This diet I find strange and maybe harmful for plain weight loss, but in the context metabolism antipsychotic medication, it makes perfect sense. The med changes a very little how fat is broken down, it basically does not alter how proteins are treated but it drastically changes how carbs are treated in the body. The meds (Mostly Seroquel and Zyprexa), create an imbalance in the system to do with insulin, and basically most carbs will not be used as fuel, it will just be stored as fat. The med prevents carbs from being used as fuel. Then it sounds wiser to eat more of those things the body actually will use as fuel.

Whether it also regulates appetite will probably vary between people, but I have a feeling that the fake starvation mode created by the med can also increase hunger, so getting the calories that can be burnt could at least in theory decrease hunger since the body now knows it's not starving.