To the OP:
The idea that insulin resistance, often a disease many decades in onset, could be significantly improved in such a short time span is medical hogwash that no one would say in front of an educated group of doctors. You would be laughed at, justifiably.....the ingredients for the "cleanse", which has never shown efficacy in cleansing much of anything but calories from your diet, is directly from "The Master Cleanse" of the late 70's. It is pure charlatan BS, in other words.
With that said, I use fasting and caloric restriction, all coordinated into cycles based on the starting insulin resistance and other CV factors, as a basis for treating metabolic syndrome. I believe, and am currently working on a scholarly paper to PROVE, that a big factor in our insulin resistance epidemic is more accurately called "glucagon deficiency".....in short, it is the result of often decades of 80-90% of a person's life that their metabolism is in a "fed state" vs fasted, with glucagon being chronically under-utilized. The premise behind my therapeutic approach is to slowly ramp up glucagon and its catabolic mechanisms over time, re-calibrating the relationship of insulin in the body, and thus slowly softening up the scary metabolic syndrome indicators.
So yes, fasting does play a role, but Kharrazian would get laughed out of the room if those opinions were ever voiced to an equally educated audience rather than Jimmy Moore.....sorry, them's the facts
"They now look to a single and splendid government of an aristocracy, founded on banking institutions, and moneyed incorporations under the guise and cloak of their favored branches of manufactures, commerce and navigation, riding and ruling over the plundered ploughman and beggared yeomanry." - Thomas Jefferson, 1826