There is no established definition for the concept of long-term eating disorders , with only partial consensus regarding the duration and set of unsuccessful treatments received, giving rise to the concept known as severe and persistent eating disorder (SEED).

We speak of a SEED when:

• An eating disorder with more than 7 years of evolution is presented, with neurobiological impact due to prolonged malnutrition and loss of social capital.
• At least 2 evidence-based treatments have been received, with an evolution of more than 3 years.

There are a number of common patterns in people who have a severe and persistent eating disorder (SEED):

• They have established patterns of food restriction.
• They have deeply ingrained anorexic cognitions (rigid thinking about weight, shape, food; persistent anorexic thoughts and feelings, often accompanied by ritualistic behaviors; dichotomous thinking style).
• Personal identity intertwined (confused) with AN (fear of change without AN, anorexia as the only value in one's personal identity, anorexic ideology).
• BMI less than 17.7 (low BMI from adolescence to adulthood).
• Chronicity understood as "resistance to change": history of previous treatments with few results, people who have not requested treatment, years of illness.
• The seven years of the disorder appear to be a turning point in treatment: those who have received specific treatment and have not improved may need a different approach, a change of goals, and a reconsideration of expectations.
• Especially after 10 years of the disorder's evolution and after having tried several treatments without success, it is considered a long-term eating disorder (LTD).
• Perfection as a compensatory mechanism. A strategy that protects them from a near absence of self-esteem: setting such cruel goals makes them feel superior and balances feelings of inadequacy.
• Feelings of inadequacy lead to a need for external validation, heightened sensitivity to criticism, and a high degree of reactivity to social approval. All of these factors pose difficulties in developing an internal identity and a degree of autonomy.
• Dichotomous thinking style leads to the adoption of rigid and inflexible rules.