I tried to include into ketosis into expensive tissue hypothesis by:
>> In a situation with close to zero carbohydrates (e.g. < 60 g carbohydrate
>> per day) as in starvation or when very few carbohydrates in the
>> diet are available, the brain can resolve its energy demand in about half
>> from fat, after a few days of adaption.
>

On Wed, 9 Aug 2000 07:43:59 -0400, Todd Moody <[log in to unmask]>
wrote:

>According to Lyle McDonald, the brain can adapt so that about 70%
>of its energy needs are met by ketones.  Thus, given your initial
>estimate of 500 kcal/day from glucose, after adaptation to
>ketosis that would be about 150kcal/day from glucose.

Todd, you are the one with personal experience with ketosis.
If *you* tell us 70% , I'd count this as a real reference.
I've to correct then:
"In a situation with very few carbohydrates available from food or body
reserves the brain can resolve its energy demand in up to 70% from fat,
after a few days of adaption"

I think ketosis doesn't make that much of difference for the
expensive tissue hypothesis and meat.
Because for any wild game (even rather fatty) the protein percentage of
energy in food is rather high and exceeding the 25% for the brain.
So even more than the glucose for the brain would be availabe anyway.
from protein (protein is converted to glucose, not to ketone bodies).

Ketosis, as you define it by test strips seems to mean that ketone bodies
*are* produced. This occurs when burning fat with simultaneuos high
gluconeogenesis (reducing the "normal" acetyl CoA pathway of fats).
This doesn't necessarily mean, that these ketone bodies are used in the
brain. Because,
if the total gluconeugenesis is so high as mentioned above (e.g. > 25%
of total food energy) then the brain has enough of direct glucose.
This questiones the 70% from Lyle, because you don't know how much gets the
brain or other tissue.
An active brain probably needs more than the resting 500 kcal btw.

A couple of very detailed details......

I can't imagine that the expensive tissue brain was enlarged in presence of
heavy gluconeogenesis instead of a few grams of fruit or tuber, even nuts.
The process produces ammonia which is toxic for the brain.

Or, here is a nice hypothesis supporting the "hunting only fraction".
Our brain *only* grew so big (initially), because of the necessity to retain
a fraction of the brain working in the presence of amounts of ammonia.
This theory works especially with pig-out periods of high protein and
gluconeogenesis alternated by ammonia detox phases...
Hunters piging out as father of all intelectuality.

I call it the ketosis induced brain enlargement hypothesis.
(alternate name: the huntes pig out into coma hypothesis).

Some would enjoy this.

Amadeus