Meaning of Glycemic Index

What is the Glycemic Index (GI)?

GI is the [blood glucose response] over a certain period of time after eating foods containing carbohydrates blood sugar against a reference such as glucose or white bread. Usually, the test amount is adjusted to provide the same amount of available carbohydrates.

Therefore, it is not an indicator that directly compares the portions we usually eat on a plate. It is a relative value that looks at the 'quality' of a food's carbohydrates under limited conditions.

How is GI measured?

Several people in a fasting state eat the test food and the reference food separately, and blood glucose is measured at regular intervals. The average is then calculated after computing individual responses.

Results may vary depending on the test subjects, methods, food varieties, and cooking states. This is why there are multiple values in the tables.

How are low, medium, and high categories divided?

Cut-off values are commonly used to divide categories, but health or disease cannot be distinguished by a 1-point difference at the boundary. This is due to measurement errors and food variations.

Categories are convenient tools for food comparison. Actual meals are mixed dishes and 1 serving size also differs from the standard test.

Why do cooking and processing have an effect?

Finely grinding grains or cooking them for a long time can make it easier for digestive enzymes to access the starch. Conversely, cooled starch, whole grain structures, and viscous fibers can alter the response.

The ripeness of fruit, the variety of potatoes or rice, and the degree of cooking also have an effect. A single GI is not fixed based on the name of the food alone.

Are the foods eaten together also important?

Proteins, fats, and fiber can affect gastric emptying and digestion speed, so the blood glucose response of a mixed meal may differ from a single-food table. The order of eating may also change some responses.

However, adding more fat to make the GI appear lower does not mean it is a healthy meal. Total energy and the quality of the fat must be considered together.

What is the difference between GI and Glycemic Load?

GI compares the response to a fixed amount of carbohydrates, while Glycemic Load (GL)reflects the carbohydrates in the actual amount eaten. For example, even if a food like watermelon has a high GI, the GL can be low if the carbohydrates in a typical serving size are small.

Conversely, eating a large amount of medium-GI foods can increase the total carbohydrates and the glycemic load.

How is this applied to dieting?

Rather than searching only for low GI, use it as a food selection tool to increase the proportion of vegetables, beans, whole grains, and less processed carbohydrates. Consider the serving size and total energy together.

This does not mean you can eat unlimited amounts of low-GI desserts or high-fat foods. satietyand long-term persistence are recorded.

Why do individual blood glucose responses differ?

Sleep, exercise, stress, insulin sensitivity, gut microbiota, and the timing of meals can change the response to the same food. Since the table shows group averages, it does not perfectly predict individual glucose meters.

Even small changes in a continuous glucose monitor (CGM) are not as definitive as food scores due to sensor lag and margins of error.

Precautions when treatment is required

diabetes People using medication or insulin should not arbitrarily adjust carbohydrate intake or medication dosages based solely on GI. Total carbohydrates, meal timing, and the action of the medication must be coordinated together.

If you experience recurrent hypoglycemia or clear symptoms of hyperglycemia, medical examination and education from healthcare providers take priority over internet GI tables.

Examples of how the same GI can mean different things on an actual plate

Eating a small amount of high-GI food may result in low total carbohydrates and glycemic load, while eating a large bowl of medium-GI food can increase the load. High-fat desserts may have a lower GI than expected, but their energy and saturated fatcalories can be high. This is why 'good foods' are not determined by GI rankings alone.

The principle of prioritizing less processed, fiber-rich foods, such as whole grains, beans, and vegetables, is a practical way to improve carbohydrate quality without having to calculate the GI every time.

Items to check when using a GI table

Check the variety and cooking method of the tested food, the reference food, the study subjects, and the range of values. Also, check if the cooking state and serving size consumed in Korea match the table. If there are multiple values, do not choose one as an absolute value.

If the results differ from your personal blood glucose records, do not conclude that the table is wrong or that your body is failing. Review your sleep, exercise, meal combinations, and measurement errors, and look for repeating patterns.

If you keep comparative records, try to match conditions as much as possible, such as the same amount, similar cooking methods, and the same time of day. Rather than a single peak value, recording pre-meal levels, post-meal changes, satiety, and intake for the next meal will help you find more useful patterns for food selection.

How should I read the numbers in the GI database?

Do not look only at the number next to the food name; check the variety used in the test, the degree of cooking, and the reference food. Even for the same rice or potato, multiple values may be presented if the starch structure or cooking state differs. If a value is presented as a range, use it based on the possibility of fluctuation rather than fixing a single middle number as the 'correct' answer.

You must also verify if the foods consumed domestically are the same as the test foods used in overseas research. If a GI with a similar name is applied to a food with different processing methods or sugar and fat compositions, the margin of error increases. For foods without available data, it is safer to observe the actual amount, raw ingredients, and post-meal reactions rather than estimating a number.

Commonly overlooked factors when choosing low-GI foods

Some processed foods may appear to have a low GI because fats or sugar alcohols have been added. In such cases, you must separately consider the total calories, saturated fats, digestive discomfort, and actual intake amount. A 'low GI' label is not a guarantee that there is sufficient protein and dietary fiber or that it is automatically advantageous for weight loss.

Conversely, high-GI foods can be used depending on the amount and context. You may consider the needs before and after exercise, digestive status, and overall meal composition; healthy foods are not placed on a forbidden list based on a single number. It is easier to verify effects by adjusting frequently eaten staple foods to less processed forms and realistic portions.

When blood glucose records differ from the GI table

First, check the amount eaten, the cooking method, foods eaten together, pre-meal blood glucose, and the time of measurement. Also, note the previous night's sleep, recent exercise, and stress. Do not conclude the effect of a single food by comparing two measurements taken under different conditions.

If you are undergoing treatment for diabetes, please show recurring patterns of hyperglycemia or hypoglycemia, along with the timing of your medication, to your medical staff. You must not personally change the dosage of insulin or glucose-lowering agents simply because the GI differs from expectations. Symptoms requiring diagnosis should be confirmed through standard blood glucose tests rather than GI experiments.