Thanks for the dialogue also. I know next to nothing about the details of
instincto eating and it's instructive to hear it first hand.

Just to finish off -

G:
>>It's good to keep in mind that you can get into ketosis withoug necessarily
>>dropping carb intake extremely low. All that's required is sufficiently
>>high energy expenditure.

K:
>So as long as the carbs eaten are burned that day (so to speak) the body
>remains in ketosis? I thought ketosis is when you are burning fat and/or
>protien for fuel.

Your body will preferentially (though not exclusively) use carbs as its
primary energy source. If your activity level is high enough, you can
deplete your carb reserves (glycogen) sufficiently over the short term to
switch into almost exclusive fat burning, producing ketones = ketosis. You
also need protein during ketosis both to generate glucose (gluconeogenesis)
and to provide certain TCA cycle intermediates necessary to run fat
breakdown (beta-oxidation).

K:
>What happens to carbs eaten when a person is in ketosis?
>(My ignorance of this is pretty complete ;))

Theyll be burnt for energy. If you eat enough, your metabolism will switch
back to carb burning and the enzymes necessary for ketosis will return to
baseline levels = leave ketosis.

I don't have a good idea at all of what goes on when you traverse the
ketogenic threshhold back and forth. There are so many questions. Exactly
what happens and in what order? Can one "adapt" to such transitions?
Exactly what variables defines the threshhold level? How do different
people differ in their threshhold? Can this level be (intentionally)
altered over time? Can all people adapt equally well to ketosis given
enough time, or are there some for whom it will simply not work well no
matter what?

G:
>>The relevance of ketosis to hunter gatherer groups
>>is a point I'm quite intersted in. In fact, I find the whole process of
>>ketosis fascinating. It's quite a dramatic shift in metabolism and
>>undoubtedly involves changes in the regulation of several genes.

K:
>I am quite fascinated as well--especially after experiencing it as a normal
>thing--i.e. outside of fasting. I suspect I was well on my way to burning
>out from a too high carb diet (excess raw fruits living in the tropics for
>6 years). But ketosis is very pleasurable I find.

I've never tried ketosis, but am tempted to just for the experience. I get
the anecdotal impression that *if* you adapt successfully, it is perceived
as an enhancement in terms of well being. On the other hand, there are some
who do not see it this way, but I'm concerned that they may not have given
it enough time or done it quite correctly (e.g. eaten optimal protein:fat
ratio). There may also be increased levels of testosterone accompanying
increased basal levels of cholesterol (such as were observed with
Stefansson and Anderson). This could well contribute to "feel good"
feelings. Some people on keto diets report dramatically *lowered*
cholesterol levels, however.

G:
>>I get the
>>impression that ketosis is generally thought of as a sort of back-up system
>>for the body when sufficient carbs aren't available, but I wonder about
>>this. To the extent that certain hunter gatherers were predominantly meat
>>eaters (depending on locale), ketosis might have been the predominant - and
>>perhaps ancestral - energy-generating metabolic pathway for that group.
>>Another point of interest is that the body goes into ketosis during
>>fasting, a state that is relevant to surviving famine and that can be
>>considered the limit for the longevity-enhancing (in animals) process of
>>caloric restriction.
>
>I'd guess you are right on all counts. Though as a species we are
>incredibly adaptable to various diets, I suspect that the major difference
>between our metabolism and the rest of the primates is the addition of a
>ketosis metabolism evolved alongside the increased percentages of animal
>foods in the ancestral diet. Who knows though, maybe a chimp easily has the
>metabolic ability to deal with a paleo diet. I'd love to see a primate
>study where they are given only animal foods and low carb plant stuff:
>would they thrive like humans do? Or are we evolutionarily unique in our
>ketosis abilities? Perhaps every mammal has the ketosis mechanism ready and
>waiting--since it is basically the fasting mechanism...

Yes, you raise another interesting question I'd like to know about - just
how widespread in the animal world is what we call ketosis? I'm sure other
animals can carry out beta oxidation of fats, but does that mean they can
generate the equivalent of ketosis? So much reading to do, so little time.

>>K:
>>>While
>>>ketosis is probably useful for us switching from high carb diets, is it the
>>>goal of paleodieting? How many of the listers here figure they are in
>>>ketosis most of the time?
>>
>>Good questions. My impression from the book is that Neanderthin hovers
>>right around the ketogenic threshhold and could go either way.
>
>How does it go for Neaderthinners when they pig out on fruit or carrot
>juice even, or don't they ever do that?

I certainly won't speak for Neanderthinners, but I do know that severe
consequences have been reported by some when they do things like that. It
should be taken into account that many also have problems handling "normal"
levels of carbohydrates.

G:
>>and b) whether your protein intake might be
>>lower when you eat those avocadoes than when you eat the meat.

K:
>Yes. Definitely. Great point! So the implication is that the proper
>digestion of fat "needs" a complimentary protien eaten with it (as is found
>in animal foods).

Yes, this is very definitely true if you're in ketosis. Just how critical
the ratio is, and what the consequences of eating above/below your
"optimal" ratio are pedrtinent questions.

K:
>This solves a query I have had for nearly a year about
>the merits (or lack of) fruit-fats (avos, olive oil) and the way they
>"stand-in" for animal fats. I could gain weight with avos, but have been
>losing a little with the very fatty meat and marrow. I doubt that
>paleo-humans had much of these fruit-fats available (except maybe nuts
>which have plenty of protien--though I wonder if folks could get fat on
>them as well?)

It's probably also an important point that as well as less protein,
avocadoes have a fair amount of carbohydrate (8 oz avocado = 3.6g P/12 g
C/30 g F) relative to meat (4 oz porterhouse steak = 28.2 g P/0 g C/25.1 g
F). You might be in ketosis with the meat but probably don't get there with
the avocadoes.

G:
>>On a mixed food diet, if you eat an amount of fat significantly in excess
>>of maintenance requirements, you will store the fat and gain weight. I
>>presume this also has to happen even on a keto diet, but that it's much
>>more difficult to accomplish.

K:
>By mixed I assume you mean grains, or would you consider fruits the same
>way (as just more carbs)?

No, by mixed I meant plants + meat = non-ketogenic vs only meat = ketogenic.

Best,

Gary