The low glycemic index diet (GI diet) is a diet to slim down based on the concept of the glycemic index (GI) also called glycemic index. According to scientific studies, the low GI diet could lead to weight loss, reduce blood sugar, lower the risk of heart disease and type 2 diabetes.
This article presents a detailed overview of the low-GI regime: what does it consist of, how to follow it and what are its advantages and disadvantages.
What is the glycemic index?
Carbohydrates (a term that refers to all carbohydrates) in bread, grains, fruits, vegetables and dairy products are an integral part of a healthy diet.
No matter what type of carbohydrate you eat, your digestive system breaks it down into simple sugars that enter the bloodstream.
Not all carbohydrates are equal because some types have different effects on blood glucose.
The glycemic index (GI) is an indicator that classifies foods according to their effect on blood glucose. It was created in the early 1980s by Canadian professor David Jenkins .
The rates at which different foods increase blood glucose are ranked in relation to the absorption of 50 grams of pure glucose, which is used as a reference food with a GI of 100.
- Low: 40 or less
- Average: 40-70
- High: 70 or more
Conversely, foods with a high GI should be limited because they are rapidly digested and absorbed, resulting in a rapid rise / fall in blood glucose.
It is important to note that only foods with carbohydrates have a GI. As a result, foods that do not contain carbohydrates, such as beef, chicken, fish, eggs, herbs, and spices, are not listed on GI listings.
Keep in mind : The Glycemic Index (GI) is a scale for classifying foods containing carbohydrates based on their effect on blood glucose.
What factors have an impact on the GI of a food?
Many parameters can influence the GI value of a food or a meal:
The type of sugar : it is a mistake to believe that all sugars have a high GI. The GI of sugars is actually 20 for fructose to 105 for maltose. As a result, the GI of a food depends in part on the type of sugar it contains.
Starch structure : starch is a carbohydrate composed of two molecules, amylose and amylopectin. Amyloidosis is difficult to digest, while amylopectin is easy to digest. Foods with a higher amylose content will therefore have a lower GI.
Carbohydrate refining : Preparation methods such as grinding and rolling have the effect of breaking amylose and amylopectin molecules, which increases the GI. In general, the more a food is processed, the higher its GI.
Nutritional composition : Fats and acids slow down the rate at which a food is digested and absorbed, which decreases GI. The addition of fats or acids, such as avocado or lemon juice, reduce the GI of a meal .
Cooking mode : Cooking and preparation methods can also change the GI. In general, the longer a food is cooked, the more its sugars are digested and absorbed quickly, which increases the GI.
Maturation : Unripe fruits contain complex carbohydrates that decompose as fruits ripen. The riper the fruit, the higher its GI. For example, an unripe banana has a GI of 30, while an overripe banana has a GI of 48.
The amount of carbohydrates is also important
The speed at which foods increase blood sugar depends on three factors: the type of carbohydrates they contain, their nutritional composition and the amount you eat.
However, GI is a relative measure that does not take into account the quantity of food consumed. He is therefore regularly criticized for this reason.
To solve this problem, the glycemic load (CG) has been developed.
GC is a measure of the influence of a carbohydrate on blood glucose, taking into account both the type (GI) and the amount (grams per serving).
Like GI, the glycemic load is classified into three categories:
- Low: 10 or less
- Average: 11-19
- High: 20 or more
GI remains the most important factor to consider when following the low glycemic index diet. However, it is also recommended to monitor GC.
It is advisable to ensure that the daily total of CG remains below 100. There are several databases to find the GI and CG of current foods. The reference site is that of the University of Sydney (in English). There is also the database in French site Montignac , less exhaustive, but very well designed.
Low GI diet and diabetes
Diabetes is a complex disease that affects millions of people around the world.
Diabetics are unable to effectively control their sugar levels, which can interfere with maintaining a healthy blood sugar level.
Good glycemic control can prevent and delay the onset of complications, including heart disease, stroke and nerve damage and kidney .
A number of studies indicate that low GI diets are useful for normalizing blood glucose in diabetics .
A study of 3,000 people with diabetes examined the effects of low and high GI diets on participants’ glycated hemoglobin (Hb A (1c)) levels. The concentrations of this molecule correspond to an average measurement of blood glucose over a period of three months .
The study found that levels of (HbA (1c)) were 6 to 11% lower for people who had a low GI diet than for those who had a high GI diet. In other words, low GI diets were associated with lower long-term glucose levels.
In addition, a number of studies indicate that high GI diets may increase the risk of type 2 diabetes by 8-40% .
A review of 24 studies on the subject has determined that for every 5 points of IG in addition, the risk of developing type 2 diabetes increases by 8% .
The low GI diet can also improve pregnancy in women with gestational diabetes mellitus, a form of diabetes that occurs during pregnancy.
