Many restrictive diets recommend cutting out high-glycemic index carbohydrates, those that are quickly absorbed by the body, such as white bread, because of the belief that this type of carbohydrate makes you fat.
However, a study published in the journal Advances in Nutrition shows that when it comes to weight gain or loss, there seems to be no difference between consuming high glycemic index or low glycemic index carbohydrates. This study is funded by Grain Foods Foundation (Association of Members of the US Bakery and Grain Milling Industries).
First of all, understand the glycemic index
Carbohydrates make up a large part of our diet. However, the carbohydrates present in foods are not all the same, both in terms of their chemical composition and the speed at which they are digested and absorbed by the body. That’s where the Glycemic Index comes in.
The glycemic index was introduced in 1981 as a method to classify foods according to their effects on postprandial blood glucose (ie, blood glucose levels minutes after meals).
This method compares the glycemic response of consuming 50 g of carbohydrate from a particular food, in relation to the same amount of a standard food, which is usually white bread.
Foods with a high glycemic index have their carbohydrates absorbed more quickly (called fast-absorbing carbohydrates) and those with a low glycemic index are absorbed more slowly.
It is important to remember that the glycemic index is measured when food is eaten alone, which is rarely the case in real life. We know that eating food together with other foods can change the glycemic index.
This can be very important for people living with diabetes, as they can consume foods with a high glycemic index at more appropriate times and in conjunction with other foods that help to slow down the absorption of carbohydrates. For example, eating bread alone is different from eating bread with cheese. In the latter case, carbohydrates will be absorbed more slowly, avoiding a blood glucose spike.
Do foods with a high glycemic index make you fat?
Since the discovery of the glycemic index, many scientific articles have been published on the topic and several popular books extol the supposed benefits of a low glycemic index diet for weight control and obesity prevention as well.
This hypothesis is explained by some findings that show high glycemic index meals resulting in greater insulin secretion and less postprandial fat oxidation than low glycemic index meals.
However, despite this explanation and the perception that low glycemic index foods promote weight loss and prevent obesity, science has shown controversial results. While some reviews show that a diet high in high-absorbable carbohydrates is implicated in weight gain, others do not indicate an association with body weight.
Thus, to clarify whether the glycemic index is important for weight control, the authors of the article performed a review of research in scientific databases for observational studies comparing BMI with a high or low glycemic index diet.
Data from 43 cohort studies (those that follow research volunteers for a certain period of time) from 34 publications, totaling 1,940,968 people evaluated, revealed no differences in BMI when comparing groups with high glycemic index and low index diets glycemic.
More specifically, it was seen that in 27 cohort studies, 12 did not show differences in BMI between the high or low glycemic index food groups and 7 indicated that the BMI was lower in the higher glycemic index groups. Thus, in 70% of the 27 cohorts, the glycemic index was not associated with BMI. In only 8 of the 27 cohorts, BMI was significantly lower in the group that had a low glycemic index diet.
The results demonstrated that the low glycemic index diet was not better than the low glycemic index diet for weight reduction.
A notable exception is that low glycemic index diets resulted in weight loss in glucose-tolerant adults but not glucose-intolerant adults.
From this, the researchers observed that there is little difference in how high and low glycemic index foods affect body weight and that the glycemic index, as a measure of carbohydrate quality, appears to be relatively unimportant as a determinant of BMI or of weight loss.
Instead of the glycemic index focus on healthy eating
Contrary to what many people think, the results of this study show that eating a diet with high glycemic index foods does not make a person more likely to gain weight or have obesity compared to a diet rich in low glycemic index foods.
Of course, more studies are needed, as the surveys analyzed have limitations, and without industry funding.
But I also don’t mean that the glycemic index should be left out. This is an interesting and important methodology, especially for people who suffer from diabetes. However, it doesn’t seem to be a good indicator of weight loss.
And if weight loss is your goal, it’s best to shrug off certain nonsensical dietary rules, like cutting out high-glycemic or fast-absorbing carbs, or whatever.
Don’t demonize carbs! They are important for the proper functioning of our body and our brain. If you’ve been on restrictive diets and eliminated carbohydrates from your life for a while, you know what I’m talking about.
Therefore, regardless of the type, carbohydrates can and should be part of healthy eating. You don’t need to say goodbye to bread or stay away from sweets.
You can eat everything (but not everything!) in moderation and without stress, always cultivating a peaceful relationship with food and with the body.
Find your balance, without the paranoia of an ideal weight or “perfect” body. Instead, focus on seeking your healthy weight, gained gradually and as a result of habits that provide quality of life.