(X) Doubt
Last time I was in a medical space, intermittent fasting was all the buzz. The idea that it somehow has opposition from mainstream medicine seems like the kind of thing that an internet community would invent to pretend at being brave rebels (and run defense if case they were caught getting frisky with unsubstantiated health claims.) If you search "intermittent fasting" on google, the results are full of very positive articles from all the big names in medicine: Johns Hopkins: Intermittent Fasting: What is it, and how does it work?
Mayo Clinic: Intermittent fasting: What are the benefits?
Harvard Health: Intermittent fasting: The positive news continues
So no, I don't buy for one second that "most doctors do not believe something like fasting can improve health.""Most doctors" is an unspecific appeal to authority; which doctors can you cite that do not believe something like fasting can improve health?
"believe" was already mentioned by another commenter. An authority will make an assertion based on facts, not a belief based on ???
"something like" is it fasting or is it something else? Be specific.
"fasting" What kind of fasting do you mean? Between sunup and sundown like ramadan? Intermittent fasting? 30 day juice diet fasting?
"improve health" Improve how? And what aspect of health? "Health" is such a broad term that saying "this is good for your health" or "this food is healthy" are empty statements.
Versus believing something that came out last year, and has only single study sponsored by manufacturer...
Eventually if there's enough proof, the consensus shifts, regardless of how much initially people try to deny it
Fasting goes against recent consensus, yet it's becoming both more researched and more recommended (At the very least at the layman level, I'm no dietician)
* Something working doesn't tell you why it works, so it's important to be rigorous and always check, else you risk cargo-culting unnecesary or even risky things