Glycemic index


In the past, it was thought that it is important how many carbohydrates are found in food, while in recent years this view has clearly changed. Today we know that the type of carbohydrates delivered has a decisive impact on training performance, on energy delivery during exercise, or even on the reduction of body fat. Even in the 1970s a carbohydrate group was divided in a pragmatic way roughly into two classes – a class of simple and complex carbohydrates. Thus, chocolate, biscuits, fruits and sweetened refreshing beverages were classified as simple sugars. They penetrate – according to contemporary claims of scientists – quickly into the bloodstream and thus lead to a rapid increase in the level of sugar in the blood. Complex carbohydrates, such as those derived from bread, rice, pasta and potatoes, lead to a slower increase in blood sugar, which was the recognition at that time. 


Glycemic index (IG) 

Dr. David Jenkins, nutritionist in Toronto, discovered in 1981 that it did not really correspond to reality. His main goal was to find the right sources of carbohydrates for diabetics. On this occasion, he discovered that products such as potatoes, which were traditionally included in complex carbohydrates, surprisingly quickly lead to a fairly high level of sugar in the blood. In contrast, it turned out that certain products that were actually known as simple carbohydrates could be included in products leading to a slow and lower than expected increase in blood sugar levels. It motivated scientists working with prof. Jenkins to establish the measure of how quickly and to what level will the level of sugar in the blood rise after eating a certain carbohydrate. The reference value was 100 grape sugar (glucose). All other carbohydrates were determined in relation to glucose. If a carbohydrate leads to a faster and higher increase in blood sugar than glucose, then the glycemic index (IG) is higher than 100. If a carbohydrate leads to a slower and lower increase in blood sugar than glucose, then the glycemic index is less than 100 (see Table 1). 



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Glycemic index (IG) and insulin levels 

How does IG help athletes in a fitness club reduce weight? To understand how IG affects fat reduction, first read some of the information on the hormone insulin. Insulin is secreted by the pancreas when the blood sugar level rises. This hormone lowers blood glucose, transporting sugar to muscle cells (where it is stored as glycogen, it is a form of carbohydrate storage) or is transported to fat cells, causing the growth of adipose tissue. However, without the action of insulin, as it happens in diabetics, the level of sugar in the blood would rise dangerously. Products that have a high GI lead to rapid and high blood glucose levels. As a result, there is also a large supply of insulin, as in the case of eating cornflakes or white bread. The fruit, on the other hand, due to the content of a large amount of fiber, leads to a slow increase in the level of sugar – and thus also insulin. Although insulin plays a vital role in maintaining a stable blood sugar level, too much of it causes feelings of lethargy and fatigue. Who does not know the feeling of “afternoon energy hole after eating a dinner consisting of, for example, potatoes and sweet dessert? It is thought that a sudden increase in insulin after eating dinner means that tryptophan is transported in a large amount by the aminocarboxylic acid to the brain. There, tryptophan is also converted into serotonin, a carrier that causes fatigue 12. 


Why insulin inhibits fat reduction 

Insulin is a hormone that is specifically designed to create inventories. Its role in the body is to store nutrients. It can store not only glucose. The same applies to fat. Insulin increases the activity of an enzyme called lipoproteinlipase (LPL), an enzyme responsible for storing fat in adipose tissue 6. Unfortunately, the action of insulin also goes the other way; it also inhibits fat reduction. This is done by inhibiting an enzyme called hormone-sensitive lipase (HSL). Therefore, in the case of a high level of insulin, the fat is burned less, but the carbohydrates are bigger. Simply put, we can say that a high level of insulin creates fat tissue! IG and sport 

IG is especially interesting for an athlete in a fitness club when it comes to how different nutritional products work on blood sugar before exercise. Most of the results of the experiments indicate, as expected, that the optimal fat burning occurs when we use low GI carbohydrates before the exercise, which will cause a small increase in insulin and blood sugar levels. 9, 10. Due to the small amount of insulin in the blood, fat reserves are consumed more. In 1979, scientists were able to document that glucose (the advertisement speaks of a “quick portion of energy in the meantime) given for 30 min. before training, it causes a rapid increase in the level of glucose in the blood and is accompanied by a naturally rapid increase in insulin, which significantly reduces the reduction of body fat during exercise 2. Reduced fat burning 

