Objective
The goal of this
investigation was to examine the effect of glycemic index on brain function
during the late post-prandial period (4-5 hours after eating a meal).
Methods
Twelve
overweight men consumed two liquid meals on separate occasions. The meals were
identical in calories, macronutrients, and palatability. The only difference
between the meals was that one had a glycemic index of 84, and the other had a
GI of 37. Brain activity was then measured by MRI four hours after consumption
of each meal. Blood glucose, insulin, and hunger were also measured repeatedly
during the post-prandial period.
Results
Plasma glucose
was significantly lower and hunger was significantly greater four hours after
the high glycemic meal when compared to the low glycemic meal. The high
glycemic preload also elicited a greater brain activity centered in the right
nucleus accumbens. This area of the brain is associated with reward and food
craving.
Comment
This is a
fascinating study! We’ve known for years that high glycemic carbs promote a
post-prandial dip in blood sugar that leads to an increase in hunger. I always
thought that this was governed solely by the endocrine system. This is the
first study to show that high glycemic carbs actually change brain activity,
particularly in areas that control reward and craving. While this is just one
study, it was very well designed.
Take Home Message
If you work with
me or have read my books, you know that a low glycemic approach is the key to
losing weight and improving health. This study provides even more reason to
strictly limit high glycemic carbs like bread, pasta, white rice and sugar.
Instead, focus on lower glycemic carbs like fruits, vegetables, legumes, and
whole grains. 
No comments:
Post a Comment