The glycemic index of food: Does basing the diet on this concept help us lose weight?

Surely you've heard of glycemic index, one more parameter that tells us about the quality of what we eat and the effect of a food on our body. Today we tell you what you need to know about this index and if your knowledge helps when you lose weight or it's just a myth.

What is the glycemic index?

The glycemic index is a value that is assigned to food to estimate its response in our body. Specifically the glycemic index (GI) represents the glycemic response of a food or preparation, that is, it tells us the speed at which the sugar of what we eat, converted into glucose, reaches our bloodstream.

It is taken as a reference of a high glycemic index glucose, which have a glycemic index of 100, and all those close to this value are foods that quickly raise our blood glucose, while those of low glycemic index are digested more slowly, producing a less accentuated curve in our blood glucose and raising it long after its consumption.

Thus, there are glycemic index tables that include high GI foods: between 70 and 100, medium GI: between 56 and 69 and low GI: between 0 and 55. These tables are prepared considering the amount of food hydrates and their absorption rate, however, they have their limitations.

How can we meet him

exist international glycemic index tables where we can get the value assigned to different foods. The last ones published are from 2008 and show us the GI of 62 common foods having previously analyzed tables and studies with data of more than 2400 foods.

In many cases the cooking method of the evaluated foods is detailed, since food processing including cooking can affect their glycemic response as a study in Jamaica points out.

In general, legumes, fruits and vegetables and dairy products are low glycemic foods, while breakfast cereals, bread and rice, can be placed under a category of high, medium or low GI depending on whether it is whole grain or whole grain bread or white rice and the ways of cooking them.

In all glycemic index tables Egg or meat of any kind is not included, as we have said, this value is extracted taking into account the amount of carbohydrates in food and both fish, poultry and red meat and eggs do not have this nutrient in their composition.

What science tells us about the glycemic index of food and weight loss

The glycemic index was long mentioned in diets for slim down, and although their knowledge can have a great influence on the prevention and control of different diseases, today we know that its usefulness is more limited than we thought.

Researchers in Australia have observed the usefulness of GI to control diabetes, weight gain, blood lipids and many other factors that tell us about metabolic health, demonstrating that this parameter can be valuable in addressing overweight and obesity. However, another small study published in The Journal of Nutrition concluded that reducing GI in a diet does not offer additional benefits to energy restriction when promoting weight loss in obese people. That is, it is the same if we have low or high GI foods at the time of weight loss.

The lack of consensus about the usefulness of the GI to lose weight is due to its variations due to multiple factors that make it a parameter that although guides us, is not definitive at all.

The multiple factors that affect the GI

We have already said that in order to create the GI tables, the proportion of carbohydrates of foods cooked in different ways is taken into account, so it is clear that carrots do not have the same effect on our glucose if we consume it raw and whole than if we eat it grated and raw or cooked and pureed.

Beyond cooking and processing of a food that affects the GI by reducing its fiber or facilitating its digestion, external factors such as other foods consumed may vary.

The food combination can affect the glycemic response of a food only and since we do not eat many foods in isolation but we include them in more complex dishes, with other ingredients, the GI loses noticeably utility, since it is very difficult to know the IG of a stew with meats, various vegetables and legumes even if we know the GI of each food separately.

As if that were not enough, like the IG it depends on the process of digestion and absorption of the hydrates of a food (or several), it can vary from one person to another as a study published in the journal Cell has shown something that reminds us of the great limitations of the IG at the time of losing weight.

The GI can serve, but never in isolation

While the IG has many limitations that can lead our diet as we lose weight, we must know that there is evidence of the multiple risks of eating high GI foods such as obesity, cardiovascular problems, infertility and others noted by the Harvard School of Public Health, while Low GI foods are associated with less inflammation and better metabolic health as an investigation published in 2014 concludes.

GI can help us improve the quality of what we eat to take care of health, but it should never be considered in isolation but together with other factors

Thus, GI can be taken into account when losing weight and can be of great help to guide us towards a better quality diet that protects health, but should never be considered in isolation. That is to say, we should not just decide based on the GI, but considering that other foods also influence and that for example an active person may receive better high-GI foods than a sedentary person or that those with diabetes would need even more low-GI foods than those who do not suffer from such disease.

If, in addition to the GI, we consider fats, proteins, fiber, the level of physical activity, the needs and other peculiarities of each one as well as the dishes and foods we eat, the use of this parameter can be useful, while deciding only on the basis of GI can lead to erroneous decisions when losing weight taking care of health.

Bibliography consulted | Diabetes care 2008 Dec; 31 (12): 2281-2283. //doi.org/10.2337/dc08-1239; Br J Nutr. 2006 Sep; 96 (3): 476-81; Am J Clin Nutr July 2002, vol. 76 no. 1 266S-273S; Am J Clin Nutr July 2002, vol. 76 no. 1 281S-285S; J. Nutr. October 1, 2005, vol. 135 no. 10 2387-2391; Cell, Volume 163, Issue 5, p1079-1094, November 19, 2015.
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