The following web page of the North American Association for the Study of
Obesity (NAASO) 2000 Annual Meeting provides some interesting information on
the validity and value of the "glycaemic index" which is used by many folk
who are attempting to control weight gain and diabetic reactions to
carbohydrates.
<http://www.medscape.com/Medscape/CNO/2001/NAASO/NAASO-01.html>
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Obesity in the New Millennium: Highlights from NAASO 2000
M. James Lenhard, MD
The Debate Over the Glycemic Index
During the last several decades, researchers have sought to move beyond
measuring carbohydrates as "simple" or “complex." The glycemic index (GI) has
been used in research settings, and some have argued that it should be
applied in clinical settings as well. Two prominent researchers debated
whether it is important to consider the GI of foods in the diet and its role
in body weight regulation.
Taking the side in favor of the GI was David S. Ludwig, MD, PhD, Director of
the Obesity Program at Children's Hospital in Boston, Massachusetts.[4] Dr.
Ludwig began his presentation by defining the GI. It is a measure of the
rate of carbohydrate absorption from a meal. More formally, it is the area
under the glycemic curve after ingestion of 50 g of carbohydrate of a test
food divided by the area under the curve following ingestion of 50 g of a
control food.
For example, white bread (a "simple" carbohydrate) causes a large rise in
glucose after consumption and would be assigned a GI score of 100. A piece
of processed whole grain bread does not cause as large a rise in glucose
levels and would be assigned a much lower GI score. He reported some of the
conclusions from more than 100 published scientific studies. Most of these
studies found beneficial effects of a low GI diet. Studies have suggested
that consuming a meal with a high-GI food results in less satiety and more
postmeal eating compared with a meal with low-GI food. A 12-week crossover
trial in humans showed significantly greater weight loss in the subjects
consuming low-GI food. One proposed mechanism for this is the greater primary
(postprandial) insulin release that is caused by food with a high GI, which
may contribute to greater weight gain.
The case against the GI was debated by F. Xavier Pi-Sunyer, MD, from the
Obesity Research Center at St. Luke’s/Roosevelt Hospital Center in New York
City.[5] Although he acknowledged the potential utility of the GI in some
research settings, he questioned its role in any type of clinical setting.
He pointed out that there are factors that influence the GI of a food,
besides the food itself. For example, the method of preparation, the
acidity, and the other foods that are served with it influence the GI.
For example, the GI of boiled cubes of potatoes rises 25% simply by mashing
them. Allowing a banana to ripen by only an extra day or 2 can almost double
the GI. Dr. Pi-Sunyer indicated that, even in carefully controlled studies,
the variability of the GI (measured as the coefficient of variation) can be
as high as 30%. There are also individual differences in the postprandial
glucose rise. Using the GI only, a cola may be preferable to bread, and candy
may be preferable to potatoes.
Finally, he questioned the notion that high-GI foods lead to obesity. Many
populations that eat a large quantity of high-GI foods, such as Southeast
Asians, have significantly lower body weight than populations who consume a
lower quantity of these carbohydrates.>
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Dr Mel C Siff
Denver, USA
http://www.egroups.com/group/supertraining
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