The glycemic index is a measurement of how a particular food that contains carbohydrates will impact your blood sugar after you eat it.
“A number between 0 and 100 assigned to food represents the relative rise in blood glucose levels two hours after consuming that specific food,” explains Vanessa Rissetto, RD, who runs a private nutrition practice in New York City. Since most fruits are sweet — and they all contain carbs — knowing which fruits are low-glycemic is helpful for anyone following a low-carb diet for weight loss.
The American Diabetes Association considers foods with a glycemic index of 55 or less to be “low glycemic index foods.” Pure glucose (sugar) ranks 100, which serves as the comparison for other foods.
“The glycemic index of food is not always related to the sweetness,” says Brocha Soloff, BS, RD, CDN, founder of iHeart Health. “It’s more related to the starch content, though higher-sugar mango and pineapple have a higher glycemic index than strawberries, for example.”
Carb counts vs. glycemic load
A food’s carbohydrate count is different from its glycemic index ranking and its glycemic load. The glycemic index is a ranking of that food’s carbs (and the impact on your blood sugar) using that scale of 0 to 100; its glycemic load is a measure of the food’s glycemic response, based on serving size. (Glycemic load = glycemic index x grams of carbs consumed / 100)
And while the glycemic index of foods can’t change, you can alter the effect they have on your blood sugar by combining higher-glycemic fruits and other foods with fat, fiber, and/or protein, says Soloff. One simple example would be to eat a banana (glycemic index: 51) with a spoonful of peanut butter (glycemic index: 14).
“The fat in the peanut butter will slow down the digestion of the banana and its entry into your bloodstream,” she says.