Problem Statement: Today, immobility and resulting weight gain constitutes one of the greatest problems among young people. The greatest problem for individuals spending a lot of time on the Internet is immobility. The result of this status is spending less energy than the amount required daily. Immobility is considered a cause of being overweight, and being overweight creates a vicious cycle by leading to further lack of mobility. Purpose of Study: The purpose of this research is to investigate the relationship between the level of problematic Internet use (PIU) among Turkish university students and their body mass indexes (BMI). Methods: The study sample consists of 525 university students studying at different departments (Elementary, Fine Arts and Turkish Language Education) at Fatih Faculty of Education at Karadeniz Technical University during the 2010-2011 academic year. Participants were selected through stratified sampling. Accordingly, in this study the departments were determined randomly from Faculty of Education. Distribution of the sample by gender was 234 males (44.6%) and 291 females (55.4%). The mean age of the students was 21.8 (SD = 0.72). Racial distribution of participants was homogenous. Questionnaires were administered to students in groups, in a class environment, by the author. Participation was voluntary. In total, six hundred students participated in this study. Seventy five of them had to be excluded for not responding properly to all questionnaires, so the final sample consisted of 525 participants. Findings and Results: The results indicate a significant relationship between BMI and PIU. A significant difference was determined between the students' BMIs (moderate or severe weakness, normal, weight, semi-obese and obese) and their PIU levels. Levels of PIU in those with obesity-level BMIs were found to be higher than the other groups. Conclusions and Recommendations: These results reveal that the use of communication technologies such as the Internet has a number of negative consequences for university students. In respect to the duration of students' daily Internet use, students may benefit from having to plan how and when they will use the Internet, in order to limit how frequently they use the Internet and to use it effectively.