Is Glycemic Index important for fat burning?

Author: Lera Truhanova - trainer and nutritionist.
2016-10-06

The key recommendation for nutrition for fat burning from a "guru" in the form of a trainer or an Instagram dietitian who has previously lost weight is often to reduce carbohydrates to extremely low amounts (1-2 g per kg of weight, for example). In other words - drying out.

But that’s not all. The carbohydrates that remain in the diet should be (as stated in many online sources) with a low glycemic index - otherwise, IT'S DISASTER: fat will not burn! This approach to the process of losing weight needs to be stopped at the root: firstly, because of the incompatible low amount of carbohydrates in the diet and, secondly, due to the unjustified nature of the method or misleading explanations.

Often in the very recommendations mentioned above, carbohydrates with a low glycemic index (GI) are advised to be preferred over others, justifying this by saying that their consumption will result in a lower blood sugar level and consequently a smaller release of insulin hormone. Excessive amounts of insulin often antagonize the fat-burning process. BUT! There are two very important nuances that are overlooked.

1. A comprehensive approach to these low-carbohydrate diets with glycemic index control should be taken into account: fats within 30-40 g for the entire diet (sometimes even less), 1-2 g of carbohydrates per kg of body weight, and 2-2.5 g of protein per kg of body weight (hello acidosis), or even higher.

2. It is important to remember that GI is not the key indicator of how a given product affects blood glucose levels.

Glycemic Load

Let’s start with the second point. There is Glycemic Index – a measure of the degree of increase in blood glucose levels after consuming a particular product, and there is:

Glycemic Load (GL) – an indicator that allows us to understand not only the degree of increase in sugar levels but also how long this level will remain at the upper limit.

For example, the GI of watermelon is 72, the GI of Snickers is 70, and the classic ice cream is 52. It's logically evident that Snickers and ice cream will provoke a larger insulin release, because they are sweeter, sugary, and more calorie-dense.

The formula for calculating GL is as follows: GL=(GI * amount of carbohydrates, g)/100.

Consuming products with a low Glycemic Index does not guarantee a stable level of insulin production (secretion) unless you take into account the Glycemic Load of the product.

But that’s still not all. In our diet, besides carbohydrates, there are also proteins and fats. Their consumption cannot go unnoticed at the hormonal level.

Comprehensive Approach to Nutrition

Now let's address the first point. An excess of protein in the diet completely undermines the logic of the approach to carbohydrates and their influence on blood glucose levels. Protein is a complex of amino acids, and hormones are derivatives of these amino acids. Thus, the consumption of protein food provokes various hormone reactions, including insulin. This happens not by increasing blood glucose but directly. If the amount of protein in the diet exceeds the norm, then there can be no talk of keeping insulin in check. BUT!!! A person on such a diet truly "dries out," and the process of fat burning occurs!

What’s the catch? The catch is that one could also lose weight with the same amount of carbohydrates per kg of weight but with a high GI. Fat burning would progress excellently even with a greater number of carbohydrates and a smaller amount of protein.

The main success factors are simpler than they seem:

• The total caloric content of the diet (the general rule: energy expenditure must exceed energy intake).
• The ratio of proteins, fats, and carbohydrates, ensuring the intake of all nutrients necessary for the healthy functioning of the body.
• A maximally enriched vitamin-mineral and amino acid composition of the diet.

And there is no room here for glycemic indicators. There’s no need.

Conclusion

Researchers at Tufts University (Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University) conducted a study in 2015 (the total duration of the experiment was about a year) in which they examined the effects of four different types of diets on the weight loss process:

1. Moderate carbohydrates (55% of total caloric intake). High GI.
2. Moderate carbohydrates (55% of total caloric intake). Low GI.
3. High carbohydrates (70% of total caloric intake). High GI.
4. High carbohydrates (70% of total caloric intake). Low GI.

In summary: subjects (91 people) were divided into 4 groups and adhered to their version of the diet for 22 weeks. During this time, as a percentage of total weight loss:

1. Group #1 lost 81% fat (of 100% total mass loss).
2. Group #2 lost 82% fat.
3. Group #3 lost 82% fat.
4. Group #4 lost 82% fat.

The metabolic rate after weight stabilization recovered almost uniformly. You can read more about the study in the original source.

The conclusion has already been voiced; briefly summarizing: the attention given to the ability of products to raise blood glucose levels is greatly exaggerated, and the theory of the dependence of the fat-burning process on the types of carbohydrates we consume (and in what quantities within daily caloric intake) has been refuted by logical reasoning and scientific facts.