Can you help me understand the glycemic index?

Dear Dr. Sears,

I just started PACE last month and I’m trying to make sure I do everything exactly right. So far I think I’m doing pretty well, but I’m really confused when it comes to the glycemic index and glycemic load.

I thought I understood the glycemic index. Just pick foods that have really low scores. But now you’re saying that low GI foods could have big glycemic loads… and higher GI foods could have low glycemic loads. So where do I begin?

C.M.

Dear C.M.,

This is a great question and you’ll be glad to hear the answer isn’t nearly as complicated as you might think. In fact, once you understand the difference between these two measures, putting them together is easy. And they are critical to your weight reduction program.

You see, high glycemic foods can cause your blood sugar to shoot up very quickly. In response, your body releases insulin. And that’s bad news because the more insulin you release, the more fat your body will store.

This is where the Glycemic Index (GI) comes in handy. It’s basically a scale that ranks carbohydrates on how rapidly they cause your blood sugar to spike. I’ve been using this index at my clinic for years. And, when my patients stick with it, they often see amazing results.

But there’s another side of the carbohydrate story that’s missing…

While the GI tells you how fast foods spike your blood sugar, it doesn’t tell you how much carbohydrate you’re getting in these foods. The calculation for the GI doesn’t figure in how many grams of carbohydrates you would consume of a particular food. It considers the quality of the carbs but not the quantity.

This is an important distinction, because the amount of carbohydrates in the foods you eat also can have an affect on your blood sugar and insulin response. That’s where the Glycemic Load (GL) comes into play.

The GL gives you a “corrected” number that takes both the GI and the serving size into account. When these two measures are combined, it turns out that, while some foods may have a high GI score, the actual amount of carbs per serving is so low that the overall effect is harmless.

Take carrots, for example. They rate very high on the GI (92). But that number is based on comparing how fast carbs from carrots and an equal amount of sugar spike your blood sugar. So let’s say we wanted to compare eating 50 grams of carrot carbs to 50 grams of sugar. To eat 50 grams of carrot carbs, you’d have to eat about one and a half pounds of carrots! That means that each individual carrot has very few carbs, giving them a GL of only 1. So eating a carrot or two isn’t going to have much effect on your blood sugar.

And what about fruits? Cantaloupe and watermelon both rank high on the GI. But their low GL scores make them a nice treat when you want something sweet to eat.

Prunes are just the opposite. Taking only the GI (29) into consideration, they look like a good choice. But the GL tells the real story. Just one serving of prunes ranks a 34.2 on the GL.

Same with pasta. Most spaghetti, linguine and noodles have a relatively moderate GI. But with GLs in the 20s and 30s, these can be very fattening foods.

To find out how your favorite foods rank, check out the glycemic table on my website.

When used together, the GI and the GL work hand-in hand to help you make the best food choices possible to drop weight more quickly and keep it off.

To Your Good Health,

Al Sears, MD