Objectives Given that many university students engage in unhealthy lifestyle choices that can lead to overweight and obesity and that the same students often have poor quality of life (QoL) metrics, we aimed to search for a relationship between QoL and body mass index (BMI) among first-year medical students enrolled in a Peruvian university. Materials and methods This was a cross-sectional convenience sample study. It consisted of 150 first-year medical students who were generally healthy. The BMI and QoL of the participants were measured using a health scale and the Short Form-36 (SF-36) QoL-validated questionnaire translated into Spanish. Results The participants consisted of 89 women and 61 men, with a median age of 19 years. Sixty percent of students were of normal weight, and 13% were obese. BMI weakly predicted SF-36 score, R= 0.035, F(1,148) = 5.39, p = 0.022, β = -0.72, p = 0.022, α = 86.78, p < 0.001. This correlation was mostly driven by the physical functioning and general health aspects of QoL. Conclusions A small, but statistically significant, negative correlation exists between BMI and SF-36 scores among the study participants, indicating that obese first-year students had lower QoL than their normal-weight counterparts. This suggests that nutritional intervention among first-year students may improve QoL in subsequent years of their university career.