Eating from nose to tail means getting lots more fat than you would if you only ate the muscle, because bones and organs have a lot of fat. Or so I read in many paleo articles/threads. Bone marrow is essentially all fat. But organs?
A serving of the heaviest organ, the liver, has 20 grams of protein and only 4 grams of fat
The heart has the same ratio, 5:1 protein to fat
Even the fatty fat fat brain has an equal amount of protein as fat
Except for the brain, organ fat is pretty much all omega 6 fat.
The total mass of bodily organs is much less than 10% of total body weight, so the animal is providing us with lots of muscle, and much less organ and marrow.
Am I missing something? The fat content of organs looks to be almost exactly the same as meat we usually eat, or less if your meat is grain-fed. As a disclaimer, I know nothing about offal, so there may be a big hole in this reasoning.
From what I've seen, most organs are generally understood to be high protein, not high fat, and are more often touted for providing nutrients that may be lacking in muscle meat. Vitamin A in liver, for example. The degree to which the organs are cooked influences the vitamin content, of course.