Olanzapine for Anorexia Nervosa

New analysis questions this antipsychotic’s use for weight restoration

STUDY: Alqurashi BF et al, BMC Psychiatry 2026;26:413

STUDY TYPE: Systematic review and meta-analysis

FUNDING: Independent

Background

We’ve tested nearly every type of psych med in anorexia, and none reliably restore weight. Olanzapine has some promising trials, and some negative ones, so this meta-analysis pooled the available randomized controlled trials to see whether it works.

The Study

• Seven randomized controlled trials, 152 patients total; trial sizes ranged from 15 to 50 participants.
• Olanzapine compared to placebo, chlorpromazine, or aripiprazole; dosing ranged from 2.5 to 10 mg daily.
• Duration and setting varied across trials; both inpatient and outpatient studies were included.
• Primary outcome: change in body mass index (BMI).

Results

The pooled analysis of four trials (91 patients) showed that olanzapine raised BMI by an average of 1.68 kg/m² more than control — a modest gain, and one that did not reach statistical significance (p = 0.19). Heterogeneity across trials was extreme (I² = 94%), meaning the studies were measuring something different enough that pooling them is hard to defend.

Psychological symptoms also disappointed. In the largest trial (Attia et al., 2019, n = 152), olanzapine raised BMI faster than placebo (0.259 vs. 0.095 kg/m² per month; p = 0.026), but obsessive-compulsive scores on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) were nearly identical between groups. Weight went up, but thinking didn’t change.

Practice Implications

1. Olanzapine can raise appetite, but anorexia is not just a disorder of low appetite.
2. Olanzapine carries risks that suggest caution in the face of these statistically negative results.
3. Though medications have failed, zinc has small positive trials for weight restoration in anorexia nervosa. It is low risk and addresses part of the underlying cause.