It was also shown that a low GI diet reduced by 73% the risk of macrosomia (newborns weighing more than 4 kg at birth), associated with many complications for the mother and baby
Why focus on low GI foods?
Studies have shown that the low GI diet can also have other health benefits:
Improved cholesterol levels : Low GI diets have been shown to reduce total cholesterol by 9.6% and LDL cholesterol by 8.6%. LDL cholesterol is associated with an increased risk of heart disease and stroke .
May help with weight loss : Low GI diets have helped healthy adults lose 0.7 to 1.9 kg over a period of 5 to 10 weeks. The availability of research on the effects of long-term weight loss remains limited .
Can reduce cancer risk : people who eat a high GI diet are more likely to develop certain types of cancer, such as colorectal cancer and breast cancer, compared to people who diet low GI .
May reduce the risk of heart disease : a review of 37 studies found that people who follow a high GI diet are 25% more likely to develop heart disease than those who diet low GI .
What foods to eat with a low GI diet?
There is no need to count calories or track the amount of protein, fats or carbohydrates you eat with the low GI diet.
In contrast, this diet involves changing these dietary habits by replacing higher GI foods with others with lower GIs.
Here is a list of many healthy and nutritious foods recommended for the GI diet.
- Bread : complete, with cereals, rye and leaven.
- Breakfast cereals : oat flakes, muesli.
- Fruits : apples, strawberries, apricots, peaches, plums, pears and kiwis.
- Vegetables : carrots, broccoli, cauliflower, celery, tomatoes and zucchini.
- Starchy : sweet potatoes , corn, yams.
- Legumes : lentils, chickpeas, black beans, red beans.
- Pasta and noodles : pasta, soba noodles, vermicelli, rice noodles.
- Rice : Basmati, long grain rice and brown rice.
- Cereals : quinoa , barley, pearl couscous, buckwheat, semolina.
- Dairy products : milk, cheese, yogurt, custard, soy milk, almond milk.
The following foods are a staple of the ketogenic diet : they contain little or no carbohydrate and therefore have no GI. They can therefore be perfectly integrated into a low GI diet:
- Meats : beef, chicken, pork, lamb, etc. and the eggs.
- Fish and seafood : salmon, trout, tuna, sardines and shrimps …
- Nuts : almonds, cashews, pistachios, walnuts and macadamia nuts …
- Oils and fats : olive oil, rapeseed, etc. butter and margarine.
- Herbs and spices : salt, pepper, garlic, basil and dill
What are the foods to avoid?
Nothing is strictly forbidden with low GI diet.
However, try to replace as much as possible these high GI foods with low GI foods.
- Bread : white, Turkish bread, bagels, naan, standard chopsticks, Lebanese bread.
- Breakfast cereals : instant oats, corn flakes, and all puffed cereals.
- Starches : potatoes, instant mashed potatoes.
- Pasta and noodles : corn pasta and instant noodles.
- Rice : Thai, Arborio (used for risotto), medium grain white rice.
- Dairy substitutes : rice milk and oat milk.
- Fruit : watermelon.
- Salty snacks : crackers, pretzels, potato chips.
- Cakes and cookies : scones, donuts, cupcakes, cookies, waffles.
- Other : all sweets in general.
Disadvantages of low GI diet
Although the low GI diet has several advantages, it also has a number of disadvantages.
First, the glycemic index (GI) does not provide an accurate nutritional picture. It is also important to consider the fat, protein, sugar and fiber content of a food, regardless of its GI.
For example, the IG of french fries is 75, while a baked potato has a higher GI of 85.
In practice, there are many unhealthy low GI foods, such as ice cream (36-62), and custard (29-43). Low GI is therefore not equal to good and healthy for health.
Another disadvantage is that the GI measures the effect of a single food on blood glucose. However, most foods are consumed as part of a compound meal, making the GI difficult to evaluate.
Finally, as mentioned before, the GI does not take into account the number of carbohydrates you eat.
For example, watermelon has a high GI of 80 and is therefore not considered the best option when following a low GI diet.
However, watermelon also has a low carbohydrate content (6 grams of carbohydrates per 100 grams). In fact, a regular portion of watermelon has a low glycemic load (CG of 5) and a minimal effect on blood glucose.
This highlights the fact that the isolated use of the GI is not always the best indicator. It is also important to consider the carbohydrate content and CG of a food.
In summary : the low glycemic index diet has a number of disadvantages. GI can be difficult to calculate, it does not always reflect the quality of a food and does not take into account the number of carbohydrates consumed.
The final word
The low GI diet involves replacement of high GI foods with low GI ones.
It offers a number of potential health benefits, including normalizing blood sugar levels, helping with weight loss, and reducing the risk of heart disease and type 2 diabetes.
However, the diet also has several disadvantages.
In the end, it is important to have a healthy and balanced diet, based on a variety of whole and unprocessed foods, regardless of their GI.