I thought there was psychological evaluation, and some time of...orientation? They're instructed about the new eating habits they'll have to take, and the patient has to indicate they're willing to change before surgery gets approved.  Which just shows these dumb fucks are liars who think the doctors are idiots for telling them shit like, "Hey you can't stuff your face anymore because your stomach can't hold much and if you try you'll just back up your esophagus until you puke and/or suffocate."