ABSTRACT Objective The aim of this study was to evaluate whether the depiction of a fat body for health communication on the Instagram social network by the national societies governing obesity management present elements that enhance weight-related prejudice, with the slim body as a reference. Methods We investigated the last publication quintile, totaling 2,155 publications. A total of 72 images were included and 99 bodies were decoded. The bodies were classified according to positive and negative characteristics into four categories (body presentation, clothing, food and moving behavior) in which the negative characteristics have the potential to enhance the prejudice. The chi-square test was applied to test the difference in the proportion of bias elements associated with body weight between the fat body and the thin body. Results The fat body was more represented (p≤0.05 for all) headless (32.3% vs 9.2%), with bare abdomen (17.6% vs 0%), with a focus on the abdomen (11% vs 0% ), with tight clothes (32.3% vs 0%), sad expression (23.5% vs 6.1%), involved with food of low nutritional value (14.7% vs 0%) and in sedentary behavior ( 11% vs 0%) compared to the thin body. Conclusion National societies that govern management of obesity presented the fat body with more negative elements that enhance the prejudice associated with excess weight, which is an important public health problem.