Collier GR, Greenberg GR, Wolever TM, Jenkins DJ:
>Previous studies suggest that the rate of rise of the plasma
>glucose-dependent insulinotropic peptide (GIP) concentration, rather than the steady state
>level achieved, may be the stimulus of the increased insulin secretion
>that occurs when fat is ingested with carbohydrate. To test this hypothesis six normal
>men were given a 5-g iv bolus dose of glucose 15 min after a carbohydrate meal
>with or without fat. At the time of the iv glucose injection after the
>fat-containing meal, the rate of rise of plasma GIP was maximum, but the level was only
>40% of the achieved by 30 min. Plasma GIP did not change after the meal without fat.
>After the fat meal, peak insulin and C-peptide levels in response to iv
>gucose were 60% greater than those after carbohydrate alone despite similar peak
>blood glucose levels. The calculated insulin clearance was not altered by the fat
>meal. We conclude that glucose-stimulated insulin secretion is increased
>early after fat ingestion, possibly due to a rise in GIP or other incretins.

 -  The plasma glucose-dependent insulinotropic peptide (GIP) concentration
did not change after the pure carbohydrate meal yet the peak insulin and
C-peptide levels did - though 60% less than when fat was added.  This seems
to be contradiction to me.  How does GIP differ from insulin?

 -  It would be interesting to know how the six men were defined as
"normal" and what form the carbohydrates and fats were in.

 -  Adding fat to a carbohydrate meal slows down the breakdown and entry of
the carbohydrates into the blood stream.  I wonder to what extent the rise
in the insulin response that seems to be associated with adding fat to
carbohydrate is canceled out or overridden by the slower glycemic response.

Jean-Louis, I have enjoyed your recent contributions very much.

Best, Peter
[log in to unmask]