. >> the hypothalamus, the part of our brain that controls our hunger, is pretty much shut off. so, they don't know that they're not hungry. >> reporter: do you ever feel full? >> no. >> reporter: never. >> no. >> reporter: are you hungry right now? >> yes. >> reporter: the wilkinson's lives are ruled by hannah's hunger. tonya keeps the kitchen on full lockdown, literally. a padlock on the refrigerator. no food in the cabinets. the pantry door always locked. >> i was cleaning the kitchen after dinner. we had just had a pot roast. she grabbed a huge piece of that pot roast and shoved it in her mouth. and i turned around and she was choking. i have caught her with the dog food, eating dog food. >> reporter: if she were left unrestricted in a room with food -- >> uh-huh. >> reporter: -- would she literally eat until she could not eat any more? >> she would eat herself to death. >> reporter: that kind of extreme behavior is not uncommon with those suffering from prader-willi syndrome. like mirabel rivera, featured in this documentary. locked behind this fence for her protection, mir

studies coming out that the hypothalamus is actually inflamed and scarred in many people who are obeseg we learn is high fat diets can cause that. what you are talking about is why people may become obese. >> that's what we are talking about here. i know we have to go. this is important. i'm sorry producers, i will buy them a hamburger. we are not blaming the people. you look at the portion sizes at restaurants. do we have a chance with what we are being served? >> maybe -- michelle obama, the first lady is making this -- we need to change our diet. should the food companies have responsibility for paying for your drug? >> i don't believe so. let's think for a moment. preventing your way out of a problem works if you don't have the problem already. treating obesity with dietary prevention and exercise is like putting sun screen on melanoma. people have established obesity they need treatments to get out of that. unless we wake up to that fact and understand what is at the heart of the problem we will not have an answer to that. why are one third of the population leaning in the face of