[fieldbob]

This is a function of higher mind; awareness, you have everything you need I would go with instinct. Science will never be able to explain how this works, just abandon all hope of scientific rescue. You have everything you need within.

[ch4s3]

You're describing magical thinking. As a counterpoint you can look at the problem of scurvy on per-industrial naval voyages. They didn't have an instinct to eat citrus, it was discovered by a long and painful period of trial and error. As another counterpoint, historically "rabbit starvation"[1] otherwise know as protein poisoning has been an issue periodically. If people innately felt the need to consume fat in particular this wouldn't happen.

[1] https://en.wikipedia.org/wiki/Protein_poisoning