It's tricky...they definitely increase your appetite but they affect AMPK which is actually a metabolic regulator...AMPK changes a lot in the way the cell uses energy. AMPK in the periphery is actually good and that's what metformin activates but in the brain it has opposite effects increasing appetite etc.

At the same time they change your gut flora...so just some background if you take an overweight mouse and give its intestinal flora to a newborn mouse that newborn mouse will grow up fat even eating normal food. There are certain changes in the abundance of bacteria that are associated with this. Those same changes have now been seen in mice given zyprexa. So it really does make you gain weight beyond the calories your are eating.

Translational Psychiatry - Antipsychotics and the gut microbiome: olanzapine-induced metabolic dysfunction is attenuated by antibiotic administration in the rat

So based on what we know about the microbiota the best current way we have to change them is by changing the types of food you eat. So it's the basic eat healthy thing....lots of fruits and vegetables....anything with prebiotic fiber...so when Costello was on here about resistant starch that was interesting to me. Ideally we'll come up with a mix of healthy bacteria you can take orally but were not there yet. The only fast way to change flora is a fecal transfer which they only do for c. Dif infections right now. So the idea is it's not all about the calories so much as the content of what you're eating and how it affects the bacteria in your gut.