This is going to get nasty. When you start questioning people's religious beliefs (and lo-fat IS a religious belief), you got a smackdown on your hands.
Because, it works, and if they admit that, they have to admit that they have been lying to us all along.
A natural diet consisting of mostly meats (with their attached fats) and vegetables is the way humans have eaten forever. If breads and sugars were natural foods, the metabolism would have no problem handling them. But as it is, a shot of sugar/flour spikes insulin (this includes today's luscious, hyper-fructose fruits), which in turn drives down blood sugar and causes lethargy and confusion quickly.
Meat causes little reaction from the pancreas, and fat causes virtually NO metabolic reaction from insulin. The body is composed of muscle and saturated fat. When it asks for these nutrients for repairs and growth, and I feed it sugar and grass, it can do nothing with these things but eliminate the fibrous one and store the other as fat, then ask for protein and saturated fats again. THIS is why the Atkins diet and others like it work...because when you give your body what it REQUIRES, it is not necessary to keep asking for these needs to be met continually, therefore, the appetite is suppressed in the proper way.