Remember, how large Atkins was when he died? He was having congestive heart failure and went off his "diet" because of it. He died because his health was is such poor shape when he fell.
That silly food pyramid is still valid. Our bodies *need* certain vitamins and minerals. If people just ate in moderation and ate less calories than they burned than we wouldn't need "diets". Ever hear of the "diabetic" diet? It's based on the food pyramid. The original Weight Watchers diet was based off it. It still works.
We are not carnivores. Our digestive system isn't made to deal with that much protein.