The neuromolecular and metabolic underpinnings of Anorexia Nervosa (AN) are studied using multi-modal molecular (positron emission tomography with two different radioligands) and functional (functional magnetic resonance imaging) neuroimaging in a prospective design. Subjects with AN and normal weight adolescents will be studied with PET and MRI and followed for five years.

A total of sixty females (30 with AN, 30 healthy controls) are recruited into this prospective study. The subjects will undergo physical examination, body tissue composition measurement, functional and structural MRI of the brain and body, and positron emission tomography (PET) with ligands [18F]-FDG, and [11C]carfentanil. Subjects' weight and physical condition will be followed up for 5 years. The study will start in August 2020 and end in the fall of 2028.

Inclusion Criteria for AN:

1. Female sex
2. Age 18-32 3 years
3. BMI < 17.5 kg/m2
4. Currently fulfilling modified DSM-IV diagnosis of AN with or without amenorrhea, onset age before 25 years
5. Diagnosed less than 2 years ago

For controls:

1. Female sex
2. Age 18-32 3 years
3. BMI 19 20-25 kg/m2
4. No lifetime history of obesity (BMI ≥> 30) or eating disorders

Exclusion Criteria:

1. Any chronic disease or medication that could affect glucose metabolism or neurotransmission
2. History of psychiatric disorders (excl. AN for the corresponding study group)
3. Smoking of tobacco, taking of snuffs, or use of narcotics
4. Abusive use of alcohol

AN is more frequent in females, rare in males.

Totallly 30 female subjects with anorexia nervosa are recuited from the Eating Disorder Unit at the Turku University Hospital who meet the following criteria: i) modified DSM-IV diagnosis of AN with or without amenorrhea; ii) AN onset before the age of 25 years; iii) age between 18 and 32 3 years; iv) no lifetime history of binge eating. Their data are compared with 30 age and sex-matched healthy controls