If someone is insulin resistant and uses fasting to help rebuild sensitivity (let's say a 1-meal-a-day approach), would their insulin levels really quickly become sensitive again, or would it adapt to these long fasting periods (and remain a bit insensitive)? Also--I feel like one could become more and more insulin insensitive (with increasingly bad dietary habits) but can it become TOO sensitive (VLC plus lots of fasting)? And would leptin react in similar ways?
I won't speak to insulin resistance, because I'm not sure about my past and present status other than I've never been officially diagnosed as a diabetic.
I'm sure I was leptin resistant when I joined this lifestyle last April but by the number of waist inches lost I think I'm cooking on all burners now.
To answer your question, my body tries very hard to adapt to whatever I do:
The only serious disagreement between me and my gut is that it refuses to tolerate my wheat habit any longer. Other items appear to be negotiable.
While your body is 'adapting' to fasting its tissues are becoming more sensitive to insulin. I honestly do not know if there are any clinical studies that can correlate adaption to fasting and sensitivity to insulin, or even if that is possible. Some things that are certain which pertain to your questions are this:
'Adaption' to fasting. Your insulin levels go down and glucagon levels go up and blood sugar stabilizes. Once much of the glucose in your blood stream and glucose in your liver is used up your body ups enzymes to release and burn triglycerides as free fatty acids. Also, your liver starts making ketone bodies primarily for fuel for your brain.
I think I see that one of your questions is whether or not a human will become more insulin resistant (insensitive) if fasting, and the answer is no, in fact, it works the other way around.
There is no such thing as being 'too sensitive' to insulin. In a depleted state, insulin sensitivity is a good thing, moving glucose into muscles, the liver and FFA into fat. As a person looses body fat, their body becomes better at nutrient partitioning.
You have to combine fasting with the right balance of foods for your body/blood type and also eat the right amount of carbs & exercise. OTOH Martin Berkhan the Leangains guy says insulin is well regulated. I hear people say all the time they can't fast because it "causes blood sugar swings" but this isn't my experience. As long as I eat paleo and use good sense with carbs I don't get a blood sugar response to food. The day after my meal I can be hungry a little depending on calorie/carb load but I find it goes away after a few hours. I do the Warrior Diet meal cycle of daily undereating/overeating.
Jack Kruse the leptin doctor says fasting is bad if you have leptin resistance but I disagree.
So in general no, I think fasting improves insulin because it helps lower it. You can't be "too insulin sensitive." Low calorie dieting doesn't make sense with fasting because you would constantly be hungry. Read the Warrior Diet and Eat Stop Eat by Brad Pilon. It's all about getting control of your blood sugar and hunger.
I just started fasting and a friend told me to look into insulin sensity too. Found this video on YouTube today http://www.youtube.com/watch?v=TKJXBTeBrgU&feature=colike
looks like fasting helps with insulin?