Eating disorders (ED) are a multifactorial pathology. In their origin multiple variables are involved to which nowadays a possible enhancing factor is added: the diffusion and promotion of the culture of thinness and the apology of ED through the social media (SM) used by the youngest people. Through the feedback tools of the social networks (likes, comments, visits, retweets, etc.) and the elements of comparison between equals of the most visual SMs, many users come to develop risk behaviours that in turn give feedback to others. In addition, a sense of belonging to a group or tribe is created through communities whose members feel supported and where very restrictive diets are shared in an affective way, as well as ways of hiding these and other behaviours from those who do not belong to the group; both elements make it difficult for professionals and the family to intervene. Due to the extensive use of SMs, the rapid dissemination of all that is published, and the limited control over shared content, it is virtually impossible to control those sites that advocate and promote behaviours that contribute to the development or maintenance of ED. Cyberbullying or intimidation through digital technologies often uses body image criticisms that damage the self-esteem of the most vulnerable. This cyberbullying is a factor increasingly present in young people who have suffered an ED. The key to prevention is considered to be media literacy in the use of SM, as well as parental supervision of the youngest. People at risk or who have already been diagnosed with ED find in these networks the social support they seek but are biased towards risk behaviours, when it is possible for health professionals to use them to the benefit of promoting healthy habits and for recovery from these disorders.