Have you ever watched "Alone"?

After watching the survival show, you'll come to realize that fat reserves make all the difference between withering away and sustaining oneself.

Even with ample grams of protein, the absence of fat leads to rapid weight loss (consider also that the assimilation of amino acids necessitates fatty acids).

Here's a knowledge nugget to chew on: The human brain is around 60% fat, with 25% to 30% being saturated fat.