All of these fads center around one fundamental trait: the sense of having control over your life. It doesn't matter whether they work; they sell you on the experience of "I'm successfully doing this hard thing to make myself better". And it just so happens that Silicon Valley is full of people who are addicted to the sensation of improvement. Eating disorders stem from the same psychological mechanism, just a differ…
I also wonder how much of it is people desperately trying to undo the damages of stress. What people might really need is shorter work weeks and more time off (including time away from social media and other non-work related stressors). But that's not something out culture really allows for or encourages. So we look to miracle cures so we can continue feeling productive.
The local community, where you’d buy your meat from your local butcher that had been in your neighborhood for 15 years, vegetables from the farmers’ market where the produce is all from within a 50 miles radius, where you go to church/temple/etc with the same faces every week, where the teachers and doctors that took care of you now take care of your children, etc, is pretty much dead.
What has replaced it? Amazon Prime, precarious contractor jobs, cheap replaceable crap brought in by cargo ship, startups claiming that they are just like “a family”. Of course this leaves a gap in people’s need for a sense of place and community. Of course it’s the perfect opportunity for charlatans who know how to tap into exactly that.