Background: The prevalence of obesity is growing in Chile. The personal perception about the own nutritional status is associated to the risk of obesity. Aim: To analyze the personal perception about their nutritional status among adults living in Santiago and to compare it to the objective diagnosis obtained according to Chilean Health Ministry norms. Material and methods: The body image was explored in 735 people between the ages of 20 and 90. The weight and height were obtained under standard conditions, and the body mass index (BMI) was calculated (kg/m²) and classified according to the criteria of the Health Ministry. The concordance and Kappa index between both criteria in function of age, gender, nutritional status and height were analyzed. The model that best explained the weight subestimation was determined with multivariate logistic regressions. Results: Fifty two percent of subjects classified correctly their nutritional status, 30% subestimated, and 18% overstimated the nutritional status (Kappa 0.27). The multivariate analysis showed greater subestimation in obese (OR 5.8 95% IC 4.2-7.9), in men (OR 4.5 95% IC 2.7-7.3), people younger than 60 years old (OR 2.0 95% IC 1.3-3.1) and people of small stature (OR 3.1 95% IC 1.9-4.9). Conclusions: Half of the studied subjects had an inadequate perception of the body image. Educative campaigns are needed to reinforce the concept of adequate weight. This may contribute to promote health and reduce the risk of obesity