In so-called early onset anorexia nervosa (AN), a rare and severe form affecting 8-13 year olds, experts recommend that, as soon as possible, treatment should take place on an outpatient basis, at an age when separation from the usual environment would be particularly unpleasant and deleterious. However, in severe AN, full-time hospitalisation (FTH) is still indicated when somatic and psychiatric instability criteria are met. Thus, the severity and rapidity of undernutrition in children aged 8-13 years suffering from AN (linked on the one hand to the frequency of total aphagia with refusal to drink and on the other hand to the lack of early detection of the disorder, frequently requires emergency FTH, contrary to expert recommendations. This FTH, which lasts on average 3 months in our specialized unit, has certain disadvantages: poor acceptability by the patient and/or his family, increased anxiety symptoms on entry and exit, school dropout, social isolation, coercive experience. In addition, the rate of premature FTH exits - before weight targets are reached - and the frequency of relapses after FTH remain high, making FTH unsatisfactory in terms of cost-effectiveness. Some families refuse FTH, which is classically long, exposing themselves to the risk of complications that can occur if the disorder is inadequately treated: somatic, acute and chronic complications; risk of progression to another eating disorder. In recent years, day hospitalization (DH) care has been developed for adolescents aged 11 to 18 years and adults (Madden, 2015). The few studies available are in favour of comparable efficacy, better acceptability and lower cost in the management of moderate AN compared to prolonged FTH, but also better social adaptation.In children aged 8 to 13 years with AN, whose somatic condition requires continuous monitoring in a hospital setting (the usual indication for FTH), a DH cannot reasonably be proposed immediately given the severity of the situation. Our hypothesis is that it would however be possible, in these children, to shorten the duration of FTH and to continue DH treatment once the critical period has passed at the somatic level, with comparable efficacy, best acceptability, best progress in terms of school and social integration, and lower cost.