The Glycemic Index

You probably fall into one of two categories:

1) You've never heard of the term "glycemic index." 2) You've heard of the term "glycemic index" (it comes up a lot in our chats) and you want to know what it is, thinking it may help you in your weight loss program.

Whenever you see the prefixes gly- or glu-, chances are someone's talking about sugar.

• Glycogen: the form of sugar stored in your muscles and your liver
• Glucose: the form of sugar floating in your blood
• Glycolysis: the process of breaking down sugar for energy
• Glucose tolerance test: a test performed by a doctor to look at your response to sugar

So if you deduced that the glycemic index has something to do with sugar, you're right. The glycemic index is a relative measure of how fast a given food raises blood sugar. Why that's important will be the subject of many future columns, and might just be the hottest topic in popular nutrition books (with good reason). The short version is this: When blood sugar goes up, the pancreas responds with a shot of insulin. Insulin is a storage hormone: One of its jobs is to escort the sugar from the blood into either muscle or fat cells. What we're now finding is that, important as insulin is, several things do and don't happen when insulin levels are high.

For one thing, the body doesn't burn fat. The faster a food raises your blood sugar, the higher the insulin response.

Got your attention now?

So, knowing just how fast a food you eat "breaks down" into sugar -- and thus how quickly it raises blood sugar levels, producing a high insulin response -- is crucial in weight loss. It's also one of the key areas where "us" and "them" don't agree. "They" -- meaning traditional medicine practitioners and dieticians -- tend to pooh-pooh that connection as unimportant. (I suppose they also ignore the documented fact that insulin signals the body to make more cholesterol, but that's the subject of a different column.)

Anyway, the glycemic index was developed to determine how fast a food brings your blood sugar up (which, incidentally, also contributes to mood and energy fluctuations). The people who developed it used pure glucose as a standard, giving it a rating of 100. The closer to 100 a particular food is, the higher its glycemic index.

Here are a few representative samples (some numbers vary because there are different versions of the scale):

Cherries: 25
Bananas (ripe): 60
Beans: 30-40
Rice cakes: 80-133(!)
Many processed breakfast cereals: 100
Nuts: 15-30
French bread: 95+

One food was a real standout, however. It's a complex carbohydrate, too, shooting to heck the theory that they are always slower-releasing and "better" for you. Want to guess what it is?

The bagel, which weighed in at 105. It beat the gold standard of pure glucose.

Now, the take-home point from this little academic discussion is not that high-glycemic foods are "bad" and low-glycemic foods are "good." In fact, high-glycemic foods are useful if you're on a college team and training twice a day and need the fastest replenishment of muscle glycogen stores.

But if you're trying to manage your weight, stay away. Go with the lower-glycemic foods as snacks. Eat the higher ones, if you must, with a little fat or protein to slow the response. Or avoid them completely for the time being, and begin to be aware of the powerful effect high insulin levels are having on your attempts to lose weight.

Anyone want to take another look at the "high-carbohydrate diet"?

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