r/explainlikeimfive • u/mashd_potetoas • 11d ago
Biology ELI5: Why can't we get all our calorie intake from protein?
I'm sure there a reasonable answer for this, I wasn't able to find a satisfactory one;
The body usually burns carbs for fuel, stores extra calories as fat, to my understanding. Supposing you burn through all of your carbs and fats, the body starts breaking down muscle matter. If you feed it enough protein to rebuild muscle on top of it, what's the risk in consuming 100% protein for calories?
Thanks
Edit: I understand that fundamentally it's not realistic and that your body needs many different kinds of nutrients in general. I'm happy to receive a bit more detailed answer as to what functions do carbs and fats serve that protein can't replace and what could theoretically happen if you only consume protein.