The only "science" I have read regarding eating only meat and fat is in regards to raw feeding dogs, however, common sense dictates to me that the same applies to humans. Meat, fat and bones alone are not a balanced diet for a carnivore. Organs must be included and not just liver. A wild carnivore will eat virtually everything including soft bones, marrow and the tripe (stomach lining) and all the partially digested plant matter and microbes clinging to it. So do the aboriginal peoples who consume this type of diet, and they also ferment a lot of game for storage. One can assume (and it is highly emphasized amongst raw feeders) that there are many essential nutrients for long term health that are found in these items. I do not believe humans can achieve long term health by eating only meat, fat and occasional liver.