In principle, almost all studies indicate that carbohydrates of all kinds eaten before training lead to reduced fat burning. If we eat a meal rich in carbohydrates (eg spaghetti) even four hours before the workout, then the fat burning will be reduced to provide energy 5 compared to fat burning during fasting training. This is particularly true for high IG carbohydrates, but also to a lesser extent for low IG 8 carbohydrates. The new Dutch study also showed that glucose introduced into the body before training causes 34% lower fatty acid oxidation (fat burning). 1. So it is obvious that if we want to achieve the maximum training effect, we should provide our bodies with carbohydrates before training, because they provide energy in a more effective way than fats and are used as an energy source with increased physical effort. If, on the other hand, we want to change the fat tissue into energy (the body’s ability to use fat as a source of energy), we should give up providing the body with all carbohydrates before training. This also applies to the still-pleasing refreshing apple drink. Low GI products help reduce body fat 


The South African researchers found that selecting low GI foods increases weight loss and body fat during Diet 7. Two groups of people in the experiment received the same amounts of protein, carbohydrates and fat. However, one group was mostly carbohydrates with a low IG, the second group with high GI carbohydrates. Despite exactly the same energy value of the dishes, the group of people receiving low IG carbohydrates within 12 weeks lost approximately 2 kg more weight than the group receiving high IG carbohydrates (9.3 kg compared to 7.4 kg). This difference can be explained most probably by lower insulin levels in the group of people who used low IG carbohydrates. The next information comes from the work of the University of Loughborough in England 11. Participants in the experiment were given three hours before sporting activities carbohydrates with a high relative low IG with the same amounts of proteins, carbohydrates and fat. After 35 minutes, the insulin level after a meal consisting of high GI carbohydrates increased by an order of 10, that is by 1000% (!), While the insulin level after a meal consisting of low IG carbohydrates only by 80 to 160%. Then people after a low GI meal within three hours until the start of training burned almost 70% more fat than those in the second group with a markedly elevated level of insulin. In the physical exercise phase, fat burning at a low IG was even 118% higher. Thus, it is clear that high-carbohydrate carbohydrates lead by causing a large increase in insulin levels to markedly reduced fat burning and should therefore be avoided if our goal is to reduce body weight. Therefore, fruit, vegetables and fruit should always be in the foreground of our menu. These products cause the slowest increase in blood sugar levels. Wholegrain products lie in the middle of an acceptable range; sweets, bread, white flour products, etc. are naturally a big obstacle to reducing body fat. 


In principle, two important factors affect IG 

By combining the carbohydrate with fat, gastric emptying is delayed, and thus the level of sugar in the blood 4 is increased. Then IG has a lower value. However, you should never consciously combine fat with simple sugar to lower IG, unless it is high-quality vegetable oils (linseed oil, hemp oil, olive oil). Carbohydrate sources with a high fiber content are digested with a delay and for this reason show a lower GI. In addition, it is important that those who prefer low GI carbohydrates have more constant blood sugar levels and therefore experience less hunger pangs when using diet 3, which obviously has a positive effect on the reduction of body fat. If you are looking for a complete list of various IG products and can handle English, you can get information at http // 




Important when reducing body weight 

Stable blood sugar levels do not allow for the onset of wolf hunger attacks, it also allows sports training with reduced energy value of meals and optimally supplies the brain with fuel. Carbohydrate sources such as fruits, vegetables, shell fruit and whole grains are classic representatives of low GI carbohydrates. They lead to a more slow increase in insulin than, for example, white flour products, which also optimizes the reduction of adipose tissue. 

Sports training early in the morning (with a sufficiently low level of insulin) is the optimal solution to improve fat burning, because the body in this case first reaches its fat reserves. In the case of training during the day, the following rule applies for a few hours before training: carbohydrates should be consumed only with low GI and only in a limited amount (ca. 30 to 70 g), if the main goal is to reduce body fat. It is reasonable to eat, for example, a small portion of a fruit salad, 40 to 50 g of oatmeal with one fruit and skimmed milk, one slice of wholemeal bread with a thin cheese spread or a salad, eg with pieces of turkey or tuna with vinegar and olive oil. 


You can read also: Pre or post work out?

Posted on: February 13, 2019

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