Ha! Yes, excess of vitamins that are not fat soluable will be peed out, but all 3 macro-nutrients will be converted in to fat in calorific excess. You can get obese from eating too much protein too, it just happens less as protein is more expensive and more filling.
Pretty cheap and easy to down a pint of oil and sugar, go over your calorific needs, and still be hungry an hour later.
Also, there are essential proteins and essential fats. There is no such thing as an essential carb. And before you possibly pull the old "Brain needs glucose!!1" trick, there is a little thing called gluconeogenesis.
I was aware of the bodies various emergency conversion of protiens to sugars, but I thought the particular type the created was not consumable by the brain.
Besides, those mechanisms are last resort emergency processes designed for when you are starving, practically dying and atrophying your own muscle protein. Trying to use them to avoid eating carbohydrates is ludicrous and potentially dangerous.
What is it people have with carbs? Is it the obesity crisis that is fueling the rejection of them? A normal diet should get most or all of it's energy from carbs and fats. Protein is for tissue and cell construction. I hear all manor of non-sense about sugar rushes and carb crashes, with people not understanding how long the buffer chain of energy is in the body and just how tightly regulated your blood sugar actually is, it does not swing around that much if you are healthy. It's almost as non-sense as people suggesting some food make your blood more acidic. Your blood being even a tiny fraction more acidic is a serious condition and very, very dangerous.
Also, I was not aware that excess protein can or will be converted to fat. Recent articles I have read surrounding the influx of "Protein enhanced foods" suggests that anyone with a normal diet including some meat and fish will already have excess protein to the order of twice the recommended requirements. Also, that eating excess protein, without going overboard has little to no ill effects. The short is, you DO NOT need extra protein unless you are embarking on some serious muscle building training.