Glycemic Index, Glycemic Load, and How It Impacts Your Glucose

October 4, 2021
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Key Takeaways

  • The glycemic index (GI) is a number assigned to a food based on how quickly it raises blood sugar.
  • The glycemic load (GL) equals the glycemic index of a food multiplied by the number of carbs in a serving of that food divided by 100.
  • The GI and GL of foods can provide a guide for which foods may cause your blood glucose to rise.
  • Do all carbs, or just those with high GI/GL, spike your blood sugar? The answer depends on the context in which the carbs were consumed.

Reviewed by Signos Nutritionist Jodi Geigle

As scrutiny of carbohydrates continues in diet culture, you may be vaguely familiar with terms associated with blood sugar management such as glycemic load and glycemic index. 

What do these terms mean and why should you care about them if you’re trying to lose weight, eat well, and be the healthiest version of yourself?

The Glycemic Index of Foods

The glycemic index (GI) assigns a number to a food based on how quickly it raises blood sugar (aka blood glucose). The glycemic index ranks carbohydrates on a scale of 0 to 100, determined by how quickly and how much these foods raise blood glucose after eating.

How the glycemic index scale works:

  • 50 grams (½ cup) of glucose (simple sugar) has a GI score of 100
  • All other foods are assigned a GI score compared to the GI score of 50g of glucose
  • A food that raises blood sugar by 50% as much as glucose has a GI score of 50.

Foods with a high glycemic index digest rapidly and can cause dramatic fluctuations in blood glucose, or glucose spikes.

The glycemic index scale:

  • High glycemic index foods = GI score of 70–100
  • Medium glycemic index foods = GI score of 50–69
  • Low glycemic index foods = GI score of 20-49

When you eat a food with a high-glycemic score by itself (without eating any fat, fiber, or protein along with it), you can see your glucose spike in the Signos app. The bigger the area under the curve of the glucose spike, the faster that food raises your blood sugar.

The glycemic index of foods can be helpful in discerning simple carbs (one or two sugars linked together; digests quickly and releases sugar into the blood rapidly) from complex carbs (three or more sugars linked together; contains fiber, vitamins, and minerals that make them slower to release sugar into the bloodstream).

Glycemic Index of Common Foods

FoodGlycemic IndexValueRice milk86HighCornflakes81HighPotatoes, boiled78HighWhite bread75HighWatermelon76HighWhole wheat bread74HighWhite rice, boiled73HighBrown rice, boiled68MediumOats, quick-cooking65MediumPopcorn65MediumSweet potato, boiled63MediumSweet corn52MediumBanana, ripe52MediumMango51MediumIce Cream51MediumSpaghetti, white49LowOrange43LowChocolate40LowApple36LowSource: American Diabetes Association1

Certain variables can affect the GI score of foods, including:

  • Ripeness: Riper fruit has a higher GI. Does the skin of your banana contain some green, some black spots, or many black spots? Many black spots on the peel indicate ripeness. A slightly under-ripe banana2 has a GI of 42, a ripe banana has a GI of 50, and an overripe banana has a GI of 52.
  • Processing: Minimally processed whole grains tend to have a lower GI score than milled and refined grains. 
  • Fiber content: High-fiber foods contain indigestible carbs, which slow down the rate of digestion and cause a less dramatic rise and fall of glucose3.
  • Sugar type: Fructose4 (fruit sugar) has a lower GI score than lactose5 (milk sugar).
  • Preparation method: Temperature, duration of cooking, cooling, and reheating can impact the GI score of food. Two-thirds of a cup (150g) of boiled millet6 has a GI score of 71, whereas the same amount of millet that was soaked for 12 hours, stored moist for 24 hours, then steamed for one hour has a GI score of 68.

The Glycemic index provides elemental information that can be contextualized by the glycemic load of food. The glycemic load provides a better answer to the question: What can happen to my blood glucose if I eat high-glycemic, medium-glycemic, or low-glycemic food?

The Glycemic Load of Foods

The glycemic load gives a more specific overview of how much glucose a serving of that food contains and how quickly it will enter your bloodstream. How do we arrive at enhanced specificity? Through math, of course.

For example, the glycemic index of ¾ cup (150 grams) of fresh-cooked Calrose medium-grain white rice has a GI of 83, a glycemic load of 36, and 43 grams of carbs.

