What is the optimal period of water fasting to produce the most HGH?

I found many studies about HGH production during water fasting:

First study says that 24 hour or 1 day fasting produces 2000% increase in HGH.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC329619/

Second study says 3 days of fasting increased HGH by 287% in men.
https://www.ncbi.nlm.nih.gov/pubmed/773953

Third study says 5 days Water Fasting caused an 300% increase in HGH and 40 days Water Fasting 1250% increase.
https://www.dietdoctor.com/fasting-and-growth-hormone

I thought that if I do more days fasting I can produce more HGH but this studies are confusing.