I'm finding it almost impossible to lose weight, because i'm taking olanzapine. why does the drug increase weight so badly ?

Several reasons.: Sometimes it affects your energy level and you don't get as much exercise. Sometimes it increases appetite, too. It is crucial to count calories, so you don't exceed the calories you need daily, or you will gain weight. Cut your calories by 100 a day and you will lose 1 pound a week. Walk a mile and you will burn 100 calories. It's a numbers game. Know what you eat. Count condiments even.