"But keep in mind also that if you're hunting or foraging you're probably going to need more than just 2,000 calories or whatever."

Yes, I guess thats why you don't go after mushrooms when you are hungry out there. (unless you also have oil)

Like the other one said: you want berries, seeds, roots, bark (if you have to), eggs, honey, .... whatever you find that gives you energy.

Mushrooms are a nice addition. Maybe also a medicin or alike, but never something you can live from.