Background &Objectives: Available studies on obesity in Eastern Mediterranean Region countries indicate that obesity has reached out an alerting level among both children and adults. Factors associated with the occurrence of obesity have not been well investigated. The purpose of this study is to investigate the effect of lifestyle factors in obese male and female university students in Jeddah, Kingdom of Saudi Arabia. To explore the relationship between obesity and PA of young youth in KAU and to investigate differences due to gender. Material & Methods: A number of 91 adult students (48) of the surveyed parsons were male, with about (52.7%), while the female were (43), with about (47.3%) their age ranges from18-26 years from KAU attending the University in 2011-2012 completed a self-administered questionnaire, including providing correct self-reported data on height, weight and PA. The study conducted cross-sectional analysis of the correlation between obesity, defined as stated by KSA standards, and measures of physical activity and inactive behaviors (exerciserelated PA; walking, running, biking, moderate and vigorous activities self-defense, weight training, housework and other activity) adjusted for age, sex and matched in relation to a range of personal characteristics.  Results: There was a significant difference in the t tests according to obesity level in physical activity steps counted by the pedometer monitors (P=0.046). The P-value for the t tests (according to gender) for Min Walking =0.021 < 0.05; that is a significant difference (towards male); for min jogging =0.004 < 0.01; that is a highly significant difference (towards male), for min vigorous activity = 0.012 < 0.05; that is a significant difference (towards male), for min weight training =0,006 < 0.01; that is a highly significant difference (towards male) and for distance =0.037 < 0.05; that is a significant difference (towards female). Majority of participants (51.6%) were skip meal sometimes. One fourth of the students skipped breakfast, drink soft drinks seven times per week, and only eat fruit once per week. Significant differences in the PA levels of youth were evident with regard to gender. The present study has demonstrated that the occurrence of PA among KAU students is relatively high. Therefore, there is a need to the stages of PA adoption and support by university and public policies to encourage active living and discourage sedentary habits