On a diet consisting of nothing but protein, which of the following is the most likely outcome?

Question

(a) loss of weight because amino acids cannot be used for the synthesis of fat
(b) muscle gain because the amino acids will go directly into building muscle
(c) tiredness because amino acids cannot be used to generate energy
(d) excretion of more nitrogenous (ammonia-derived) wastes than with a more balanced diet

Answer 1

Choice (d) is the correct answer. Because ammonia is given off when amino acids are metabolized to yield energy but not when sugars and fats are metabolized, you would expect more nitrogenous waste to be excreted. Choice (c) is incorrect because amino acids can be converted into pyruvate and acetyl CoA and used to generate energy. If more amino acids are consumed than are used, the body will not store them as protein in muscle tissue but will instead store them as fat, so choices (a) and (b) are incorrect.