Background <p>Obesity and overweight are widespread among individuals in both developed and emerging nations. Obesity is a global health issue, and its prevalence has been increasing in Egypt for several decades. The health belief model (HBM) is a comprehensive framework model that has an important role in preventing disease and promoting health.</p> Objectives <p>This study aims to measure the prevalence of overweight and obesity among medical students in the faculty of medicine at Ain Shams University and to determine the effect of nutritional educational program on body mass index and health belief model scales among them.</p> Methods <p>This study was conducted in the Faculty of Medicine at Ain Shams University among medical students in 2 phases: phase 1, a descriptive cross-sectional study to calculate the prevalence of the disease; and phase 2, an intervention study that included a sample of 100 medical students whose body mass index was greater than or equal to 25. The study tool is a self-administered questionnaire based on the health belief model for weight control behavior that is tested by the participants before and after the intervention program.</p> Results <p>Most participants had a normal BMI, while 40% were overweight or obese. There was a statistically significant difference in the HBM scores before and after the intervention sessions. The mean BMI before the intervention was 29 ± 0.25 and had improved after the intervention session to 29, where there was a highly statistically significant difference (<i>p</i>-value &lt; 0. 001).</p> Conclusions <p>Nutritional education sessions based on the health belief model help in improving the knowledge and habits of high-risk medical students for weight gain. There were substantial changes between before and after the nutrition program interventions.</p>