I don't know how long it takes for insulin sensitivity to return to more 'normal' levels on a strict keto diet. I think it depends A LOT on the individual, the exact diet, how severe their insensitivity was to begin with blah blah blah......One thing I'm pretty sure of is that if you return to a "normal" american high carb diet after a spell of ketosis you can expect you insulin insensitivity to come back pretty quickly (and with a vengeance if you're an average female). In other words don't take on a CKD or ketogenic diet lightly if you haven't looked at and thought about the long term consequences. It may be a great means to drop fat in the short term (and look good in a bikini for the summer, or ripped for a show), but if you're interested in long term control of body fat then I feel you should rethink your options carefully. Read more, ask more questions etc.....In a nutshell I think that most people need to design a LIFESTYLE (as opposed to a diet) around minimizing glycemic/ insulin response. This could be "keto-for-life" for some folks, "lots of whole grains, veggies and beans/legumes" for other folks, and other intermediate options for some people. Of course if you're a hardcore bodybuilder then you'll want to go for that high GI/insulin response post workout. This is a great way to add muscle, but may not be optimal for loooong term health.