By the way, protein remaining the same isn't really true. Your actual protein needs fluctuate based on what your diet is and what you're doing.

Carbs are, for instance, protein sparing. This isn't a real concern if you're not training fairly hard, but if you ARE training hard, and you reduce carbs, you might need to kick up the protein.

And so on. You need a certain amount of glucose for your brain, for instance. Your body will produce this, mostly from protein, so if you're at like zero carbs and trying to, for instance, gain muscle, you'd need more protein to do it than you might if you were eating more carbs.

For the average person, a ballpark protein is probably fine, but that's not quite the same as protein needs being static.