There's three main macronutrients to help make ATP: carbohydrates, fats, and proteins. And basically, anytime the body does something, byproducts are produced. The difficulty here with making energy out of a amino acid is you're left with the amino end, which is ammonia. This is then becoming a toxin, right? If it's that building up, exactly. You clean your toilet with this potentially all your floors. So luckily you have a liver,. so you throw this stuff to the liver, and it makes something for you called urea. It should be called BUN, not bun though. People get confused, especially if you're at a bakery.