In a message dated 10/13/02 7:44:20 AM, [log in to unmask] writes:

>The glucose you make is made *on demand* in amounts
>proportional to that demand; the same cannot be said about the glucose
>you may eat.  The same point applies to the palmitic acid you make from
>glucose: it is released from adipocytes *on demand*, which is not true
>of the palmitic acid you eat.

The difference between the metabolic consequences of exogenous sources of
glucose and palmitic acid is their differential effects on the insulin
system. Remember Type 1 diabetics die of starvation if they don't get
supplemental insulin -- doesn't matter how much fat they eat.

Of course, too much glucose or too much fat storage can have deleterious
health consequences -- but it's not because either glucose or fat or palmitic
acid is unhealthy -- the fact of the matter is that the glucose we would have
gorged only in the warmer months would have been put into fat storage
(palmitic acid and some stearic); the fats we ate along with the carbs would
have been stored in whatever form they came in (that's how we get mixed lipid
profiles in our fat storage). Yes we can make MUFA from SFAs for the body's
use and if not used would be stored as MUFA. In the world we evolved in, we
would have laid down fat depots to be burned down in the winter. But now that
we've evolved culturally to a point that we indulge our instinct to eat carbs
to excess to put on a fat coat without having to face 'winter's reckoning',
we end up overfat and unhealthy. But it's not because we store or eat
saturated fatty acids in and of themselves. My point is that none of the SFAs
are unhealthy unless stored in excess.  I am not arguing that obesity is
healthy or doesn't have it's health consequences.

>>In particular, he thinks that if we are trying to burn body fat, which has
a lot of palmitic acid, and at the same time eating a lot of it, we are
simply getting too much.  This is why he recommends limiting saturated
fat *during weight loss* -- while one is burning one's own palmitic
acid.  This makes some sense from a paleo angle.  After all, we store
excess fat as an energy store for when we need it.  "When we need it"
would certainly be times when dietary fat is scarce -- so paleo man
would not normally be burning up large amount of  body fat at the same
time as eating lots of animal fat -- right?


The answer to your question depends on insulin.  If insulin is low enough,
one could eat fat at the same time as one burns it. Remember Type 1
diabetics. Pennington in the 1940s treated type 2 diabetics by giving them 2
pounds of fatty meat a day -- they lost gobs of weight and their diabetic
symptoms to boot. Peckwick and Kawan demonstrated the same thing in the
1950s. Unfortunately an extremely high fat diet is not that palatable.
I don't understand why Rosedale's so concerned with palmitic particularly.
Carbon length and degree of saturation both affect a fatty acid's burn rate
and at 16 C, palmitic would burn faster than 18 C stearic. Also palmitic
performs so many necessary functions in the body besides as a source of
energy -- most of the phosholipids that make up lung surfactant is palmitic
for instance. It is used all over in our membranes whether from de novo
synthesis or from our diet. Not enough saturated fat leads to flimsy
membranes. Enig says that the palmitic we eat often ends up as oleic after
the liver adds two more carbons and then desaturates. 20 -25% of human milk
is palmitic. Remember too that dietary fats are all mixtures of lots of fatty
acids -- olive oil even has palmitc acid (about 14%); beef and pork fat are
about 25%; chicken fat is about 23%. Also the percentage of our diet that
comes from SFAs (including palmitic) has been going down in the last 30
years, while the obesity epidemic rages.


Namaste, Liz
<A HREF="http://www.csun.edu/~ecm59556/Healthycarb/index.html">
http://www.csun.edu/~ecm59556/Healthycarb/index.html</A>