I'm not really interested in debating the merits of fasting in general. For things like dieting, general well-being, and some specific conditions, where there's some evidence to support it, sure, it might make sense for some people to try it depending on their circumstances. Most likely it'll work for some, and not others, but shouldn't do any harm provided it's not too extreme and there aren't underlying medical reasons that would make it dangerous.
But for specific conditions, like chronic fatigue ones, where people have found it made them worse, I will absolutely push back on glib assertions about the magic of fasting.
Because in those situations, it's not just that fasting may actually harm the individual, the perception that fasting is a solution can itself be harmful.
Because far from medical solutions being pushed, for years the standard treatment for CFS and ME in much of the world, including the UK, was graded exercise and Cognitive Behaviour Therapy (insert wild conspiracy theory about Big Physiotherapy and Big Therapy here).
The problem was, the evidence for it was shoddy and the experience of a lot of sufferers is that it just didn't work, and in many instances made them worse. That some people think it did work for them does nothing to negate the fact that for many it did not.
But the perception of those as the effective treatments meant the conditions were perceived as psychological, and that if people weren't getting better, well, that was on them for not trying harder. The condition was treated too often as not a real condition, and those not getting better from exercise and CBT as being at best depressed, and at worst, lazy.
Those guidelines have only just been changed here, and there's still debate about it:
https://www.bbc.co.uk/news/health-59080007
Pushing treatments with flimsy evidence as a solution can absolutely be harmful.
That's not to say there's no merit to someone saying, "I think this worked for me, might be worth considering?" That's one thing.
But saying, in response to evidence showing it made some people worse, that it must be a lie, that anyone saying that is in the pocket of the medical industry, and see, Gwyneth Paltrow says it works?
That's unhinged, and harmful.