Association of olanzapine-induced weight gain with an increase in body fat

The goal of this study was to explore the pathophysiology of weight gain during treatment with olanzapine for schizophrenia.

The authors used a prospective, controlled, open study comparing body weight, body mass index, and related biological measures in mentally and physically healthy volunteers and olanzapine-treated patients with schizophrenia. Weight, eating behavior, leptin serum levels, body mass index, and body composition were assessed over an 8-week observation period.

A significant increase in body weight, leptin serum levels, and percentage of body fat was seen in patients treated with olanzapine, but the drug-free comparison group did not show any significant changes. The weight gain during antipsychotic treatment with olanzapine was mainly attributable to an increase in body fat; patients' lean body mass did not change.

In addition to the original finding that an increase in body fat is mainly responsible for olanzapine-induced weight gain, these findings confirm results obtained in other studies showing increases in body weight and serum leptin levels during treatment with second-generation antipsychotics.