The glycemic index is often perceived as a strict verdict on a product: a high index means no, a low one means yes. In practice, this is too crude of a simplification. For keto, LCHF, diets with carbohydrate metabolism disorders, and the development of sugar-free desserts, it is more important to understand not only the index itself but also the glycemic load of a specific portion.
The difference is fundamental. The glycemic index shows how carbohydrates from a product behave in comparison to glucose. The glycemic load answers a more practical question: what happens not with abstract 50 grams of carbohydrates, but with the portion that a person actually ate.
What is the glycemic index
The word “glycemic” is related to blood glucose. Glycemia is the level of glucose in the blood, and index is a benchmark that helps compare products with each other.
The glycemic index, or GI, shows how pronounced the rise in glucose is from a product compared to pure glucose. Glucose is conditionally assigned an index of 100. If a product has a GI of 50, it does not mean that blood sugar will rise by 50 units or in 50 seconds. It means that the carbohydrates from this product in a standard test provided about half of the glycemic response compared to the same portion of carbohydrates from glucose.
It is important to understand how this number is obtained. They do not test an arbitrary piece of the product, but rather an amount that typically contains 50 grams of available carbohydrates. After this, participants’ blood glucose is measured for about two hours and the area under the curve is compared to the response to pure glucose.
Therefore, GI is not equal to the usual absorption rate and does not describe the reaction of every person one-to-one. The actual response is influenced by metabolic health, insulin sensitivity, muscle mass, sleep, stress, physical activity, meal composition, and even the degree of processing of the product.
Why a high GI does not always mean a high load
A classic example is watermelon. It has a high glycemic index, often around 72. If you look only at this number, you might conclude that watermelon behaves almost like sugar. But watermelon contains a lot of water and relatively few carbohydrates per 100 grams of the product.
Herein lies the problem of the glycemic index: it compares 50 grams of available carbohydrates from the product, not a typical portion. To get 50 grams of carbohydrates from watermelon, you need to eat significantly more than just a small plate.
The same goes for an apple. If an apple has a GI of about 32, it is not about a small slice, but about the number of apples that would contain 50 grams of available carbohydrates. A typical portion can yield a completely different strength of response.
What is glycemic load
Glycemic load, or GL, takes into account two parameters: the glycemic index of the product and the amount of carbohydrates in a specific portion. Therefore, it is closer to real cooking, the plate, and the recipe.
The formula is simple:
| indicator | formula |
| glycemic load | GI × grams of available carbohydrates in the portion / 100 |
If a product has a high GI but few carbohydrates in the portion, the total load may be moderate. If a product has a medium GI but the portion is large and contains many carbohydrates, the load may turn out to be high.
Example calculation with watermelon
Let’s take 150 grams of watermelon. Suppose its glycemic index is 72, and it contains about 8 grams of carbohydrates per 100 grams of the product. In 150 grams, there will be about 12 grams of carbohydrates.
| step | calculation |
| carbohydrates in the portion | 8 g × 1.5 = 12 g |
| glycemic load | 72 × 12 / 100 = 8.64 |
| rounded result | GL about 8.6 |
This portion cannot be evaluated solely based on the high GI of watermelon. By glycemic load, it is closer to a moderate impact because there are not many carbohydrates in the portion itself.
How to read GI and GL in practice
For everyday product choices and for keto recipes, it is useful to keep a few rules in mind:
- the glycemic index shows the quality of carbohydrates, that is, their comparative glycemic response;
- the glycemic load shows the effect of a specific portion;
- the more carbohydrates in a portion, the higher the load at the same GI;
- fats, proteins, fiber, and acids in the dish can change the actual response of the body;
- individual reactions may differ, especially with insulin resistance, diabetes, lack of sleep, and low physical activity.
Therefore, the same product may be unsuitable in a large portion and quite acceptable in a minimal technological amount. This is especially important in cooking, where an ingredient may be used not as the basis of a dish, but as a tool for texture.
Why it is important to know this on keto
On keto, carbohydrates are usually counted, but glycemic load helps to look deeper. It shows not only the amount of carbohydrates but also what glycemic response a portion may give.
For a person with diabetes, prediabetes, insulin resistance, or unstable glucose, this can be an important guideline. But even without a diagnosis, GL is useful if the goal is to make low-carbohydrate nutrition more predictable.
This is especially true for sugar-free desserts. Simply removing sugar and replacing it with a sweetener is not enough. The recipe may still contain flour, starches, fruit purees, dairy products, nuts, cocoa, berries, and other ingredients that contribute different carbohydrate loads.
How to calculate the load of a recipe
For a finished product, the principle is the same, only the calculation is not based on one product but on the ingredients. First, the contribution of each carbohydrate ingredient is calculated, then the results are summed and recalculated per portion.
The order of calculation looks like this:
- list the ingredients that provide available carbohydrates;
- for each ingredient, determine the amount of carbohydrates in the recipe;
- multiply these carbohydrates by the glycemic index of the ingredient and divide by 100;
- sum the glycemic load of all significant ingredients;
- divide the total by the number of portions or recalculate per 100 grams of the finished product.
Eggs, butter, pure fats, many intense sweeteners, and other ingredients with zero or minimal carbohydrate load usually do not affect the GL calculation. They do not need to be forcibly included in the formula if they do not provide available carbohydrates.
Why a small amount of carbohydrate flour is sometimes acceptable
In low-carbohydrate baking, almond and coconut flour, psyllium, fiber, seeds, and nuts are often used. But sometimes a small amount of a more carbohydrate-rich ingredient, such as oat flour or a starchy component, may be needed for the desired texture.
This does not automatically ruin the recipe. The important factor is not the mere presence of such an ingredient, but its quantity in the finished portion and its contribution to the overall glycemic load. If it is used technologically, in a minimal volume, the final product can still remain low-carbohydrate and have a low load per portion.
This is why a professional approach differs from a simple list of prohibitions. The task is not to mechanically exclude all products with carbohydrates, but to understand their role, dosage, and final effect.
What affects the actual sugar response
Even an accurate GL calculation remains a guideline, not a personal forecast to the tenths. The actual response of the body depends on the context:
- insulin sensitivity and carbohydrate metabolism status;
- amount of muscle mass and physical activity;
- sleep, stress, and timing of meals;
- combination of carbohydrates with proteins, fats, fiber, and acids;
- portion size and eating speed;
- degree of processing and thermal treatment of the product.
Therefore, with diabetes and pronounced carbohydrate metabolism disorders, calculation does not replace glucose self-monitoring and medical recommendations. But it helps to see in advance where the main carbohydrate load is located in the recipe or diet.
Conclusion
The glycemic index is useful, but by itself, it can easily be misleading. It shows the reaction to a standard amount of available carbohydrates, not to a typical portion of the product.
The glycemic load is more practical: it links the index with the actual amount of carbohydrates in the portion. For keto, LCHF, and sugar-free desserts, this is especially important because it allows one not to fear individual ingredients blindly, but to calculate their contribution and manage the recipe consciously.
The main formula is simple: GL = GI × carbohydrates in the portion / 100. But the meaning of the formula is broader than arithmetic. It helps to move from fear of products to a precise understanding of what exactly and in what quantity affects glucose levels.
