The most efficient food is literally a brick of animal fat with some fresh nuts, berries, seeds, leafy greens for some vitamins and minerals. Doesn't get too much better than that, but it's hard to find healthy animals these days, and I hate killing even bugs.
Oh, and u can preserve stuff in fat prettty well for the winter.
BTW heres a cool fun link, u can rly use this info in a survival situation.
https://www.motherearthnews.com/real...s-zebz1305znsp