Simple carbohydrates are the easiest and fastest forms of carbohydrates for the body to breakdown and utilize for energy. On the other hand, complex carbohydrates go through a longer breakdown process before they can be utilized for energy.
Why it matters
Within the body, carbohydrates circulate in our blood as glucose. The simple and complex carbohydrates we eat have an effect on the concentration of circulating glucose. The body constantly needs to regulate glucose concentration. If the body is unable to regulate glucose concentrations effectively, diseases like type II diabetes and obesity occur.
- Many factors will cause variations in the glycemic response from person to person.
- Physical activity significantly changes how the body will utilize glucose.
- The overall focus should be on consistently eating foods with a lower glycemic load (GL).
Simple carbohydrates are the easiest and fastest forms of carbohydrates for the body to breakdown and utilize for energy. On the other hand, complex carbohydrates go through a longer breakdown process before they can be utilized for energy. An example of a simple carbohydrate is sugar or glucose, which is the most abundant simple carbohydrate. Some common examples of complex carbohydrates are whole grains and starch (pasta, potatoes, etc.).
Within the body, carbohydrates circulate in our blood as glucose. The simple and complex carbohydrates we eat have an effect on the concentration of circulating glucose. This effect is known as the glycemic response to the food or carbohydrate which is measured by the glycemic index (GI) and glycemic load (GL).
Glycemic Index vs Glycemic Load
Glycemic index is a ranking of foods based on their measured blood glucose response compared with a reference food. The GI is defined as the increase in blood glucose level above the baseline which is the fasted state. The rise in blood glucose from baseline level is measured during a 2-hour period following the consumption of 50 grams of a test food carbohydrate.
The glycemic load is another method used to categorize foods by their effect on blood glucose levels. It is believed that GL provides a better indication of food choices because it takes into account the total quantity and quality of carbohydrates rather than a 50 gram portion of food. The GL is calculated by multiplying the GI of a food by the grams of carbohydrate per serving size. The higher the GL, the greater the expected increase in blood glucose.
The body constantly needs to regulate glucose concentration. If the body is unable to regulate glucose concentrations effectively, diseases like type II diabetes and obesity occur. In order for our body to regulate glucose concentration our muscles and fat cells need to be able to take in the glucose to be utilized for energy. This requires a facilitator known as insulin, which is produced by the pancreas and transports glucose into muscle and fat cells for use. This is where knowing the difference between simple and complex carbohydrates becomes important.
Effects of simple and complex carbohydrates on GI and GL
In general, simple carbohydrates are considered High-GI foods because they are digested quickly and will create a sharp increase in blood glucose. As a result, the pancreas rapidly releases insulin to meet the glucose demand. However, complex carbohydrates are considered Low-GI foods because they are broken down more slowly and released steadily into the bloodstream without causing a sharp increase or decrease in blood glucose. As a result, the pancreas releases a steady supply of insulin. Therefore, the foods with a lower GI will have a slower more sustained release of glucose (reduced need for insulin). Whereas, foods with a higher GI will have a larger and more immediate spike in glucose (increased need for insulin).
This is important to understand because if you continually eat simple carbohydrates that cause a rapid spike followed by a rapid fall of glucose in your system then the body will eventually become desensitized and produce less insulin. This then causes high amounts of glucose to circulate within the blood and eventually leads to type II diabetes, obesity, metabolic syndrome, cancer, and much more!
Variance of GI and GL
It is important to distinguish between what foods constitute simple and complex carbohydrates. In general, simple carbohydrates will have a higher GI compared to complex carbohydrates. An example list of foods and the corresponding GI and GL numbers is shown below.
Glycemic index & Glycemic load ranges
|Glycemic index||Glycemic load|
Additionally, the GI and GL of a given food will differ. For example, you will notice there is a stark difference in the GI of carrots compared to GL. This is because a half-cup of carrots is only 6 grams of carbohydrates. Research tells us that the long-term consumption of a diet with a relatively high GL is associated with an increased risk of obesity, type II diabetes and coronary heart disease.
GI & GL in common foods
There a many factors that will cause variations in the glycemic response from person to person. For example, the amount of carbohydrates in the meal, if the meal includes fiber, protein, and fat, what the previous meal was composed of, timing of the meal, physical activity level, choice of food, and glucose tolerance of the individual.
Physical activity significantly changes how the body will utilize glucose and it is often recommended to eat simple carbohydrates that have a higher GI around exercise (before & after) so the body can quickly utilize the glucose for energy. A meal that does not have a lot of carbohydrates will generally not have a dramatic glycemic response. Likewise, a meal that has fiber, protein, and fat will induce a slower glycemic response because these nutrients act like a buffer to the breakdown of glucose.
In all, the focus should be on consistently eating foods with a lower GL. In other words, eat carbohydrates that are more complex with a lower GL with most daily meals and eat simple carbohydrates with a higher GI mainly around physical activity (2-4 hours before & after). Limit simple carbohydrates outside of that.
Jon Esposito MA, CSCS, CISSN, USAW