Final answer:
In a negative nitrogen balance, the body is breaking down more tissue than it is building. This is called protein catabolism.
Step-by-step explanation:
In a negative nitrogen balance, the body is breaking down more tissue than it is building. This is called protein catabolism. Protein catabolism occurs when there is insufficient supply of dietary proteins, leading to a lack of amino acids for cellular function and growth. Excess nitrogen produced during protein breakdown must be excreted as it is toxic.