Does weight loss affect olanzapine?

Possibly. Overdosing is a risk with this drug and metabolism is affected. Check with your prescribing doctor.
No. Side effect of Olanzapine is weight gain. So if you are trying to loose weight this might work against you. Also Olanzapine creates Insulin insensitivity so if you are diabetic need to be careful to prevent ketosis and hyperglycemic episodes.