significant (p<0.05). The Night Eating Syndrome was not present in 78.9% of all students whereas it was detected in 21.1% of them. Conclusions: In our study, there was no statistically significant relationship between obesity, adherence to Mediterranean Diet and Night Eating Syndrome.