Glycemic load vs. glycemic index: Which is better for glucose control?

The glycemic load (GL) and glycemic index (GI) are two different tools that give you insight into how carb-rich foods affect your glucose levels, also known as your blood sugar levels. GI and GL can help you make informed food choices towards steady, healthier glucose levels. And healthier blood glucose levels translate to more energy, improved mood, and less hunger, among other benefits. ¹ 

Glycemic load vs. glycemic index: How they’re measured  

The glycemic index ranks carb-containing foods by their ability to raise glucose on a scale of 1-100, with 100 indicating that the food spikes your blood sugar the most. Glycemic index values are broken down into three ranges based on their numeric scores: 

• High GI: 70 to 100 
• Medium GI: 56 to 69 
• Low GI: 55 and below 

The GI is calculated by measuring how quickly certain carb-containing foods spike glucose levels in people without diabetes. Each food is given a numeric score based on the time it takes for blood sugar to rise after eating a portion of the food that contains 50 grams of carbs. The lower the GI of a food, the more steadily the food releases glucose into your bloodstream, providing sustained energy. The numeric GI ranking of each food is compared with glucose (pure sugar), the most quick-digesting carb that scores 100 on the GI scale. ² 

Low-GI foods produce less fluctuation in blood glucose and insulin levels than high GI foods because their digestion and absorption is slowed by their fiber content, or because the sugars present (e.g. fructose, lactose) are inherently less glycemic. In addition to your glucose staying steady, research shows health benefits when low-GI foods replace high-GI foods in a balanced diet. ³

The glycemic load, on the other hand, can give you a more practical measure of how a certain food impacts your glucose levels. The GL goes beyond the standardized measure of a 50-gram carb serving of a single food. It takes into account both how fast blood glucose is raised as well as how much glucose (aka carbohydrates) the food actually contains. ⁴ For example, watermelon has a high GI of 72, however a 1-cup serving of watermelon only has ~11 grams of carbohydrates, giving it a lower GL.  

To calculate the glycemic load, you’ll take the GI of a food (the numeric score), multiply it by the amount of carbs (in grams) in a portion of food, and then divide that number by 100. ⁵ 

Here’s an example of how that works out: If whole-wheat bread has a GI of 45 and one slice has 20 grams of carbs, you’ll multiply 45 by 20 and then divide that number by 100. The result is 9. That means whole-wheat bread has a low glycemic load. 

• Low glycemic load: 0 to 10 
• Medium glycemic load: 11 to 19 
• High glycemic load: 20 and above 

Glycemic load vs. glycemic index: Which is better?   

The GL improves on the glycemic index since it considers both the quality (GI) of the carbohydrate as well as that quantity of the carbohydrates in a serving of the food. This can give you more insight into how much your glucose may increase whereas the GI just tells you how fast a food raises your glucose without taking into account how much of that food you will actually consume. 

And the amount of glucose you eat coupled with how fast it creates a glucose spike (aka the GL) is a more accurate picture of how a food affects your overall glucose levels than merely how quickly a food’s sugars are absorbed (aka the GI).  

Let’s look at the whole-wheat bread example again. While whole-wheat bread has both a low GI and low GL, not all foods follow the same trajectory. Take boiled white spaghetti: It is low-glycemic, scoring a 46 on the GI scale. However, one serving of cooked spaghetti contains 43 grams of carbohydrates, giving it a glycemic load of 20, which is considered high. And the longer you boil it, the higher its glycemic index rises because cooking it for longer reduces the amount of digesting your body must do, which means your glucose will rise faster after eating it. ⁶   

Refined-grain products like white pasta will often have a high GL, but you can easily swap them for higher-fiber counterparts to lower the GL and help lessen that glucose spike. For reference, whole-wheat spaghetti, which is made of whole-grain flour rather than refined white flour, has a low GI ⁴⁰ and low GL ¹⁰ while regular spaghetti has a low GI ⁵⁵ but medium GL ¹³; so whole-wheat spaghetti would be a smart swap. Pairing your whole-grain pasta with a source of protein and fat (such as chicken cooked in a bit of olive oil) can further help lower how fast and how high your glucose rises. ⁶  

What are the downsides?  

The glycemic index is skewed because it doesn't take into account the realistic serving size of a food and exactly how many carbohydrates it contains. This can be a bit misleading because while a certain food can raise your blood sugar quickly, if a typical serving of that food does not contain a high amount of carbohydrates, then it may not spike your glucose into an unhealthy range. ⁴ 

While the glycemic load is a more useful measure of how carb foods affect your glucose, this tool isn’t perfect, either. The GL still takes into account how one specific food affects your glucose, so if you’re not eating that food on its own, it’ll be more difficult to figure out your meal or snack’s glycemic load. For example, pairing a piece of bread with cheese will produce a lower GL than eating a plain piece of bread. And combining pasta with chicken and Parmesan will also put less of a burden on your blood sugar than eating pasta alone. That’s because foods with protein and fats (like chicken and cheese) can help slow down the digestion of the carbs you’re eating along with them, which means more steady glucose levels and more sustained energy. ⁶ 

A better way to measure how foods and meals affect your glucose levels is by using a continuous glucose monitor (CGM) like Lingo. A CGM can monitor your glucose throughout the day and give you insights into how what you eat and drink influences your glucose. Using this info, you can tailor your diet plan for steadier glucose levels and improve your overall well-being.  

A final note from Lingo  

Both the glycemic load and glycemic index paint a picture of how food affects your blood glucose levels, but the glycemic load is a more practical measure. Unlike the GI, the GL takes into account how many carbohydrates a serving size of a specific food contains. The GI only tells you how fast a carb-containing food raises your glucose levels, without factoring in what a typical serving size of that food is.  

What both measures don’t tell you is how much these foods, when paired with sources of fat or protein (which don’t spike glucose), affect your glucose levels. And that’s where a CGM like Lingo can help. 

To create meals with a lower glycemic load, replace high-GI foods with lower-GI foods and pair your carbs with a source of protein and/or fat. If you're eating a high-GI food (which is OK in moderation), watch portion sizes and eat it after a mixed-macro meal that has protein, veggies, and healthy fat for healthier glucose levels.  

^ALB-02404