Objective: To analyze the differences in body adiposity determined by the Body Mass Index (BMI) and the Circumference of the Waist (WC) according to age groups in university students of both sexes. Material and method: 330 university students, 152 male and 178 female, from a University of the Central Zone of Chile, were evaluated. Three groups were formed according to age (18 to 20 years, 21 to 23 years and 24 to 26 years) and the prevalence of overweight and obesity was determined according to BMI and WC. Results: In women, both for BMI and WC there were no significant differences between the three age groups. In men there were no significant differences in the three age groups by BMI, however there were differences in WC, since the group of 18 to 20 years had lower WC than the other 2 age groups (p <0.001). According to sex and WC, a higher prevalence of overweight and obesity was observed in men (p <0.05). Based on BMI, there were no differences between both sexes (p> 0.05). Conclusion: WC appears to be a more accurate indicator than BMI, since it reflects significant increases in abdominal obesity at older ages, at least in male university students, although more confirmatory studies are needed.