For exemple

https://www.annualreviews.org/doi/10.1146/annurev-nutr-071816-064634?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub++0pubmed#_i24

16/8 is the most common intermittent fasting protocol for begginers. 20/4 is recommended in case of autoimmune disease, to reverse leaky gut and insulin resistance.