Cysteine is also an irreplaceable building block of vital proteins required to sustain life. It’s unclear if there is any potential benefit of applying these findings to the problem of human weight loss or fitness.
> Pepsin forms three between the sulfur atoms of cysteine residues in the peptide chain which hold important roles in the folding of the protein and stabilizing the two domains
[1] https://en.wikipedia.org/wiki/Pepsin
[2] https://biology.kenyon.edu/BMB/jsmol2021/Cat_Marko/index.htm...
I could be wrong, but I doubt it. Amino acid depletion sounds way more likely to be due to some kind of disruption in homeostasis rather than dietary intake.