Question: how long do you have to fast to increase growth hormone?
Answer: One study found that 3 days into a fast, HGH levels increased by over 300%. After 1 week of fasting, they had increased by a massive 1,250% ( 18 ). Other studies have found similar effects, with double or triple HGH levels after just 2–3 days of fasting ( 19 , 20 , 21 ).