Emerging research shows that not all calories are processed in the same way. In particular, the quantity and quality of carbohydrates consumed affects insulin release, hunger, and fat storage. Glycemic index (GI) is an objective way of measuring this effect. This Integrative Health tool defines glycemic index and glycemic load and explains how they can be used. Resources for gathering more information are provided below.

What Is Glycemic Index?

The glycemic index of a food refers to the effect the food has on the body’s blood sugar levels. Blood sugar levels are raised after a person eats foods containing carbohydrates (sugars and starches). Various carbohydrate-containing foods affect blood sugar levels differently. This is a function of the type and quantity of carbohydrate, as well as the method of preparation and the presence of other substances in the food, such as soluble fiber, fat, and protein. For example, your body absorbs glucose from whole fruit differently from extracted fruit juice due to the fiber content.

The glycemic index compares the rise in blood sugar level after eating a particular food to a reference food, often glucose. Glucose has a GI of 100. The GI of fructose is 25 and sucrose, which is a blend of the previous two, has a GI of 65. Most natural sweeteners are a combination of these three carbohydrates. Figure 1 shows the difference between a low GI and a high GI food in terms of effects on blood glucose levels over time.