What It Is and How to Use It
The glycemic index is a tool that’s often used to promote better blood sugar management.
Several factors influence the glycemic index of a food, including its nutrient composition, cooking method, ripeness, and the amount of processing it has undergone.
The glycemic index can not only help increase your awareness of what you’re putting on your plate but also enhance weight loss, decrease your blood sugar levels, and reduce your cholesterol.
This article takes a closer look at the glycemic index, including what it is, how it can affect your health, and how to use it.
The glycemic index (GI) is a value used to measure how much specific foods increase blood sugar levels.
Foods are classified as low, medium, or high glycemic foods and ranked on a scale of 0–100.
The lower the GI of a specific food, the less it may affect your blood sugar levels (1).
Here are the three GI ratings:
- Low: 55 or less
- Medium: 56–69
- High: 70 or above
Foods high in refined carbs and sugar are digested more quickly and often have a high GI, while foods high in protein, fat, or fiber typically have a low GI. Foods that contain no carbs are not assigned a GI and include meat, fish, poultry, nuts, seeds, herbs, spices, and oils.
Other factors that affect the GI of a food include the ripeness, cooking method, type of sugar it contains, and amount of processing it has undergone (2).
Keep in mind that the glycemic index is different from the glycemic load (GL).
Unlike the GI, which doesn’t take into account the amount of food eaten, the GL factors in the number of carbs in a serving of a food to determine how it may affect blood sugar levels (1).
For this reason, it’s important to take both the glycemic index and glycemic load into consideration when selecting foods to help support healthy blood sugar levels (1).
The glycemic index is used to measure how much a specific food increases your blood sugar levels. The higher the GI, the greater the effect on blood sugar levels.
The low glycemic diet involves swapping out foods with a high GI for those with a lower GI.
Following a low glycemic diet may offer several health benefits, including:
- Improved blood sugar regulation. Many studies have found that following a low GI diet may reduce blood sugar levels and improve blood sugar management in people with type 2 diabetes (3, 4).
- Increased weight loss. Some research shows that following a low GI diet may increase short-term weight loss. More studies are needed to determine how it affects long-term weight management (5, 6, 7).
- Reduced cholesterol levels. Following a low GI diet may help lower levels of both total and LDL (bad) cholesterol, both of which are risk factors for heart disease (8, 9).
How to follow
A healthy, low glycemic diet should comprise mostly low GI foods, such as:
- Fruits: apples, berries, oranges, lemons, limes, grapefruit
- Non-starchy vegetables: broccoli, cauliflower, carrots, spinach, tomatoes
- Whole grains: quinoa, couscous, barley, buckwheat, farro, oats
- Legumes: lentils, black beans, chickpeas, kidney beans
Foods without a GI value or with a very low GI can also be enjoyed as part of a balanced low glycemic diet. They include:
- Meat: beef, bison, lamb, pork
- Seafood: tuna, salmon, shrimp, mackerel, anchovies, sardines
- Poultry: chicken, turkey, duck, goose
- Oils: olive oil, coconut oil, avocado oil, vegetable oil
- Nuts: almonds, macadamia nuts, walnuts, pistachios
- Seeds: chia seeds, sesame seeds, hemp seeds, flax seeds
- Herbs and spices: turmeric, black pepper, cumin, dill, basil, rosemary, cinnamon
Although no foods are strictly off-limits on the diet, foods with a high GI should be limited.
Foods with a high GI include:
- Bread: white bread, bagels, naan, pita bread
- Rice: white rice, jasmine rice, arborio rice
- Cereals: instant oats, breakfast cereals
- Pasta and noodles: lasagna, spaghetti, ravioli, macaroni, fettuccine
- Starchy vegetables: mashed potatoes, potatoes, french fries
- Baked goods: cake, doughnuts, cookies, croissants, muffins
- Snacks: chocolate, crackers, microwave popcorn, chips, pretzels
- Sugar-sweetened beverages: soda, fruit juice, sports drinks
Ideally, try to replace these foods with foods that have a lower GI whenever possible.
Following a low glycemic diet involves swapping out foods that have a high GI with low GI alternatives. A low glycemic diet may help manage blood sugar levels, reduce your cholesterol, and boost short-term weight loss.
Determining the GI of foods that you often eat can be useful if you’re following a low glycemic diet.
Here are the GI values for a few ingredients (10, 11):
- Apples: 36
- Strawberries: 41
- Dates: 42
- Oranges: 43
- Banana: 51
- Mango: 51
- Blueberries: 53
- Pineapple: 59
- Watermelon: 76
- Carrots (boiled): 39
- Plantains (boiled): 66
- Sweet potatoes (boiled): 63
- Pumpkin (boiled): 74
- Potatoes (boiled): 78
- Barley: 28
- Quinoa: 53
- Rolled oats: 55
- Couscous: 65
- Popcorn: 65
- Brown rice: 68
- White rice: 73
- Whole wheat bread: 74
- White bread: 75
- Soybeans: 16
- Kidney beans: 24
- Chickpeas: 28
- Lentils: 32
Dairy products and dairy alternatives
- Soymilk: 34
- Skim milk: 37
- Whole milk: 39
- Ice cream: 51
- Rice milk: 86
- Fructose: 15
- Coconut sugar: 54
- Maple syrup: 54
- Honey: 61
- Table sugar: 65
Knowing where your favorite foods fall on the glycemic index can make it much easier to follow a low glycemic diet.
For certain foods, the cooking method used can affect the glycemic index.
For example, fried foods tend to contain a high amount of fat, which can slow the absorption of sugar in the bloodstream and decrease the GI (12, 13).
Meanwhile, roasting and baking can break down resistant starch — a type of starch that resists digestion and is commonly found in foods like legumes, potatoes, and oats — thus increasing the GI (12, 14).
Conversely, boiling is thought to help retain more of the resistant starch and lead to a lower GI, compared with other cooking methods (12).
The longer you cook foods like pasta or rice, the greater the digestibility of their starch content, and thus the higher their GI. As such, it’s best to only cook these foods until they reach an al dente texture, meaning that they’re still firm when biting into them (15, 16).
In addition to the cooking method used, the degree of ripeness may also affect the GI of some fruits, including bananas. This is because the amount of resistant starch decreases during the ripening process, leading to a higher GI (17).
For example, bananas that are fully ripened have a GI of 51, whereas under-ripe bananas have a GI of just 30 (11).
The degree of ripeness, as well as the way that certain foods are cooked and prepared, can affect the GI of the final product.
The glycemic index, or GI, is a measure used to determine how much a food can affect your blood sugar levels.
Several factors affect the glycemic index of a food, including the nutrient composition, ripeness, cooking method, and amount of processing it has undergone.
Following a low glycemic diet may offer several health benefits, as it could help balance your blood sugar levels, lower your cholesterol, and increase short-term weight loss.