According to the phenomenological perspective, the lived body disorder is a core feature of feeding and eating disorders (FEDs). Persons with FEDs experience their own body first of all as an object looked by another person, rather than coenaesthetically or from a first-person perspective. In particular, the main features of this disorder are: alienation from the own body and from the own emotions, disgust for it, shame, and an exaggerated preoccupation for the way in which one appears to the others. Phenomenological research has recently highlighted that the gaze of the Other plays an important role. Because persons with FEDs cannot have an experience of their own body from within or coenesthetically, they need to apprehend their own body from outside through the gaze of the Other. This way of apprehending one's own body when it is looked by another person is called by Sartre the 'lived body-for-others'. Normally, the constitution of one's own body, and consequently of one's own Self and identity depends on the dialectic integration between the first-person apprehension of one's body (lived body) that it is based on coenaesthesia, and the third-person one, that it is based on the sense of sight (lived-body-for-others). When the dialectic is unbalanced toward the pole of the lived-body-for-others, experienced from without, the symptom occurs. Starting from these clinical observations, the so-called Optical-Coenaesthetic Disproportion model has been developed. In this paper, we describe this model, its philosophical and clinical foundations, and finally its clinical implication and its relationship with other disciplines, i.e., neurosciences. Level of evidence: V.