Interesting article in the 23 May, New Scientist. An investigation into the eating habits of animals suggest they naturally consume the correct ratio of different food types when they have free choice. Which led the investigators to believe that we all have not just the one appetite, but one per food type, and we try to satisfy each. But if the food available is unbalanced, then we eat whatever we need of protein as priority and tolerate either too much or too little of the other food groups as a consequence. It was suggested that the food commonly available to us western humans, these days, and our natural craving for the correct amount of protein, leads us to overeat on carbs and fat etc. in order to get that protein level.
I reckon we should be having a juicy steak every meal then.