If you have diabetes or prediabetes, you may have come across terms like “glycemic index” (GI) and “glycemic load” (GL) when putting together a blood sugar-friendly diet, but understanding what they are and distinguishing between the two is important. Although they sound the same, there are key differences between them.
If you’re focused on better blood sugar control, glycemic load is a better choice. Keep reading to learn why.
Understanding Glycemic Index
The glycemic index is a ranking system that measures how quickly carbohydrate-containing foods raise blood sugar levels. Foods are scored from 0 to 100, with pure glucose, at 100, representing the fastest blood sugar spike.
Foods with a high GI (above 70) are quickly digested and can cause rapid rises in blood sugar. These include simple carbs like white bread, white rice, instant oats and sugary snacks. Conversely, low-GI foods (below 55), including whole foods like lentils, apples and steel-cut oats, release glucose gradually, resulting in a slower, more sustained rise in blood sugar.
That said, there are limits to the application of GI in one’s regular diet. “Glycemic index uses a standardized portion size—usually 50 grams of carbohydrate from a particular food—rather than the typical serving size people would consume,” explains Erin Palinski-Wade, RD, CDCESa registered dietitian and author of the 2-Day Diabetes Diet. “This means GI doesn’t always reflect real-world consumption. For instance, watermelon has a high GI of 80, but a standard serving contains relatively few carbs, so its impact on blood sugar is minimal,” she explains.
Glycemic Index Categories
Here is a breakdown of the glycemic index categories and some examples.
- Low GI (55 or less): Minimally processed foods like legumes, nonstarchy vegetables and whole grains.
- Medium GI (56–69): Foods like bananas, sweet potatoes and popcorn.
- High GI (70 or more): White bread, rice cakes and sugary cereals.
Understanding Glycemic Load
While GI is useful, it doesn’t account for portion sizes. That’s where glycemic load comes in. GL considers both the GI of a food and the actual amount of carbohydrates in a typical serving. “This provides a more accurate assessment of how a food affects blood sugar,” says Palinski-Wade.
Glycemic Load Categories
Glycemic load categories are as follows:
- Low GL (10 or less): Foods like carrots, peanuts and broccoli.
- Medium GL (11–19): Foods like bananas, sweet potatoes and popcorn.
- High GL (20 or more): Foods like white rice, white bread and sugary drinks.
Glycemic Index vs. Glycemic Load: Key Differences
While both GI and GL can help you predict how foods impact your blood sugar, they have distinct differences. GI ranks foods based solely on how quickly they raise blood sugar depending on a 50-gram serving size. GL, however, gives a more nuanced picture by considering food quality and typical portion size.
Palinski-Wade says, “GI can be misleading if you’re only looking at the numbers. A food with a high GI may have a low GL if eaten in small portions, meaning it will have little impact on blood sugar.”
GL is more practical for real-world eating habits. Take carrots, for example. They have a high glycemic index (85 out of 100), but their glycemic load for a typical serving size is low (4.25), meaning they’re unlikely to cause a significant blood sugar spike. If you were to look at glycemic index alone, you might skip carrots entirely out of worry about their blood sugar effects.
Which One Should You Use?
Glycemic load is more practical when it comes to managing blood sugar levels. “GL more accurately reflects how a food will impact blood sugar levels, because it considers both the food and the portion size consumed,” explains Palinski-Wade.
However, neither GI nor GL are perfect, Palinski-Wade cautions. “What you eat alongside carbohydrate-containing foods—such as protein, fat or fiber—as well as timing, activity level and stress, can all influence blood sugar responses.”
Palinski-Wade recommends tracking your meals and monitoring blood sugar levels to understand better how your food choices impact your blood sugar. “I often advise my clients to use apps like MyFitnessPal to record their food intake and sync it with continuous glucose monitors (CGMs),” she says. “This helps them see real-time correlations between their meals and blood sugar levels, making it easier to adjust their diet for better glucose control.”
The Bottom Line
Glycemic index and glycemic load are valuable tools for making informed food choices, especially when managing blood sugar levels. GI lets you know how quickly a food may raise blood sugar, while GL gives a more comprehensive understanding by factoring in portion sizes and food quality.
For most people, focusing on glycemic load is more practical for real-world eating and blood sugar management. However, the best approach is to regularly monitor your blood sugar levels to understand how specific foods impact you. Speak with your health care provider or a registered dietitian if you have any questions about creating a diet that helps you best manage your blood sugar levels.
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