In order to understand the glycemic index, you first must understand this very important fact: not all carbohydrates are created equally. Some carbs contain fiber and are digested very slowly, while others are straight up sugar and are digested very quickly. And not only are they digested differently, carbs affect our blood sugar levels in different ways as well. Some carbs can cause an immediate spike in our blood sugar while others seem to work to balance out our blood sugar levels. So never forget: not all carbs are equal.

The second principle of understanding the importance of the glycemic index is to understand this simple fact: your blood sugars matter. High blood sugars are a precursor to type 2 diabetes. Type 2 diabetes is a significant health concern that can cause amputations, blindness, kidney failure, and obesity. In fact, it’s the seventh leading cause of death in the U.S.

Glycemic Index: What Is It?

Glycemic index indicates how a particular food (because of its carbohydrate content) will affect your blood sugar. The smaller the number on the glycemic index, the less the food will raise your blood sugar, and vice versa. But the glycemic index is also about the quality of the carbohydrate, not just the quantity. For example, a slice of 100% whole grain bread has a glycemic index of 51, while a slice of white bread has a glycemic index of 71. Both are considered as one serving of carbohydrate, however, the whole grain bread is a “better” carbohydrate than the slice of white bread.

According to the Mayo Clinic, glycemic index is generally divided into three categories:

55 or less = low glycemic index or “good” carbohydrate

56 – 69 = medium glycemic index

70 or higher = high glycemic index or “bad” carbohydrate

Harvard Health Publications has an extensive list of foods and their assigned glycemic index that’s worth looking through and understanding. As you’ll see, refined or highly processed foods usually have a higher glycemic index than foods that are less processed and found in nature. But that’s not always the case. Every now and then, I’m surprised by foods and their glycemic index value. Take, for instance, a russet potato that seems very “close to nature.” While it has a good amount of fiber at 7 grams per serving, it’s off the charts with a high glycemic index of 111.

But it’s also important to understand that when they say “good” or “bad” carbohydrates, it’s in terms of where it falls on the glycemic index, not necessarily in terms of the food itself. So it’s not that a natural food like a russet potato or watermelon, which scores a relatively high 72, are bad foods because they’re not. They’re whole foods filled with good for you nutrients. They just score high on the glycemic index. Regardless, you can see why having an easily accessible list like the Harvard list is handy.

Glycemic Index: Who Came Up with This?

Back in 1981, David Jenkins, a professor of nutrition at the University of Toronto, invented the glycemic index to help those with diabetes. He determined how to test foods and assign a number to these foods to categorize them as blood sugar stabilizers or those that can cause havoc on your blood sugar. After giving his subjects the most common carbohydrates, he recorded their blood sugar levels at specific timeframes. Some of his findings were very interesting. For example, whole wheat bread has a higher glycemic index than ice cream. Didn’t see that coming did ya?

Low Glycemic Index Diet: What Is It and Does It Work?

The Low Glycemic Index Diet is what it sounds like: a diet plan that uses the glycemic index as the primary guide for meal planning. Eating foods that have a low glycemic index will help stabilize your blood sugar and insulin levels, a key to your long-term health. So the purpose of the Low Glycemic Index Diet is to eat carbohydrate containing foods that are less likely to cause a large jump in blood sugar levels. Pretty simple: eat more foods in the low-glycemic index category and fewer foods in the high-glycemic index category.

People follow the Low Glycemic Index Diet for various reasons. Some believe it will help them lose weight. Others need help planning and eating healthier meals. While others need help maintaining blood sugar levels.

However, the evidence is mixed on whether the Low Glycemic Index Diet actually works. Most individuals will see the same health benefits by eating a healthy diet, achieving and maintaining a healthy weight, and getting regular exercise. It’s important to talk with your doctor before starting a low glycemic index diet, especially if you have diabetes.

RECOMMENDED READING: 5 Steps to Prevent Diabetes

Low Glycemic Index Diet: Sugar Busters!

Sugar Busters! is one of the most popular low glycemic diets. It’s based on the simple notion that without insulin, your body can not store fat. So in theory, controlling insulin will not only prevent weight gain, but actually promote weight loss by allowing your body to burn stored fat instead of glucose for energy. So Sugar Busters! bases much of its meal planning on the glycemic index of foods. The premise is to lose weight on a diet that is high in dietary fiber, with an appropriate mix of fruits, vegetables, proteins, whole grains, and of course, eating foods with a low glycemic index.

While no food groups are off limits in Sugar Busters!, foods such as white rice, white potatoes, white flour, white bread, corn, beets, soda, candy, baked goods, and refined sugars are forbidden on the diet. 30-40% of calories are to be from carbohydrates. 30% of calories are to be from fat. And 30% of calories are to be from protein, namely lean meats such as white meat chicken, turkey, fish, lean cuts of beef and pork. But nuts and seeds are also encouraged. Low fat or fat free diary is allowed, but you have to be careful because often times, sugars are added to such foods to help their taste since there’s less fat to add flavor. The participant is to eat 3-6 meals per day, with 3 grams of sugar or less per serving, and never eat after 8 pm. Since artificial sweeteners have a glycemic index of 0 and have no effect on blood sugar levels, Sugar Busters! allows for using things like Sweet ‘N Low, Splenda, and NutraSweet.

Given the parameters of Sugar Busters! it’s no wonder so many people have had success on the plan.

Low Glycemic Index Diets… A Dietitian’s Opinion

As a dietitian, I like that that the Glycemic Index is well defined with repeatable results. It’s a specific science that gives you a tried and true number to kind of “grade” your carbohydrates. That means ten years from now we won’t see a change in glycemic index value. It will always be the same.

But on the other hand, it confuses me too. For instance, why is wheat bread higher on the glycemic index than ice cream? It has to do with the amount of fat found in ice cream, but that doesn’t mean you should eat ice cream over whole wheat bread solely because of glycemic index.

Overall, I’m a fan of Sugar Busters! I like how it limits carbohydrates and focuses on lean meats. I also like how they emphasize having a colorful diet. In general, a diet that is colorful with a wide variety of fruits and vegetables will ensure that you are receiving appropriate amounts of important nutrients. And I also like that it emphasizes 30% of calories are to come from protein. That will help your body build lean muscle mass.

That being said, I do find it a bit restrictive. Some foods are totally off limits. The restrictions, such as no refined sugar, potatoes, white bread, etc., would make it difficult for me (and probably others) to follow. I am not crazy about any diet that sets you up for failure by making a particular food completely forbidden.

Even though I am a fan of Sugar Busters! and other low glycemic index diets such as South Beach, you know what I’m a bigger fan of? Moderation, moderation, moderation! God gave us dominion over the earth to enjoy. Eat and enjoy it! Have some fruit or a potato guilt free. Just be sure to listen to your body. Stop when you are satisfied. Get regular exercise. And be honest with yourself and with Him as you give thanks and seek to be a wise steward of the body He has entrusted to you.