Because of the placebo effect, all you really need for anything that’s not outright poison to have a positive effect on average is a convincing enough practitioner. Ideally people have narrow criteria for judging that, but it’s just so ripe for exploitation, every scammer can try a different tack, and some are bound to slip through.

IMO, the solution is a system of tight regulations on the definition of medical advice and the qualifications required to dispense it. I can also see that this one specifically would be hard to legislatively prevent without training and licensing yoga teachers, for example.