In fact, weight gain is quite common with olanzapine. For example, in one large scale 8-week placebo-controlled trial of olanzapine in bipolar depression, the olanzapine-treated patients gained an average of 2.59 kg., while placebo patients lost an average of 0.47 kg. Further, weight gain can continue over an extended period of time, mounting to an average of about 6 kg. over one year. It should be noted, however, that in prior studies, no efforts have been made to limit weight gain. More recent data suggest that interventions such as dietary counseling are effective in either preventing or reversing weight gain.