Let me reword that, he didn't totallllly denounce the idea.. but here's what he did say (You can find this quote around 9:57):
John Kiefer: Trashing Paleo, Ketogenic Diet Mistakes, Why It’s Good to Be Wrong - YouTube
Interviewer: "So let's talk about some of the stuff you were wrong about, the ones that were the most surprising for you in regards to carbonate or carb backloading that you thought was one way but is perhaps another?"
Kiefer:".…Eh…..that’s gonna open up a can of worms. So I'm pretty much convinced that the insulin hypothesis as it stands is totally wrong. Insulin is not the culprit that is causing issues…..and that came up because a lot of people actually made really good arguments about insulin release when you have other types of meals,it’s almost unavoidable ...because as you eat you get GLP1 (glucagon like peptide 1 - for unawares) Increase, which will make you release insulin, regardless. You have that and certain proteins have really strong insulin responses but we still see fat loss in those instances…..So I started looking deeper into it and insulin alone isn’t actually the main problem, it’s a combination of effects. It’s very distinctly insulin plus glucose. So in essence a very good Q is that high carb people make is that insulin levels are not always chronically elevated - it only happens once you’re sick and diabetic.
But part of the insulin and ketosis, you know insulin control in ketosis is the solution, part of their argument is that insulin is high all the time thats whats forcing extra nutrients into fat tissues and so on and so forth and causing insensitivty …..but...that doesn’t jive, it just, logically doesn’t make sense."