How to Figure Glycemic Index

To get a better idea of what you're eating, you should know the mix of protein, fats, and carbohydrates that make up your meals. The glycemic index helps consumers do that by measuring the amount of carbs in various foods. This calculation can be helpful for people on a strict diet due to health reasons, or simply for those who are watching their waistlines and aim to reduce carbohydrate intake. Read on to learn how to factor this index for an entire serving of food.

Things You'll Need

• Calculator
• Nutritional labels and guide

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Instructions

• 1

  Add up all the grams of carbohydrates in a given serving of food, like a blueberry muffin and a banana. Reference the food's nutrition labels, or use a nutritional guide that lists the type and amount of carbs in a variety of common foods.

• 2

  Figure out which foods you are about to eat, include carbohydrates, and then find their glycemic index values in a reference guide; many diabetes magazines have a glycemic index list. For the blueberry muffin, this value is listed at 59.

• 3

  Next, determine how many grams of each carb you will eat.

• 4

  Divide the grams of each different carbohydrate group by all the carbohydrate grams in the meal. If you are eating a muffin, for example, that might be about 30 grams of carbohydrates. Now divide 30 by the total carb load of the meal or snack (30g of carbs for the muffin plus about 27 for the banana) to yield the percentage contribution of the carbohydrate.

• 5

  Multiply the carbohydrate's percentage contribution (0.52%) by the glycemic index of that particular type of carbohydrate. For the blueberry muffin, this would mean multiplying 0.52 by 59. The final calculation is then a glycemic index of approximately 30.7mg for the blueberry muffin.

• 6

  Complete this same calculation for all of the different carbohydrates included in the meal, then add the results to yield the total glycemic index of the meal, if desired.