Introduction: Eating disorders affect mostly young persons, and may have important consequences on their mental and physical health. Objectives: To determine the probable diagnosis of eating disorders in medical students and to evaluate their associated factors. Methods: Descriptive and cross-sectional study performed in first-year medical students of a private university in Lima, Peru. An electronic survey was administrated to collect data of interest. Those students with a score= 20 in the Eating Attitudes Test-26 were considered to have probable diagnosis of eating disorders. For assessment of associated factors, we calculated prevalence ratios and 95 % confidence intervals using Poisson crude regressions with robust variance. Results: Of 440 first-year medical students, 375 (85.2 %) completed our survey. The prevalence of probable diagnosis of eating disorders in the study population was 10.1 % (11.3 % for females and 8.6 % for males). Associated factors to this variable were: school rejection due to nutritional disorders, job rejection due to thinness, social rejection of body image, family influence on body image, influence of fashion show models’ body image and influence of TV advertisement of slimming products. The two latter reached the highest prevalence ratio values. Conclusions: Around one in ten students has a probable diagnosis of eating disorders associated with family, social, work and mass media-related factors.