The investigators are conducting a randomized controlled trial using an adaptive design for adolescents (ages 12-18) with anorexia nervosa to compare standard Family Based Treatment (FBT) to adaptive FBT with an Intensive Parental Coaching (IPC) component. If participants do not reach expected milestones by session 4 of treatment, participants may be randomized to receive additional IPC or continue treatment as usual with regular FBT.

Potential subjects aged 12 to 18 with anorexia nervosa (AN) will be recruited from Stanford University, University of California, San Francisco, other bay-area medical programs and clinics, and online advertisement to the population at large. If participants are deemed eligible, participants will be invited for a baseline interview (about 2 hours in duration) during which the investigators will conduct interviews and collect questionnaire measures. Then, participants and participants' families will begin Family Based Treatment (FBT) with a study therapist at Stanford University or University of California, San Francisco, respectively. All assessments and treatments are conducted through tele-health.

At session 4, if participants have not gained 2.4kg, an indicator of early treatment response, participants and participants' families will be randomized to receive either treatment as usual (FBT) or an adaptive form of FBT, during which families will receive additional Intensive Parental Coaching (IPC). If participants have reached weight milestones (i.e., 2.4kg at session 4), participants will continue FBT as usual.

At 3 months of treatment and end of treatment, the investigators will collect the same measures taken at baseline. The investigators also ask that families participate in 6- and 12-month follow-up, respectively.

Inclusion Criteria:

• 12-18 years of age and living with participants' families
• meeting DSM-5 criteria for AN (both subtypes) except for the amenorrhea requirement
• medically stable for outpatient treatment according to the recommended thresholds of the American Academy of Pediatrics and the Society of Adolescent Medicine.

Exclusion Criteria:

• associated physical illness that necessitates hospitalization
• psychotic illness, mental retardation, or any other mental illnesses that would prohibit the use of psychotherapy
• current dependence on drugs or alcohol
• physical conditions (e.g. diabetes mellitus, pregnancy) known to influence eating or weight
• previous FBT
• currently taking medication for co-morbid disorders that cannot be safely discontinued on a stable dose for less than 2 months
• in the case of patients with current, or a history of sexual or physical abuse by family members, perpetrators of the abuse will be excluded from treatment.