What Causes Weight Gain While On Zepsophrenia?

I have gone years without meds for zepsophrenia. The drug they used I could not tell any difference just weight gain. After being off it I lost all the weight and drop from Type 2 diabeties to Type 1. I also have parkinson. There is still to much stigma with this disease and the doctors don't spend enough time talking to you they just perscribe pills. I go fine until there is something threatening. I don't hear anything and I am not feeling like harming anyone or myself. I was on Invega Sustena. It was a very strong dose. I feel that the drugs are behind times as I have read that the drugs are worse than the disease.