Carbohydrates are frequently demonized in popular diets. For example, the ketogenic diet eliminates nearly all carbohydrates, and there are also many low-carbohydrates diets like the Atkins diet and South Beach diet.
Low-carb diets can be healthy for some people, particularly because they encourage the elimination of processed and refined grains, high-fructose corn syrup, and other simple sugars. These types of simple sugars, when added to foods, are associated with adverse health conditions
However, not all carbohydrates are necessarily bad for you.
Following a low glycemic diet can be a great way to take advantage of the health benefits of nutrient-dense carbohydrates like whole grains, legumes, and vegetables while avoiding unhealthy refined carbohydrates that can cause blood sugar spikes.
In this article, we will discuss the glycemic index, low-glycemic foods vs. high-glycemic foods, and how to follow a low-glycemic diet. We also share a sample low-GI diet plan to give you some ideas of what to eat on a low-glycemic diet.
We will cover:
- What Is the Glycemic Index?
- What Is a Low Glycemic Diet?
- What Affects the Glycemic Index of a Food or Meal?
- Benefits of a Low Glycemic Diet
- What Can You Eat On a Low Glycemic Diet
Let’s get started!
What Is the Glycemic Index?
Carbohydrates are one of the three primary macronutrients, alongside proteins and fats. They are found in foods like grains, fruits, legumes, vegetables, dairy products, cereals, and sweets.
Carbohydrates are formed by chains of sugar molecules. “Simple“ carbohydrates have simple sugars, which means that the sugar molecules are already quite small. Examples of simple sugars found in foods include glucose, fructose, lactose, sucrose, maltose, and galactose.
These carbohydrates consist of either one (monosaccharides) or two (disaccharides) sugar molecules bonded together.
Many sugar molecules can also bond together, forming long chains called polysaccharides. In this state, carbohydrates are typically considered a “starch.”
When you eat any carbohydrate, the body breaks down the molecule into its constituent simple sugars, the monosaccharides, such as glucose, which then enter the bloodstream.
Depending on the food source, the molecular structure of the carbohydrates in the food will vary.
Foods that contain mostly simple sugars are digested very rapidly because the carbohydrate molecules are already very small, existing primarily in the monosaccharide or disaccharide states. This leaves very little digestive work for the body to do before the sugars can be released into the bloodstream.
On the other hand, complex carbohydrates are broken down much more slowly. The long chains of starch have to be broken down to release each individual simple sugar molecule that is bonded together to form the long chains of polysaccharides.
Complex carbohydrates also typically contain fiber, such as cellulose, which takes much longer to digest and break down, causing a very slow release of the constituent sugar molecules into the bloodstream.
The glycemic index is a measurement system that basically scores or ranks foods based on the effect they have on your blood sugar levels after eating them.
Every given food that has a known glycemic index score is ranked based on how quickly it increases blood sugar levels compared to absorbing 50 grams of pure glucose, which has a reference value on the glycemic index of 100.
The glycemic index was developed by a Canadian professor, Dr. David Jenkins, in the early 1980s. It has since been used and expanded upon as more carbohydrate-based foods have been studied and compared to the absorption rate of pure glucose.
You can find the glycemic index of different foods in this database.
What Is a Low Glycemic Diet?
A low glycemic diet aims to consume foods that are categorized as “low glycemic” according to the glycemic index.
The glycemic index ranges from 0-100, with 100 being the maximal, rapid blood sugar spike that can come from eating simple sugars like white sugar.
The higher the percentage of simple sugars in a food, the higher the glycemic index will be because the sugars in the food will be rapidly digested and circulated into the bloodstream.
This will cause a quick rise in blood sugar because all of the sugars are released quickly.
Low-glycemic foods are considered to be those with a glycemic index of 55 or less. A glycemic index score of 56–69 is medium glycemic food, and high-glycemic foods have a GI of 70 or above.
A low glycemic diet places the emphasis on eating foods that have a low GI value because the lower the glycemic index value, the slower and smaller in magnitude the increase in blood sugar levels after eating it.
This is ideal because when blood sugar levels rise too quickly or too steeply, too much insulin can be released from the pancreas.
Insulin is the hormone that is necessary for the cells in the body to take up glucose from the bloodstream. Without insulin, or when you are insulin resistant, and your body is no longer sensitive to insulin, blood sugar remains in circulation even if your cells need it.
Essentially, insulin helps the cells detect that there is glucose available in the blood and then helps get glucose into the cells.
However, when there is a rapid and significant rise in blood sugar levels, the resultant insulin production and secretion can be disproportionately high, causing too much of the blood glucose to be taken up by various body cells.
This can actually cause blood sugar levels to drop too low, termed reactive hypoglycemia, leaving you feeling fatigued, tired, hungry, and dizzy, and experiencing a myriad of other symptoms of low blood sugar even though you just recently ate.
This is what we commonly referred to as a “blood sugar crash.“
Furthermore, over time, diets that contain a lot of high-glycemic foods have been shown to cause weight gain and an elevated risk of obesity, type 2 diabetes, insulin resistance, metabolic syndrome, heart disease, and stroke.
Lower-glycemic foods help keep your blood sugars stable because the carbohydrates within them take longer to break down, which means that the sugars that are eventually yielded are released more slowly into the bloodstream rather than all at once.
