Lot's of things that are beneficial for most people can be detrimental to others. Lots of people get great benefit from going on silent meditation retreats whereas for some relatively few others such silent meditations retreats can trigger a psychotic episode. The fact that IF can be harmful for some people prone to eating disorders does not mean that it is harmful to the majority of people just as the fact that a silent retreat might trigger psychosis in some people does not mean that it is not beneficial to many people.