Foods with a high glycemic index (GI) raise blood sugar quickly and may cause health issues if someone eats too many of them. Eating a low GI diet may help to prevent and manage diabetes and cardiovascular disease. A person may also manage their weight with a low GI diet as part of an overall healthful eating approach.
This article explains what the GI is, and which foods are high and low GI items. It also outlines the benefits of a low GI diet and gives an example of a low GI meal plan.
The glycemic index (GI) is a measurement that ranks foods containing carbohydrates according to how much they affect someone’s blood sugar. The International Organization for Standardization (ISO) rank foods from 1–100 and use pure glucose, with a GI of 100, as a reference.
The Glycemic Index Foundation (GIF) classify the GI of foods as either low, medium, or high:
- low GI is 55 or less
- medium GI is 56–69
- high GI is 70 or greater
The American Diabetes Association provide a list of common foods and their GI. They note that some sources use white bread as a reference point instead of pure glucose.
Glycemic load (GL) is another measurement that some experts believe gives a more realistic picture of how foods affect blood sugar. GL considers the amount of carbohydrate in a portion of food, as well as its GI.
People can use the glycemic index to help them choose healthful foods and monitor how much sugar and carbohydrates they eat. This approach can help someone manage their weight or a health condition such as diabetes.
The GIF explain that several factors influence how fast a particular food raises someone’s blood sugar. These factors can include:
- how refined the carbohydrate is
- the physical and chemical structure of the food
- the cooking method
- how much fiber the food contains
- how much protein, fat, and acid the food contains
Generally speaking, refined and processed carbohydrates metabolize into glucose more quickly. Foods with fiber, protein, and fats release glucose more slowly, so they have a lower GI. Longer cooking times can break foods down, which means that someone consuming those foods absorbs glucose quicker.
Someone who wants to manage their weight or diabetes can find out the GI of foods from the International Tables of Glycemic Index and Glycemic Load Values. According to the table, the following foods are high in GI:
- white and whole wheat bread
- white rice
- breakfast cereals and cereal bars
- cakes, cookies, and sweet treats
- potatoes and fries
- chips and rice crackers
- fruits such as watermelon and pineapple
- dried fruits such as dates, raisins, and cranberries
- sweetened dairy products such as fruit yogurts
People following a low GI diet can eat foods with a medium GI of 56–69, but less frequently than low GI foods. Food with a medium GI includes rye bread and raisin bran cereal.
High GI foods tend to spike a person’s blood sugar, causing their body to produce more insulin. After insulin shunts glucose into cells, a person’s blood glucose can drop, leaving them feeling low in energy or mood.
Besides those short-term effects, dysregulated blood glucose can have longer-term health effects such as insulin resistance and diabetes.
According to the International Carbohydrate Quality Consortium (ICQC), there is a consensus that diets low in GI and GL are relevant to the prevention and management of diabetes, coronary heart disease, cancer, and probably obesity.
Research suggests that a low GI diet may be beneficial and help prevent some health issues.
Being aware of the GI of foods may help people control their blood sugar and prevent or delay complications relating to diabetes. Research suggests that low GI diets may help people with diabetes lower their blood sugar levels.
A 2019 review notes that low GI diets can reduce long-term markers of blood sugar control, body weight, and fasting blood sugar levels in people with prediabetes or diabetes.
A low GI diet may also help with gestational diabetes. This is a condition where someone develops high blood sugar while pregnant, which usually resolves after they give birth.
A 2016 meta-analysis suggests that for people with gestational diabetes, eating a low GI diet may reduce the risk of macrosomia. This is a condition that results in larger-than-average babies, which can lead to numerous short- and long-term complications for both the person giving birth and the baby.
A 2014 study suggests that in addition to controlling glucose and insulin metabolism, a low GI and energy-restricted diet may also help to reduce body weight.
High GI foods may also affect mood and energy. A 2016 study indicated that among healthy weight and adults with overweight, eating a high GL diet resulted in a 38% higher likelihood of depressive symptoms and a 26% higher score for fatigue and inertia.
A 2019 meta-analysis indicates a relationship between high GI and GL diets and coronary heart disease. Another 2019 meta-analysis notes an association between a high GI diet and colorectal, bladder, and kidney cancers.
The following are examples of meal options for someone following a low GI meal plan:
Some low GI breakfast options may include:
- scrambled eggs with smoked salmon
- buckwheat pancakes with berries
- breakfast quesadillas with black beans, spinach, and mushrooms
Low GI lunch options can include:
- black bean soup
- mango chicken and almond on rye bread
- cauliflower and celeriac soup
Low GI dinner options can include:
- lamb shanks with barley, garden peas, and mint
- Tex-Mex tofu soft tacos
- Indian-style spiced vegetable and cheese parcels
Low GI snack options can include:
- a slice of cinnamon, oat, and almond loaf
- homemade full-of-fruit muffins
- roasted soy nuts
When planning meals it may prove useful to count carbs. By managing carbs using the GI, people may be able to better control their blood sugar levels.
A person may find following a low GI diet somewhat complicated. A person needs to know the GI of all the foods on their plate, which can prove problematic when a meal has many ingredients. Following a low GI diet can limit what options someone has when eating out in restaurants.
A person also needs to consider the amount of fiber, fats, and protein in a meal to see how much the meal as a whole may affect their blood glucose.
A 2015 study advises that people need to consider low GL and GI in the context of overall healthful eating. According to a 2018 review, fiber and whole grains are essential components of a healthful diet and may predict health outcomes better than GI.
Therefore it may be more important for people to be conscious of the GI of foods while maintaining a balanced and healthful diet.