Getting such comparisons fully correct is certainly hard, but I don't think it goes the way you think it does in this case... looking at a few different specifi

Getting such comparisons fully correct is certainly hard, but I don't think it goes the way you think it does in this case... looking at a few different specific possibilities for "beef" and "grain", the "grain" looks to usually be nearly twice the calories of the "beef" per pound. Humans do not actually need huge amounts of protein and there is rarely a (medical) need to go out of your way to get protein no matter what your diet is.