Excretory Products and their Elimination

Urea is the main nitrogenous waste of humans. It is formed in the liver by the ornithine cycle from the ammonia produced by the deamination of amino acids.
The main source of these amino acids is the protein taken in the diet; excess amino acids cannot be stored and are broken down.
A person on a long hunger strike takes no protein at all, so very few amino acids are available for deamination.
The body first uses its stored glycogen and fat for energy, and tissue proteins are spared as far as possible.
As a result much less urea is formed in the liver and less urea is excreted in the urine.
Blood glucose does not rise during starvation; it tends to fall. Amino acids are normally absent from urine, and sodium excretion decreases because there is no intake of salt.
So the person will have less urea in his urine.