Loren Cordain:
>>>We need to clarify our terms on this one. The ingestion of fat with
>>>carbohydrate results in lower blood glucose but higher insulin levels
>>>compared to carbohydrate ingestion alone (1,2).   Fat ingestion
>>>stimulates the secretion of glucose dependent insulino-tropic
>>>polypeptide (GIP) and it is thought that the additional rise in insulin
>>>is mediated by the effects of GIP (3).

I understand from the above that if carbohydrate is eaten alone the result
is higher blood glucose but lower insulin levels than when fat is added but
it is still not clear to me which of the two variables is the most important.

Jean-Louis:
>Remark: An earlier article [Lancet 2:454, 1966] shows that mixing glucose
>with tenderloin flattened the serum glucose curve but increased the production of
>insulin. The meat contained slightly more fat than protein (by calories). The
>author conjectured that there was a synergism between glucose with aminoacid,
>but the studies by Collier et al. show that the fat was the real culprit.

Interesting.

>Yes, but the articles mentioned show that despite a slower entry of
>carbohydrates into the blood stream, MORE insulin is produced.

Yet, the main function of insulin is to respond to rising blood glucose
levels.  If you come across an explanation in simple layman's terms of what
GIP is and how it interacts with insulin when fat is ingested with
carbohydrate, I would be very interested in seeing it.

>A 30/30/40 Zone meal produces the SAME effect on insulin than a 30/10/60
>low fat meal. Protein is neutral (on insulin). All of that suggest:

However, protein is very active on glucagon.

>1] Western meals are usually high in fat and carbohydrate. The co-ingestion of these two
> macro-nutrients, by inducing high insulin levels, may cause insulinresistance.

Intuitively, it makes a lot of sense to me, I just wish the science was a
little more clear.

>2] Barry Sears is wrong when he claims that, to keep insulin levels low, EACH
>meal should meet the Zone specifications. However, there are no good
>arguments against having 30/30/40 proportions on a daily basis.

For the sake of clarity Sear's recommended breakdown of macro nutrients is
usually referred to as a 40/30/30 distribution of carbohydrate, protein and
fat - not 30/30/40. He makes the argument that when adequate amounts of
protein is ingested at each meal, the body will produce enough of the
carbohydrate releasing hormone glucagon that will balance off the effects
of insulin's carbohydrate storing properties.  Also, according to some low
carb advocates another argument for not eating 40/30/30 is that if
carbohydrates are not eaten separately from fats and/or protein, levels of
human growth hormone will remain low.  It should also be made clear that
the 40/30/30 breakdown is a recommended starting point for some of the
people who want to loose weight on the zone. For active people who do not
need to loose weight, the zone might mean a 30/25/45 breakdown of macro
nutrients.

>Brief correction: the cited articles of Collier show that adding some fat
>to a carbohydrate meal actually decreases insulin levels -but only very
>slightly, much less than it decreases blood glucose levels.

With such conflicting results it seems that the jury is still out on this
issue.  I wonder which of Collier's studies on the effects of fats on
insulin levels are considered the most conclusive.

>Overall, it seems that the only advantage of combining fat and
>carbohydrate is that it stabilizes blood glucose levels, and satisfies
>hunger more; but the effect on insulin is almost zero, and moreover
>carbohydrate tolerance on subsequent meals is impaired.

If the effect is almost zero or even positive it is not clear to me why the
carbohydrate tolerance to future meals will be impaired.  Of course there
is the GIF factor but I doubt that more than a handful of very educated
scholars really understand the mechanism behind it.

A little confused.

Best, Peter
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