Food intake is a motivated behaviour that consists of seeking, selecting and ingesting nutritional resources from the environment. Its main function is therefore, depending on these conditions, to ensure the supply, in adequate quantities, of the energy and biochemical substrates necessary for the proper functioning and need of the body. Thus, in addition to maintaining the body's fat mass level stable, dietary behaviour is part of the energy homeostasis system and is thus regulated and maintained by the central nervous system.

Although diet regulation involves several brain regions, the way in which these different regions communicate with each other and influence each other to orchestrate appropriate eating behaviour is not yet fully characterized. Among the structures of this network, the hypothalamus, a small structure (less than 1 cm3 in humans) composed of several nuclei such as the lateral hypothalamus, the arched nucleus or the lateral tuberal nucleus plays a crucial role.

The investigators propose to use ultra high field (7T) magnetic resonance imaging equiping the CEMEREM (CHU Timone, APHM, Marseille) to better characterize the role of this crucial small structure in food intake networks in order to better understand the impact of these structural and functional disorders observed in patients with anorexia nervosa and obesity compared to a control population without eating behaviour disorders.

Inclusion Criteria:

• No depression (HADS and BECK scores)
• No contraindication to 7T MRI
• Subject with with social insurance
• Subject who has signed the informed consent

For obese patients

• Body mass index > 30kg/m2
• Body diameter < 60cm (compatible with 7T MR scanner tube)

For anorexic patients

• mental anorexia according to DMS-V
• Body mass index < 17kg/m2

For healthy controls

• 18.5kg/m2\