Obesity is a condition when excessive adipose tissue accumulates in the body and that negatively affects health through predisposition to the development of many diseases and complications such as diabetes mellitus, cardiovascular disease, hypertension, and hyperlipidemia. Previous studies reported that obesity could influence the academic performance of the affected individual. Thus, we aimed in this study to measure the prevalence of obesity and its associated risk factors among medical students at Jazan University, and how it could affect academic performance.This is a descriptive, observational cross-sectional study that was conducted on medical students of Jazan University, Saudi Arabia, using questions that assess students’ demographic, academic performance and obesity. Data analyzed using t-test and chi-square test. We included 331 participants, most of them female (74%). About half of the participants have normal weight and recorded a high-grade point average (GPA) of 4 or more (out of 5). The highest GPA (4 or more out of 5) was achieved by 31% of students with normal weight, compared to 12% of underweight, 8% of overweight, and 5% of obese students. Being non-obese is associated with a higher GPA. Further, a significant relationship was observed between obesity and GPA (p-value= 0.013), in which obesity has a negative impact on the GPA of the affected students.In conclusion, our study showed that the medical students at Jazan University with normal weight achieved higher GPAs than other weight groups. We also found that food consumption is increasing with stress in overweight and obese students. This result highlights the importance of prevention measures and awareness to improve academic performance among affected students as obesity has well-known complications.