You.
I am not a fan of gurus; lots of people here will suggest particular experts, but to me, listening to Dr. X or Dr. Y is just a good starting point.
IMHO, we should look at various sources of information about fasting, check the research ourselves to the best of our ability, then make an informed decision.
So whoever you decide to listen to, you shouldn’t take their statements as gospel.
Mark Mattson, Ph.D. and teacher at John Hopkins university. He is a neuroscientist and has been discussing/teaching/studying fasting for the past 25 years.
There are some YouTube videos that you can easily access to listen to him speak on fasting.
The documentary “Eat, Fast and Live Longer” featured Michael Mosley visiting Valter Longo, Mark Mattson, Krista Varady and Luigi Fontana, all of whom discussed research that all points to the potential benefits of fasting.
Additionally Jason Fung, Prajit Jamnadas and Satchin Panda are all worth looking up.
Peter Attia (MD) and Rhonda Patrick (Phd in biomedical science and nutritional health) are reliable sources, I watch their interviews to stay motivated. They give a lot of useful information about fasting and general health advice.
Is this even a question…? Cole robinson (snake diet). Hands down. Guy lives and breathes fasting and no one else is as passionate about the subject or attempts to spread the message to the capacity he does. Im sorry but all these other answers are trash. As he would say, im not going to debate with any “fat pigs” either (all love).