Wednesday, August 8, 2007

Glycemic Index Versus Load - Another Diet Myth

Yet another study confirms that diets composed of low Glycemic Index (GI) foods are better for both lipid management and weight loss. But, by only stressing GI they overlook the other half of the equation, Glycemic Load (GL). Put simply, it's not just how high the GI is of a particular food but how much of the high GI component is in the food product per gram or unit volume consumed.

GI is a measure of how quickly the carbohydrate portion of a food is converted to glucose and raises blood sugar. High GI foods raise your blood sugar rapidly and provoke a rapid and equally high insulin response. The body really hates this! However, GI is ONLY a measure of rate of change, not how much glucose/insulin is actually generated.

GL is a measure of the grams of carbohydrates in a quantity of food times its GI (divided by 100) and is a better indicator of how the body will respond to eating it. You can eat low GI food and still provoke a high insulin response if you eat enough of it. Similarly, eating small amounts of a high GI food may do little damage.

But foods are not composed purely of carbohydrates. There is another factor that must also be considered, carbohydrate density. For example, corn, and therefore popcorn, has a high GI. That would suggest popcorn is a food to avoid. However, popcorn is mostly air and does not contain many carbohydrates per unit volume. While the few carbohydrates in popcorn does indeed have a very high GI, you have to eat a fair amount to raise blood sugar.

Compare a cup of watermelon to a cup of high-fructose sweetened soda. Both have an identical volume. Watermelon also has a slightly higher GI than soda (72 versus 68). Yet a cup of watermelon has a GL of less than 1/3 that of soda simply because it is less than 1/3 as carbohydrate dense as soda. You are far better off consuming a cup of watermelon than a cup of soda even though watermelon has a higher GI.

I suppose if you are dealing with simpletons who cannot comprehend math or portion size you simply tell them to avoid high GI foods entirely. If you consider yourself a simpleton then just ignore this rant! Otherwise, pay attention to GL rather than GI.

Simply said,



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