A glycemic index diet is based on how foods affect your blood sugar levels. The glycemic index assigns a number to carbohydrate-containing foods based on how much blood sugar each food raises. The glycemic index is not a diet in itself. It is one tool among others to guide food choices.
A “glycemic index diet” refers to a specific eating plan that uses the index as the primary guide for meal planning. A glycemic index diet does not necessarily specify portion sizes or the optimal number of calories, carbohydrates, or fats for weight loss or weight maintenance.
The goal of a glycemic index (GI) diet is to eat foods containing carbohydrates that are less likely to cause large spikes in blood sugar. This diet helps you lose weight. But also to prevent chronic diseases linked to obesity. Like diabetes and cardiovascular disease.
Why You Might Follow the GI Diet
You might choose to follow the GI diet because you:
– want to lose weight or maintain a healthy weight
– need help planning and eating healthier meals
– want help maintaining blood sugar levels as part of a diabetes treatment plan
Studies suggest that a GI diet can help achieve these goals. However, you could achieve the same health benefits by eating a healthy diet, maintaining a healthy weight, and getting enough exercise.
The glycemic index
The GI principle was first developed as a strategy to guide food choices for people with diabetes. An international GI database is maintained by the Glycemic Index Research Services at the University of Sydney, Australia. This database contains the results of studies conducted in this city and other research centers around the world.
An overview of carbs, blood sugar, and GI values is helpful in understanding glycemic index diets.
Carbohydrates, or carbs, are a type of nutrient found in food. The three basic forms are sugars, starches and fiber. When you eat or drink something with carbohydrates, your body breaks down sugars and starches into a type of sugar called glucose. The main source of energy for your body’s cells. Fiber passes through your body undigested.
Two main hormones from your pancreas help regulate glucose in your bloodstream. The hormone insulin moves glucose from your blood to your cells. The hormone glucagon helps release glucose stored in your liver when your sugar (blood sugar) level is low. This process helps fuel your body and maintains a natural balance of blood glucose.
Different types of carbohydrate-containing foods have properties that affect how quickly your body digests them and how quickly glucose enters your bloodstream.
Understanding GI values
There are different research methods for assigning a GI value to foods. In general, the number is based on how much a food raises blood glucose levels compared to how much pure glucose raises blood glucose levels. GI values are generally divided into three categories:
low: 1 to 55
medium: 56 to 69
high: 70 and above
Comparing these values can therefore help guide food choices towards healthier foods. For example, a pastry made with white wheat flour has a GI value of 77. A whole wheat pastry has a GI value of 45.
Limits of GI values
One of the limitations of GI values is that they don’t reflect how much you’re likely to eat of a particular food.
For example, watermelon has a GI value of 80. This would put it in the category of foods to avoid. But watermelon contains relatively few digestible carbohydrates in a typical serving. In other words, you have to eat a lot of watermelon to significantly raise your blood glucose levels.
To solve this problem, researchers developed the idea of glycemic load (GL). A numeric value that indicates the change in blood glucose level when you eat a typical serving of the food. For example, a 120 gram serving of watermelon has a CG value of 5. Which would make it a healthy food choice. For comparison, an 80 gram serving of raw carrots has a CG value of 2.
The University of Sydney table of GI values also includes CG values. Values are usually grouped as follows:
Low CG: 1 to 10
Average CG: 11 to 19
High CG: 20 or more
Other questions about the glycemic index diet
A GI value tells us nothing about other nutritional information. For example, whole milk has a GI value of 31 and a CG value of 4 for a 1,250 milliliter serving. But due to its high fat content, whole milk is not the best choice for weight loss or weight control.
The published GI database is not an exhaustive list of foods. But a list of foods that have been studied. Many healthy low GI foods are not in the database.
The GI value of any food is influenced by several factors. Including how the food is prepared, how it is processed and what other foods are eaten at the same time.
Additionally, there may be a range of GI values for the same foods. Some would say that makes it an unreliable guide to determining food choices.
A GI diet prescribes meals consisting mostly of low-value foods. Here are some examples of foods with low, medium, and high GI values:
- Low: Green vegetables, most fruits, raw carrots, kidney beans, chickpeas, lentils, and bran breakfast cereals
- Medium: Sweet corn, bananas, raw pineapple, raisins, oat-based breakfast cereal, and multigrain, oat bran, or rye bread
- high: White rice, white bread and potatoes
GI diets can describe foods as having slow or fast carbohydrates. In general, foods with a low GI value are digested and absorbed relatively slowly, and those with a high GI value are absorbed quickly.
GI diets have varying recommendations for portion size, as well as protein and fat intake.
Depending on your health goals, studies on the benefits of GI diets have shown mixed results.
The results of a 16-year study that followed the diets of 120,000 men and women were published in 2015. Researchers found that high GL diets, resulting from the consumption of refined grains, starches and sugars, were associated with greater weight gain.
Other studies show that a low GI diet may also promote weight loss and help maintain weight loss.
Blood sugar control
Studies show that the total amount of carbohydrates in the diet is generally a stronger predictor of glycemic response than the GI. Research shows that for most people with diabetes, the best blood sugar management tool is carbohydrate counting.
A low GI diet can help people with diabetes control their blood glucose levels. Although the observed effects can also be attributed to the low calorie and fiber content of the diets prescribed in the study.
The review of trials measuring the impact of low-glycemic diets on cholesterol has shown fairly consistently that these diets can help lower total cholesterol. As well as low-density lipoproteins (the “bad” cholesterol). Low- to moderate-GI foods, such as fruits, vegetables, and whole grains, are generally good sources of fiber.
One theory about the effect of a low GI diet is appetite control. The idea is that high GI foods cause blood sugar levels to rise rapidly. A rapid response to insulin and a rapid return to hunger pangs. Low GI foods would, in turn, delay the feeling of hunger. Clinical research on this theory has yielded mixed results.
The final result
In order for you to maintain your current weight, you need to burn as many calories as you consume. To lose weight, you must burn more calories than you consume. The best way to lose weight is to combine calorie reduction in your diet. And associate it with an increase in your physical activity and exercise.
Choosing foods based on a glycemic index or glycemic load value will help you manage your weight. With products based on whole grains, fruits, vegetables.