Hello.The drug you say belongs to a group of drugs called neuroleptics. Many years ago, used neuroleptics had important side effects such as tremor, involuntary movements or cramps.With the introduction of new neuroleptics (for example that you say, olanzapine)improves these side effects but new neuroleptics cause increased sugar level, increased cholesterol or weight gain. It s difficult to find the perfect neuroleptic.In some studies, recently used neuroleptics ,such as paliperidone and aripiprazole ,have fewer side effects than olanzapine. About why the drug is done(olanzapine in this case), tell you that in most patients the positive effects of the drug outweigh the side effects. Besides the doctor who knows side effects prescribe the patient some effective measures such as diet and physical exercise. I wish you good health. (In case the answer would have been useful please indicate this)