What Affects the Glycemic Index of a Food or Meal?
There are different factors that can affect the glycemic index value of an individual food or composite meal, including the following:
The Primary Type of Sugar
Interestingly, different types of sugar have different GI values.
For example, fructose has a glycemic index score of only 23—making fructose a low-glycemic food even though it’s a sugar—while sugars like maltose have a GI value of 105, which exceeds that of the general glycemic index.
Therefore, it’s helpful to pay attention to the primary type of sugar in a food.
How Refined the Carbohydrate Is
Refined carbohydrates are typically high-glycemic foods because the processing removes a lot of the fiber and essentially preemptively partially degrades the food, making the sugars enter the bloodstream much faster.
The Structure Of the Starch
Any starchy carbohydrate will be digested more slowly than a simple carbohydrate, such as those found in fruit juice, candy, or jelly.
Therefore, the GI of a starch will be lower. However, different plant-based foods have different structures of the starch within the food. Starch is composed of amylose and amylopectin, which are two different types of molecules.
When the starch has a higher percentage of amylose, the glycemic index of the food will be lower because amylose is more difficult to digest than amylopectin, causing a slower release of glucose into the bloodstream.
Overall Nutrient Profile of the Food or Meal
Eating a food that is primarily simple carbohydrates in isolation will have the most significant impact on your blood sugar levels. For example, drinking 8 ounces of apple juice will rapidly increase your blood sugar, and the overall G.I. of your “meal“ will be very high.
However, eating carbohydrates alongside other macronutrients, namely foods with protein and fat, in a given meal will slow the glycemic response to the carbohydrates because the other nutrients that enter the stomach at the same time cause the entire digestive process to slow down, thus releasing glucose into the bloodstream more slowly.
The ripeness of a fruit can have a significant impact on the glycemic index of the food. The riper the fruit, the higher the GI value.
Generally speaking, cooking food for a longer period of time increases the glycemic index value because it breaks down the starch and disrupts the amylose and amylopectin molecules. Therefore, the sugars in the food will be digested and absorbed more rapidly.
Interestingly, the amount of a given carbohydrate food that you consume does not affect the glycemic index value, which is one of the criticisms of the glycemic index. The GI is really just a relative measure of the rate at which a carbohydrate affects your blood sugar.
To better take into consideration the overall effect of eating carbohydrates, the glycemic load (GL) has subsequently been developed.
In addition to considering how the carbohydrate affects your blood sugar (glycemic index value), the glycemic load also considers the quantity of the carbohydrate, in terms of grams, that you ate.
The three classifications for the glycemic load are as follows:
- Low Glycemic Load: 10 or less
- Medium Glycemic Load: 11–19
- High Glycemic Load: 20 or higher
The recommendation for overall health is to keep your total daily glycemic load to 100 or less.
Benefits of a Low Glycemic Diet
There are several benefits of following a low glycemic diet, namely in its potential to reduce the risk of insulin resistance and diabetes. By eating low glycemic foods, you can prevent rapid and high blood sugar spikes and subsequent high insulin levels.
Studies have found that following a low glycemic diet can be effective at reducing blood sugar levels in those with diabetes and can help reduce hemoglobin A1C, which is a marker of long-term blood sugar levels.
Perhaps unsurprisingly, studies have also found that diets high in high glycemic foods increase the risk of developing type 2 diabetes.
Well-controlled blood sugar levels have been shown to help prevent adverse sequelae of diabetes, including nerve damage, kidney damage, heart disease, and stroke.
Low glycemic diets can also improve cholesterol levels, decrease the risk of heart disease and stroke, support weight loss, and may reduce the risk of certain cancers.
What Can You Eat On a Low Glycemic Diet
There are no rules or stipulations in terms of how many calories you can eat on a low glycemic index diet plan, nor is there a need to track your macros (carbohydrates, protein, and fat).
Rather, the goal with a low glycemic index diet plan is to follow a healthy, well-balanced diet with nutritious protein and fats and to make sure the carbohydrates you eat are low GI foods.
In addition to consuming lean proteins such as fish, poultry, lean meat, tofu and soy, and seafood, focus on eating healthy fats like avocado, nuts, nut butters, olive oils, and coconut.
Herbs and spices should be encouraged.
In terms of carbohydrates, a low glycemic index diet plan should include legumes like lentils, chickpeas, and beans along with whole grains like steel-cut oats, bran cereals, soba and buckwheat noodles, quinoa, teff, amaranth, and freekeh. Low-sugar dairy foods such as Greek yogurt, cheese, and cottage cheese are encouraged.
All fruits and vegetables can be part of a low glycemic index diet plan but focus on low-sugar fruits and non-starchy vegetables such as melons, tomatoes, kiwi, apricots, berries, citrus fruits, asparagus, leafy greens, cucumbers, celery, green beans, broccoli, artichokes, mushrooms, and butter beans.
Remember that the ripeness of the fruit affects the GI value, and consuming higher-sugar fruits, such as bananas, with a fat, such as nut butter, will reduce the GI of the food.
Avoid refined grains, sugars, jelly, candy, syrups, ice cream, and other sweets.
Most of all, try to pair your carbohydrates with proteins and fats for slower absorption of blood sugar.
If you are looking to cut out sugar altogether, check out our article on How To Sugar Detox.