On Sat, 5 Jan 2002, Adrienne Smith wrote:

> Why do you think Cordain assumes that most of our stored adipose fat
> is "saturated"?

If your diet is high in carbs, then if you store fat it will
mostly be from excess carbs.  A cow's diet, for example, is
high-carb.  When glucose is converted to fat, about 98% of it
becomes palmitic acid, a saturated fat.  That's not the end of
the story, however, since a good deal of that -- almost half --
is typically converted to monounsaturated fat.  This is why the
composition of animal fat is a little more than half SFA and a
little less than half MUFA.

> When we speak of grain-fed meat, for instance, we speak of
> its fatty acid profile being heavily weighted on the omega 6 side as
> opposed to grass-fed meats which has more omega 3s.

Keep in mind that the absolute amounts of these fats, the EFAs,
is very small, in the muscle meat of both feedlot animals and
wild game.  According to the USDA, the ratio of omega-6 to
omega-3 in beef, for example, is only about 2.5:1, which isn't
bad.  But the total amount of both is tiny.  It's about the same
in elk meat, but since the meat is so lean, the *percentage* of
EFA is somewhat higher.

But unless you're eating truly large amounts of EFAs, you
shouldn't really be storing much of it in adipose tissue, which
is also why meat has so little.  And if you are eating that much
EFA, you'll probably have other problems, related to the
oxidizing of these fats.  The organ meats, such as brain, have
more of these fats.

> Why doesn't each
> human's adipose body fat profile reflect his or her diet?  For example, if
> I eat mosty polyunsaturated omega 6 oil, wouldn't my stored body fat be
> mostly unsaturated?

If you're eating enough of this oil to store in adipose tissue,
then you're body fat would have more of it in it, yes.

> Also, I thought saturated fat burns "clean" while
> highly polyunsaturated fats such as flaxseed oil are more prone to
> oxidation.

It's not so much about how they burn as how vulnerable they are
to oxidation when they're not being burned.  The PUFAs are more
oxidation prone by far.

Cordain breaks down the fat composition of what he takes to be a
typical 2,200 kcal day (pp. 26-27): Total fat = 108g; SFA = 21g;
MUFA = 54g; PUFA = 21g. (4g of fat are missing)  On this plan,
SFA and PUFA are equal, but even combined they come to less than
half of the total fat.

Todd Moody
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