Back in college, I worked as a "relief house-parent" in a group home for Prader-Willi "kids." In a nutshell, my husband and I would arrive at 3 pm Friday afternoon and stay until Monday morning. We prepared meals (according to each client's diet plan), did the shopping, supervised all activities, helped with personal hygiene issues, and dispensed medication, including insulin and anti-psychotics. We took them to the mall, took them to movies each Friday night, took them to the fair, etc. Our clients' IQs ranged from 32 to 80.  
 
Smacking a Prader-Willi kid for craving food is like smacking them for breathing--it's not a chosen behavior, it is what and who they are. Can they be maddening? You bet--they're prone to rage episodes, obsessive behaviors, self-mutilation, awful behaviors like rumination, and will do anything possible to get food--including climbing out a window at 2 am, sneaking across an alfalfa field, and breaking into a neighbor's garage to forage in a freezer and eat frozen, raw meat. Think about it--who would CHOOSE to gnaw on frozen, raw hamburger? It's not a choice, it's an inherent compulsion. 
 
My advice to anyone who feels they can't resist smacking/belittling/abusing their Prader-Willi child? Find a good group-home environment and place your child there with people who understand the disorder and can provide your child with the structure, training, supervision, and affection they need.  
 
Kris