A low glycemic index (low GI) diet is an eating plan based on how foods affect blood sugar levels, also called blood glucose levels.

The glycemic index ranks food on a scale from 0 to 100. At the lower end of the scale are foods that have little effect on blood sugar levels. At the top end of the scale are foods with a large effect on blood sugar levels.

A low GI diet uses the glycemic index as a primary guide for meal planning. People can also use the glycemic index as one of many tools for choosing foods and meals.


The purpose of a low GI diet is to choose foods that are less likely to raise blood sugar levels.

Why you might follow a low GI diet

You may choose to follow a low GI diet because you:

  • You want to lose weight or maintain a healthy weight
  • Need help planning and eating healthier meals
  • You need help keeping your blood sugar levels from being too high or too low as part of a diabetes treatment plan
  • You want to reduce your risk of diabetes or heart or blood vessel disease

The glycemic index

The glycemic index is intended to be a guide to food choices for people living with diabetes. An international database is maintained by the Glycemic Index Research Service at the University of Sydney in Sydney, Australia. The database displays the results of food research from around the world.

A basic overview of carbohydrates and blood sugar is helpful to understand low GI diets.


Carbohydrates, also called carbohydrates, are a type of nutrient in foods. The three main forms are sugars, starches and fibres. Your body breaks down sugars and starches from carbohydrates. They end up as a type of sugar called glucose. This sugar passes into the bloodstream and is the main source of energy for the cells in your body. Fiber passes through your body undigested.

Two main hormones from the pancreas help control blood glucose. The hormone insulin transports glucose from the blood into the cells. The hormone glucagon helps release glucose stored in the liver when blood sugar levels are low. This process helps keep the body fueled and blood sugar balanced.

Many different things about food affect how quickly glucose enters the bloodstream.

understanding GI numbers

The glycemic index classifies the effect a food has on blood sugar levels. A low GI diet implies foods that have low GI values. The categories are:

  • low GI: 1 to 55
  • Average GI: 56 to 69
  • High GI: 70 and above

To assign a rank, also called a GI value, researchers usually compare the effect of eating food with the effect of eating sugar on blood sugar levels. Sometimes the comparison is made to eating white bread. For example, to test GI value of a cantaloupe, 10 or more healthy people eat enough cantaloupe to absorb 50 grams of carbohydrates. That’s about one medium cantaloupe for each person. Over the next two hours, their blood sugar levels are tested several times. On another day, the same 10 people eat or drink 50 grams (12 teaspoons) of sugar. Again, their blood sugar levels are tested several times over the course of two hours.

The researchers compared the results of eating sugar to eating melon to rank the effect of eating melon. The GI the value for melon is 65 to 70.

Limits of GI values

The glycemic index does not take into account how much food you are likely to eat during a meal. For example, you probably wouldn’t eat a whole medium-sized cantaloupe in one sitting.

To focus on this problem, researchers developed the idea of ​​glycemic load (GL). This number shows the effect on blood sugar levels when you eat a common portion of food. For example, you can eat a third of a medium-sized cantaloupe in one meal. The GL the value for that much melon is around 11 or lower.

University of Sydney table GI values ​​also includes GL values. The GL values ​​are divided into:

  • low GL: from 1 to 10
  • Average GL: 11 a.m. to 7 p.m
  • High GL: 20 or more

Other questions

A GI value tells you nothing about other nutritional information. For example, melon has medium to high GI result and environment GL result. But it is a good source of vitamin C, beta carotene and other important nutrients. Whole milk has low GI value and low GL value. But it is high in fat and calories. So it may not be a good choice for weight loss or weight control.

The published GI the database is not a complete list of foods. Instead, it’s a list of foods that have been researched. Very nutritious foods with low GI the values ​​may not be in the database. The list also includes highly processed foods, which may be less nutritious than unprocessed foods. And some foods with low GI values ​​may not be good sources of nutrients.

The GI the value of any food product depends on many factors. How the food is prepared and processed matters. Also, there can be a range in GI values ​​for the same foods. So the values ​​may not be reliable for all foods.

Diet details

If you follow a low GI diet, your carb foods are mostly limited to low-carb choices. You will usually avoid foods with high values. Examples of low, medium and high foods GI the values ​​are:

  • low GI: Green vegetables, most fruits, raw carrots, beans, chickpeas and lentils.
  • Average GI: Sweet corn, bananas, raw pineapple, raisins, cherries, oat cereal, and multigrain, whole wheat or rye bread
  • High GI: White rice, white bread and potatoes

Commercial low GI diets can refer to foods as containing slow carbohydrates or fast carbohydrates. This is because you are feeding low GI value are digested and assimilated over a longer period of time. Foods with high values ​​are digested in a shorter time.


Studies of low GI diets show different results. In general, they have shown a low GI The diet can be helpful for:

  • Losing weight
  • Lowering blood pressure
  • Lowering total cholesterol levels
  • Improving diabetes management
  • Reducing the risk of diabetes and diseases of the heart and blood vessels

The researchers note that the dietary benefit may be related to the nutrient-dense and high-fiber foods in the studies. The overall nutritional quality of food may be more important than GI the value of each food product.

The bottom row

After a low GI diet can help you lose weight or maintain a healthy weight. It can help you manage a diabetes plan. It can reduce the risk of diabetes and heart and blood vessel disease.

The glycemic index can also be one tool, not the main tool, to help you make healthier food choices. The Dietary Guidelines for Americans recommend a focus on healthy dietary patterns and nutrient-dense foods.

A healthy eating pattern means making consistent healthy choices over time. The foods that fit this pattern vary. These include a variety of fruits and vegetables that provide vitamins, minerals and fiber. A healthy eating pattern also includes whole grains that are high in fiber and other nutrients. Beans, legumes, fish, low-fat dairy products, and lean meats are also good choices.


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