The glycemic load is calculated by the amount of carbohydrates in a portion of food and its glycemic index.

The mathematical breakdown:

  • Glycemic index multiplied by carbs in grams divided by 100 = glycemic load

Here’s how to calculate the glycemic load of ¾ cup of Calrose medium-grain white rice:

  • 83 (glycemic index) x 43 grams / 100 = 36

So does this mean that ¾ cup of just-cooked Calrose white rice has a high-glycemic load? Here’s the glycemic load scale for 1 serving of food:

  • High glycemic load: 20 and higher
  • Medium glycemic load: 11-19
  • Low glycemic load: 10 or less

Yes, ¾ cup of Calrose white rice has a high-glycemic load.

What does this look like in real life? Let’s take a look at what happens to the glucose of two people—a man, Bill, and a woman, Hannah—who ate one cup (200 grams) of cooked white rice.

On the following day, both Signos users ate the same amount of white rice without any other foods, but they ate it after it had cooled overnight in the refrigerator (Hannah re-heated hers in the microwave).

The cooling of the rice caused the development of resistant starch, which helped slow down the glucose response for Hannah but did not do the same for Bill. Interestingly, Bill’s glucose spike increased after eating the cooled rice on the second day.

This shows that people’s response to high-glycemic foods—and any food, for that matter—can vary. The glycemic index and glycemic load can provide an initial guide for which foods may raise your blood sugar, but the context in which you eat potentially glucose-spiking foods matters more.

So, Which Is Better: Glycemic Index or Glycemic Load?

The short answer: Both!

The longer answer: You can’t calculate the glycemic load of food without knowing its glycemic index. While the GL of food can better predict how your glucose will respond to eating a serving of that food, you can assume that foods with a high GI score will likely have a high GL score as well. 

A food with a high GI and GL score will most likely cause a glucose spike, but there are strategies you can implement to lower, mitigate, and even thwart a glucose spike and still enjoy that high-GI/GL food occasionally.

4 Strategies to Consider When Enjoying Carbs

Do all carbs, or just those with high GI/GL, spike your blood sugar? The answer depends on the context in which the carbs were consumed. Some things to consider:

  • Did you eat high-GI food by itself? This will likely raise your blood glucose rapidly.
  • Did you pair a medium-GI food with fat, protein, or fiber? Say you added sweet potato cubes to a spinach salad with avocado and chicken breast. This probably won’t spike your glucose unless you coat the salad in a dressing with lots of added sugar and eat two large slices of toasted baguette with it as well.
  • How much of the food did you eat? Large portions of even low-GI/GL foods could spike your glucose, although probably not super high.
  • Did you just finish a moderate-intensity workout and then chug a glass of fruit juice? Whether you spike or not may depend on how long you exercised (did you deplete your glycogen stores?), what else you ate or did that day, and which foods you choose to eat with a high-GI food. If it’s chocolate cake after a 20-minute bike ride, you might spike. If it’s a protein-rich smoothie made with fruits and vegetables and some fat after a 30-minute weight training circuit, you likely won’t spike.

All that said, if you often eat isolated simple carbs—such as candy, milk, or grapes—that release sugar into the bloodstream rapidly, you should plan to use up that energy. Go for a run, hike, cycle, swim, lift weights, complete a full-body circuit workout, chop firewood, rake leaves, heave your children over your head… you get the idea. 

Frequent consumption of simple carbs causes rapid rises in glucose and insulin. Without a plan in place to use all of that extra energy, your body stores it. Piling on more high-glycemic food consumption without burning the excess sugar causes a glucose storage cycle that, over time, can cause weight gain7 (especially abdominal obesity in women8, type 2 diabetes9, cardiovascular disease10, and other health issues11.

Foods That Are Unlikely to Spike Your Glucose

The following foods are unlikely to cause high glucose spikes, but keep in mind that everyone’s response can be different. Test these foods out for yourself, play around with food combinations, and have some fun experimenting.

Vegetables

Starchy vegetables, such as potatoes, peas, pumpkin, and plantains, are more likely to spike your glucose compared to non-starchy veggies. Enjoy starchy veggies in moderation or, better yet, in smaller amounts and paired with other non-starchy vegetables, a protein source, and a little healthy fat like olive oil or almonds.

