Introduction
The glycemic index (GI) is a numerical scale that measures how much a particular food increases blood sugar levels and ranks them from 0 to 100. So, the lower a food’s glycemic index is, the slower it will raise blood sugar levels after being eaten. Whole, minimally processed foods tend to have a lower glycemic index because they contain more fiber and fat. The glycemic index can be a great tool–not just for diabetics–to maintain stable blood sugar levels and prevent spikes.
Although the glycemic index is helpful, it definitely doesn’t show the whole picture. The GI tells how quickly certain foods will affect blood sugar, but not by how much. This is where the glycemic load comes in. The glycemic load tells how quickly a food causes glucose to enter the bloodstream, as well as how much glucose the food can deliver. To calculate a food’s glycemic load, you can multiply the GI by the amount of available carbohydrates, and then divide by 100. Available carbohydrates refers to the total carbohydrate content, minus fiber.
GL = (GI x amount of available carbohydrates in grams) / 100
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Low GL |
10 or less |
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Medium GL |
11-19 |
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High GL |
20+ |
It’s important to understand both the glycemic index and load because a food can be high on one scale, but not the other. An example of this is watermelon. Watermelon has a high glycemic index (72), but low glycemic load (5.6). This is because it contains natural sugars that can quickly enter the bloodstream, but a relatively low amount per serving because of its high water content.
Factors that Affect the Glycemic Index of Foods
Type of Carbohydrate
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Complex carbohydrates, like those in whole grains and vegetables, digest slower than simple carbohydrates and have a lower GI.
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Refined and heavily processed sweets contain higher amounts of sugars and simple carbs. These foods digest quickly and have much greater impacts on blood sugar. Eating these types of foods with the addition of fat, protein, and fiber can reduce the impact of GI and blood sugar.
Macronutrient Content
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Fat and protein slow down the digestion of foods and can lower the GI of a meal.
Food Processing
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Processing methods can break down the structure of carbs, making them easier to digest and more available for absorption. This causes them to hit the bloodstream quicker and have greater impacts on blood sugar levels. Some processing methods also strip food of fiber and nutrients, which also help slow digestion. Removing these things leads to a higher GI.
Cooking Methods
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Some cooking methods like boiling and steaming can lower GI because they preserve more resistant starch, which slows digestion. Baking, roasting, and pressure cooking often increases GI because carbohydrates are broken down and made more easily digestible.
Impacts of GI and GL on Health
Weight Management
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Insulin plays a big part in the storage and usage of energy (glucose). Stable insulin levels can promote fat burning because the body is less likely to store fat for energy.
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Low GL foods maintain satiety, helping to lower overall calorie intake.
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Reducing glucose spikes and subsequent crashes helps to reduce cravings and overeating.
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Stable blood glucose and insulin levels reduce the risk of type 2 diabetes, cardiovascular disease, and other chronic diseases.
Improved Energy Levels
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Avoiding blood sugar spikes and crashes will provide stable energy throughout the day.
Digestive Health
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Fiber-rich foods promote gut health and better digestion.
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A healthy gut microbiome supports digestion, strengthens the immune system, enhances nutrient absorption, and may even improve mood and cognitive function.
Food Examples: Glycemic Index and Load
High GI Foods
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Refined grains (white bread, white rice), sugary snacks and desserts, baked potatoes, breakfast cereals.
Low GI Foods
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Whole grains (quinoa, oats), sweet potatoes, beans, lentils, most fruits and vegetables.
Moderate to High GL Foods
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Tropical fruits, refined grains, rice cakes, sugary snacks and desserts.
Low GL Foods
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Carrots, apples, berries, whole grains, beans and lentils, nuts and seeds, most fruits and vegetables.
Incorporating GI and GL into Your Diet
Focus on Low to Moderate GL Foods
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Aim to include more whole grains, legumes, and non-starchy vegetables in your meals.
Combining Foods
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Combining foods with a higher GI with protein, fiber, and healthy fats can lower the overall GL of the meal. This can look like pairing carbs with protein (chicken with rice and veggies), including healthy fats (avocado and egg with toast, adding nut butter to fruit), and adding fiber to meals (adding chia seeds and berries to oatmeal).
Be Mindful of Portion Sizes
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Even foods with a low glycemic index can have a high glycemic load if consumed in large quantities. Portion control can help to manage glycemic load.