A BBC investigation in June 2008 found that this advice was being widely ignored by British doctors. Evidence suggested that the elderly are more likely to experience weight gain on olanzapine compared to aripiprazole and risperidone. Adverse effects
The principal side effect of olanzapine is weight gain, which may be profound in some cases and/or associated with derangement in blood-lipid and blood-sugar profiles (see section metabolic effects). A 2013 meta-analysis of the efficacy and tolerance of 15 antipsychotic drugs (APDs) found that it had the highest propensity for causing weight gain out of the 15 APDs compared with an SMD of 0.74. Extrapyramidal side effects, although potentially serious, are infrequent to rare from olanzapine, but may include tremors and muscle rigidity. Aripiprazole, asenapine, clozapine, quetiapine and olanzapine, in comparison to other antipsychotic drugs, are less frequently associated with hyperprolactinaemia. Although these drugs can cause transient or sustained hyperprolactinaemia, the risk is much lower. Owing to its partial dopaminergic agonist effect, aripiprazole is likely to reduce prolactin levels and, in some patients, can cause hypoprolactinaemia. Although olanzapine causes an early dose-related rise in prolactin, this is less frequent and less marked than that seen with haloperidol, and is usually transient.
Olanzapine was effective for treating the prodromal symptoms, but was associated with significant weight gain. References
External links

"Olanzapine". Drug Information Portal. U.S. National Library of Medicine. Alex B (5 January 2007). "Lilly Settles With 18,000 Over Zyprexa". The New York Times.