  • Artichokes
  • Arugula
  • Asparagus
  • Bok choy 
  • Broccoli
  • Broccoli raab 
  • Broccolini 
  • Brussels sprouts 
  • Cabbage 
  • Carrots
  • Cauliflower
  • Celery 
  • Celeriac 
  • Chard 
  • Collards 
  • Eggplant 
  • Endive 
  • Fennel 
  • Garlic 
  • Green beans 
  • Hearts of palm 
  • Jicama 
  • Kale
  • Kohlrabi 
  • Leeks 
  • Lettuces 
  • Mushrooms 
  • Mustard greens 
  • Onions 
  • Parsnips 
  • Peppers 
  • Radishes 
  • Snap peas 
  • Snow peas 
  • Spinach 
  • Sprouts 
  • Summer squash 
  • Turnip 
  • Zucchini

Fruits

Low-glycemic and even some medium-glycemic fruits may not spike your blood sugar, but everyone’s response to these fruits can differ. The context in which you eat fruit can impact your glucose response as well. For example, eating medium-glycemic fruit shortly after a workout may not raise your glucose as high as it may have if you ate it before exercise.

  • Apples
  • Apricots
  • Avocado
  • Blackberries
  • Blueberries
  • Cherries (sour, raw)
  • Coconut (unsweetened)
  • Cranberries (unsweetened)
  • Cucumbers
  • Durian
  • Grapefruit
  • Green bananas
  • Kiwi
  • Lemons
  • Limes
  • Olives
  • Pears
  • Plums
  • Strawberries
  • Tomatillos 
  • Tomatoes

Meat, Fish, Seafood

  • Beef
  • Bison
  • Chicken
  • Fish
  • Lamb
  • Pork
  • Shellfish
  • Turkey
  • Venison

Beans and Legumes

  • Blackeyed peas 
  • Black beans 
  • Chickpeas 
  • Navy beans 
  • Kidney beans 
  • Lentils 
  • Soybeans*

 *Soy can cause some people to spike; experiment with it to see how you react.

Nuts and Seeds

  • Almonds
  • Brazil nuts
  • Cashews 
  • Chia seeds
  • Flaxseeds
  • Hazelnuts
  • Hemp seeds/hearts 
  • Macadamia nuts
  • Nut butters (unsweetened)
  • Peanuts 
  • Pine nuts
  • Pistachios
  • Pumpkin seeds
  • Sunflower seeds
  • Walnuts

Eggs, Dairy, Non-Dairy Alternatives

If you enjoy dairy, can digest it well, and choose to eat it, we recommend organic, full-fat varieties. Lactose, the sugar in milk, can cause some people to spike. Avoid yogurt or kefir with added sugars. If you prefer non-dairy milk alternatives, steer clear of sweetened versions and high-glycemic varieties like rice and oat milks.

  • Butter
  • Cheese
  • Cottage cheese
  • Eggs
  • Ghee
  • Kefir (unsweetened)
  • Milk 
  • Nut and/or seed milks (unsweetened)
  • Non-dairy yogurt (unsweetened)
  • Sour cream
  • Yogurt (unsweetened)

For Advanced Signos Users

Experiment time! Select one of your favorite foods with a high glycemic load (remember that this is a portion of food with a high glycemic index). When your glucose is stable, eat a portion of that food and take a screenshot of your glucose response. The next day, eat the same amount of that food but combine it with a food with a medium or low GL as well as some protein or fat. Take a screenshot of your glucose response on Day 2, then compare the glucose graphs. What do you notice?

References

  1. https://care.diabetesjournals.org/content/31/12/2281.figures-only
  2. https://glycemicindex.com/gi-search/?food_name=banana
  3. https://www.ahajournals.org/doi/abs/10.1161/circ.131.suppl_1.20
  4. https://glycemicindex.com/gi-search/?food_name=fructose
  5. https://glycemicindex.com/gi-search/?food_name=lactose
  6. https://glycemicindex.com/gi-search/?food_name=millet
  7. https://pubmed.ncbi.nlm.nih.gov/17344493/
  8. https://pubmed.ncbi.nlm.nih.gov/30660436/
  9. https://pubmed.ncbi.nlm.nih.gov/17760498/
  10. https://pubmed.ncbi.nlm.nih.gov/17601539/
  11. https://pubmed.ncbi.nlm.nih.gov/14759990/
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