In this study, we investigated how cultural prejudices and social rejection may have a significant effect on obese women's dialogical self-development. Adopting a longitudinal methodological approach, we analyzed the developmental trajectory of three obese women along a period of two years, during which they were submitted to bariatric surgery to lose weight. The aim was to identify and analyze the configurations of their dialogical self before, right after, and months after the surgery. Some guiding questions were 'How did they position themselves at those three different moments? What were the social others and experiences that contributed to their dialogical self changes? What was the impact of imagined future 'selves' over their self positionings?' The research was based on both semiotic and cultural psychology and the dialogical self-theory. Results revealed important aspects of the dynamics of self-development, shaped by the cultural canalization power of prejudice. However, each subject, in idiosyncratic ways, used diverse strategies and reacted very differently to prejudice and weight loss experiences, which reveals the complexities of their dialogical self in constant processes of development.