Weight Loss in Anorexia Nervosa: Typical Rates and Medical Risks

Observed Weight Loss

In active restriction, patients may lose 1–2 lb (0.5–1 kg) per week, but rates vary widely based on starting weight, metabolic adaptation, hydration, and purging behaviors. Rapid loss (>2 lb/week) signals severe catabolism and high medical risk.

Medical Complications of Rapid Loss

• Electrolyte derangements (hypokalemia, hypophosphatemia, hyponatremia)
• Cardiac atrophy, arrhythmias, QT prolongation
• Refeeding syndrome (upon refeeding)
• Hormonal: amenorrhea, low T3, cortisol dysregulation
• Bone loss, lanugo, skin breakdown

Treatment Benchmarks

• Inpatient: Target 0.5–1 kg/week gain (refeeding protocol).
• Outpatient: 0.5 kg/week; weight restoration to >90% IBW.
• Multidisciplinary: Medical, nutrition, psychiatry, family therapy (FBT for adolescents).

Anorexia has the highest mortality of any psychiatric disorder. Early specialized intervention saves lives.