[jagraff]

I'm not sure if it applies to red meat, which usually has more fat, but certainly you'll starve to death if you eat only lean meat. It's colloquially known as rabbit starvation, because if you only eat rabbit and nothing else, you'll starve to death. Doesn't matter how many calories you consume - your body cannot process the calories, so you starve.

https://en.wikipedia.org/wiki/Protein_poisoning

[jononomo]

It does not apply to red meat generally. The larger an animal is the higher a percentage of fat it contains. A blue whale has 35% body fat, a cow is roughly 25% body fat, and a squirrel/rabbit is roughly 5% body fat.

Also, I render my own tallow from beef suet and often add it to ground beef. I also slow-cook roasts in tallow.