Why does everyone think having done IF means you can skip the prep phase?You're still using carbs for fuel.You haven't down regulated FAS.In the book Kiefer says that if you're at a very low body fat (>10%) or doing DB, you can skip the prep phase. Later it has been said that having done CNS or another ULC diet before may enable you to shorten the prep. Depleting your glycogen stores quickly is another method of shortening it.Where did the IF idea come from?
People just trying to be lazy/not wanting to go 10 days without carbs :-P.You know everyone always wants instant gratification -- trying to get the results in the shortest amount of time humanly possible.
I don't recall anyone saying prep phase can be skipped, just that you don't loose much, if any weight during the prep phase after switching from IF. Which is likely due to being somewhat glycogen depleted already. So if someone is saying it can be skipped, that's likely where the confusion is.