OSFED — purging disorder vs BN and night eating (structured viva)

Formulation. Two OSFED-relevant patterns may coexist and both need naming: (1) purging disorder — recurrent purging to influence weight/shape without objective binge eating, not exclusively during AN; (2) features consistent with night eating syndrome — nocturnal ingestions with awareness, distress likely, not better explained as simple snacking. Carefully re-check binge fidelity (subjective vs objective binge) before excluding BN. BMI 23.5 does not exclude medical danger — potassium 3.2 already proves that.[1][2][3][6]

Differentials. BN requires recurrent objective binge + compensation; if true objective binges are absent, purging disorder is the better residual label than “almost BN — ignore.” Sleep-related eating disorder differs from NES by impaired awareness. Atypical AN needs significant weight-loss/restriction/AN psychopathology assessment. Organic causes of hypokalaemia and substance use should be considered in parallel.[1][3][5]

Medical risk. Treat hypokalaemia and obtain ECG now; dental review; stop unsafe purging with medical support. Normal BMI is irrelevant to purging toxicity.[6][5]

Treatment. Psychoeducation that OSFED is a real eating disorder. Offer CBT-E (transdiagnostic): regularised eating, monitoring, purge cessation plan, shape/weight overvaluation, night-eating pattern work (meal timing, sleep, alternatives to nocturnal ingestions). Guided self-help may be a step if mild and service model supports, but purging five nights weekly with hypokalaemia is not “mild.” Specialist ED referral. Fluoxetine 60 mg oral daily has strongest trial anchoring in full BN; if residual picture is BN-like after binge re-assessment or specialist judges medication indicated for binge–purge spectrum severity, discuss SSRI carefully — do not present it as an automatic OSFED licence. Never use bupropion in active purging high-risk ED states analogous to BN cautions.[4][5]