Why Glycemic Load (GL) is a Better Metric than Glycemic Index (GI)

October 26, 2025 •

3 min read

According to the Centers for Disease Control and Prevention, over 38 million Americans have diabetes, a condition highly influenced by blood sugar management. For those seeking to control blood glucose, the Glycemic Load (GL) is a far more practical and effective metric than the Glycemic Index (GI). This distinction is crucial for making informed dietary choices that lead to more stable energy levels and better long-term health outcomes.

Quick Summary

This guide explains why Glycemic Load (GL) surpasses Glycemic Index (GI) for blood sugar management by accounting for real-world portion sizes and total carbohydrate intake, not just speed of absorption.

Key Points

Portion Size Matters: GL is superior because it considers realistic serving sizes, whereas GI is based on a fixed 50g carbohydrate portion.
Holistic Impact: GL measures a food's total impact on blood sugar, combining both carbohydrate quality (GI) and quantity, for a more accurate picture.
Prevents Misleading Judgments: The GL framework corrects for foods like watermelon, which have a high GI but a low GL due to low carbohydrate density.
Better for Health Management: Following a low-GL diet can lead to more stable blood sugar, sustained energy, better weight control, and a reduced risk of chronic diseases.
Strategic Combinations: The overall GL of a meal can be lowered by combining carbs with protein, healthy fats, and fiber, which is not accounted for by GI alone.

Understanding the Glycemic Index (GI)

The Glycemic Index (GI), introduced in 1981, ranks carbohydrate-containing foods based on how quickly they elevate blood glucose levels. A food's GI score is determined by comparing the blood sugar response after consuming a portion with 50 grams of carbohydrates to the response from a reference food like glucose (GI of 100).

High-GI foods (70 or more) cause rapid blood sugar spikes due to quick digestion, while low-GI foods (55 or less) result in slower, more gradual increases. A key limitation of the GI, however, is its reliance on a fixed 50-gram carbohydrate portion, which may not reflect typical serving sizes. For example, watermelon has a high GI of 72, but a standard serving has only about 11 grams of carbohydrates, resulting in a minimal impact on blood sugar despite its high GI score.

The Superiority of Glycemic Load (GL)

The Glycemic Load (GL) was developed to provide a more practical measure by accounting for both carbohydrate quality (GI) and quantity (serving size). This offers a more accurate prediction of a food's actual impact on blood sugar.

Calculating Glycemic Load

GL is calculated using the formula: GL = (GI × grams of carbohydrates per serving) / 100.

Using the watermelon example (GI of 72, 11g carbs per serving), the GL is (72 × 11) / 100 = 7.92. This low GL score (typically 10 or less) accurately indicates that a serving of watermelon will not cause a significant blood sugar increase.

Comparison of Glycemic Index (GI) vs. Glycemic Load (GL)


Feature	Glycemic Index (GI)	Glycemic Load (GL)
Measurement	Rate of blood sugar increase.	Total blood sugar impact per serving.
Portion Size	Fixed 50g carb portion.	Realistic serving sizes considered.
Practicality	Less practical for daily diet.	More practical for daily diet.
Accuracy	Can be misleading due to fixed portion.	More accurate; considers quality and quantity.
Best for	General carb type comparison.	Precise blood sugar management.

Benefits of Focusing on a Low-GL Diet

A low-GL diet offers several health benefits, particularly for managing blood sugar and weight:

Stable Blood Sugar: Prevents rapid spikes and crashes.
Sustained Energy: Reduces energy slumps.
Improved Weight Management: Promotes fullness and can aid in weight loss.
Reduced Risk of Chronic Disease: Helps lower the risk of type 2 diabetes and heart disease.

How to Build a Low-GL Diet

Implementing a low-GL diet involves smart food choices and combinations.

Swap High-GL for Low-GL Alternatives:

Choose brown rice or quinoa instead of white rice.
Opt for whole-grain bread over white bread.
Select sweet potatoes over baked white potatoes.

Incorporate Fiber and Protein: Pairing carbohydrates with fiber, protein, and healthy fats slows digestion and lowers the meal's GL.

Focus on Portion Control: Even low-GI foods can have a high GL in large quantities. The GL framework naturally emphasizes appropriate serving sizes.

The Verdict: Why GL Is the Smarter Choice

While GI provides a basic understanding, GL offers a more practical and accurate assessment of a food's impact on blood sugar by including serving size. This makes GL a superior tool for managing blood sugar, energy levels, and weight. See Harvard Health for more on glycemic values.

Conclusion: Making Smarter Choices with GL

Focusing on Glycemic Load provides a more practical and nuanced approach to dietary management compared to the Glycemic Index. By incorporating portion size, GL offers a more accurate tool for controlling blood sugar, leading to more stable energy and reduced risk of chronic metabolic diseases. While GI has historical significance, GL offers the real-world accuracy essential for effective everyday health management.

Frequently Asked Questions

The primary difference is that the Glycemic Index (GI) only measures how quickly a carbohydrate raises blood sugar, while the Glycemic Load (GL) provides a more comprehensive measure by also factoring in the amount of carbohydrates in a standard serving.

Not necessarily. A high-GI food can have a low Glycemic Load (GL) if its typical serving size contains very few carbohydrates. For example, watermelon has a high GI but a low GL, meaning a normal portion won't significantly spike your blood sugar.

To calculate the GL, you multiply the food's Glycemic Index (GI) by the grams of available carbohydrates in one serving and then divide by 100. The formula is: (GI × grams of carbs) / 100.

Yes. A food with a low GI can still lead to a significant blood sugar increase if you consume it in a very large portion. This is why the Glycemic Load is a more practical tool, as it accounts for quantity.

You can lower the overall GL of a meal by pairing carbohydrates with protein, healthy fats, and fiber. These nutrients help slow down the digestion and absorption of sugar, resulting in a more moderate blood glucose response.

Yes, many studies suggest that low-GL diets can be effective for weight management. They tend to promote stable blood sugar levels, which can help control appetite and reduce cravings.

Yes, how you prepare a food can affect its glycemic response. For instance, cooking starchy foods like pasta for a longer time can increase its GI, as it makes the carbs easier to digest.

Many resources online provide lists of foods with their GI and GL values. Authoritative sources, such as those from academic institutions or health organizations, are the most reliable.