If you read Good Calories Bad Calories you may remember that the Arctic anthropologist Vilhjamur Steffanson spent a year on an all-meat diet, with no ill effects. (In an earlier post about Steffanson, I stressed the fermented food that the Eskimos ate.) You may not know that animal fat was crucial for his health during that year, which began with a brief attempt to eat lean meat (meaning meat without fat):
On February 26, 1968, [Stefansson] was admitted to the ward and on February 28, started on the meat diet. At our request he began eating lean meat only, although he had previously noted, in the North, that very lean meat sometimes produced digestive disturbances. On the 3rd day nausea and diarrhea developed. When fat meat was added to the diet, a full recovery was made in 2 days.
During the year, he got about 80% of his calories from fat.
Via Inhuman Experiment.