pzo:

I suspect higher FBG on VLC is an adaptation.  A "normal" carby diet will feature substantial periods during which BG is elevated (the post-prandial state).  But since BG never rises meaningfully on VLC, FBG will usually rise to compensate in order to keep the average BG reading close to where it would be on a carby diet.  (This probably has something to do with the fact that gluconeogenesis can't up- or downregulate very quickly.)  It's my current working hypothesis, anyway.

Is this a problem, in the long term?  I don't know. 

It would be interesting to compare A1C levels in the two situations.  But just like the mainstream confusing ketosis with ketoacidosis, I suspect there's a difference between a Type 2 diabetic whose FBG is 110 on a carb-heavy diet that also regularly spikes to 200+, and someone on long-term keto whose BG is always 110, fasting or no.  (See: the difference between "insulin resistance" and "physiological insulin resistance.")

Re: resistant starch, here's the thing about messing with gut flora via PS.  Everyone likes to quote the "more bacteria in your colon than cells in your body", etc.  The corollary to that is that the possible diversity of gut flora is also monumental -- which means that the response to additional resistant starch will be strongly individual. 

For instance, I fart hugely at any more than 1 TBS -- and, more importantly, I start becoming strongly demotivated after 3-4 days at any dosage.  It's not depression, but it's a total lack of motivation to actually do anything, along with a lack of sex drive.  My hypothesis is that the typical bacteria that feed on RS also produce serotonin (something like 2/3 of the serotonin in your body is produced by your gut bacteria).  The observations I've seen, including my own, are consistent with excess serotonin: serotonin is a precursor to melatonin, which would explain the improved sleep some people get, but excess serotonin also results in the same sort of mental and physical state produced by SSRIs: low motivation and zero sex drive.  (Interesting article.)

The responses vary widely.  Some find the BG-lowering effects of RS persist for months, some find they disappear after a few days.  Others notice no effects at all from RS.  And so on.  My point is that RS is being sold as a panacea that everyone is deficient in -- and when the American Gut Project baldly states outrageous bullshit like "6-month-old Hadza kids that are being weaned onto food are getting 100 to 200 grams of dietary fiber a day, every day" (an absurd claim that has gone unchallenged by anyone), I have trouble taking them seriously.

Anyway, yes, IF does very well for some people.  I'm glad you're one of them!

JS

La Frite:

Yep.

sylvie:

Note that I didn't say IF isn't a good idea for reproductive-aged women!  I said that I've observed that a substantial number of them don't seem to do well on the classic 16/8 regimen.  I don't know enough endocrinology to speculate as to why, but I offer the following observations:

1. A good metric for whether IF is a good idea for you is whether you can do it without feeling like you're starving.

2. You don't have to IF every day.

3. Therefore, if you're really hungry for breakfast one day, eat it!

4. Skipping breakfast isn't the only possible plan.  If scheduling permits, I know people who have success with a big, hearty late breakfast once they finally get hungry in the morning (~10 AM), skipping lunch, and then eating dinner normally.

5. A spoonful of coconut oil can sometimes help get you through a rough spot (i.e. you fasted and maybe shouldn't have, but can't get to real food for another few hours).

I think part of the problem might be that women are so used to restrictive diets that always feeling hungry is shrugged off as the price of not being fat.  It's easy to starve yourself into a low thyroid state with that mindset.

JS

P. Winter:

I'm not sure they're alternative theories: I suspect they all contribute. 

The advantage of even a few ounces less weight on the feet is well-known: thus, racing flats.  So a genetic variation that results in a lighter foot and lower leg would be quite an advantage, especially as distances increase.  Such a build would not generate the most power over short distances, though, which is why we don't see any Kalenjin sprinters.

The article is also correct that mental and physical toughness can create a margin of victory: at the highest levels of any sport, the margin between winning and losing is tiny differences.  Cue the great American distance runner Steve Prefontaine:

"A lot of people run a race to see who is fastest. I run to see who has the most guts, who can punish himself into exhausting pace, and then at the end, punish himself even more."

"Somebody may beat me, but they are going to have to bleed to do it."

There's a lot of interesting discussion to be had about the survival value of initiation ceremonies, but it's well beyond the scope of a single comment!

JS

Ana:

There is solid literature on fasting improving cancer outcomes.  (Important note: adequate protein intake is generally protective against getting cancer: it's only if you already have it that protein restriction and fasting are helpful.)  Fasting can also improve a host of infectious conditions, which is likely why our appetite usually decreases when we're sick.

I see no evidence for there being any process of "detoxification" beyond the benefits of fasting.  The benefits of "cleanses" and other restrictive diets generally come from the degree to which they approximate fasting -- and you'll receive more benefit from simply not eating than you will from any protocol involving juices, maple syrup, lemons, or any other magic plant extract.

(Note that I don't oppose juicing, if that's how you like to consume vegetables...but there's no need to consume pathological amounts, and they're not a substitute for food.)

Autointoxication, as far as I can determine, is complete quackery.  You can search for pictures of these hypothetical "diseased colons" full of "mucoid plaque" and however many pounds of old poop are supposed to be stuck in there, because colonoscopy is very common now and they ought to be easy to find.  

You won't find them, because they do not exist.  

Frankly, people worry too much about their poop.  If it's brownish, doesn't hurt as it comes out, and is mostly solid, you're probably fine.  The obsession with regular bowel movements has no scientific basis that I can find, and generally traces back to 19th century religious fundamentalism (more).

Caveat: you can't out-cleanse or out-fast a bad diet.  It's much easier to not accumulate fat  and medical issues than it is to get rid of them!  That's why my approach to food is simple: when I'm eating, I eat like a predator.  Otherwise, I don't eat.  

That being said, there are exceptions like candidiasis (for which carb restriction can be helpful), kidney stones (drink more water), gout (avoid fructose and alcohol), and GERD (stop eating grains and fermentable carbs, start drinking a bit of vinegar).  But those are each entire articles in themselves!

JS