Some say it helps to lose weight and improves health. Others, it is dangerous and has no scientific evidence behind it. What’s the truth behind all of it?
Intermittent fasting is a trend. And, as with almost all nutrition trends, it is accompanied by myths and biased information. Therefore, even if its starting point has a scientific basis, the message that ends up fishing among the population is distorted. Thus, it is advertised as an effective method of weight loss, or the population is confused by believing that it is all about alternating fasting periods with others in which there is an open bar. Neither one thing nor the other is true.
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To understand what intermittent fasting consists of, and what is scientific evidence supports it, we have consulted several US doctors and nutritionists, who have defined it as “voluntary abstinence from food and beverages in specific and recurring time periods with a constant rhythm”.
What do you get out of it? As the specialist explains, this rhythm “induces the coordinated alteration of metabolic mechanisms: fasting causes glucose to decrease in the blood and, therefore, the body resorts to fats as a source of energy; ketone bodies are thus generated, i.e. our body is subjected to a period of natural ketosis or nutritional ketosis [energy production through fat].”
Turning to fat instead of glucose as an energy source can be very interesting physiologically. However, it can also pose some risk, the doctors warn, since “if we raise ketones in the blood significantly, we can give rise to pathological states, such as alcoholic ketoacidosis or diabetic ketoacidosis.” Therefore, its first recommendation is that, if we want to start practicing intermittent fasting, we use an accredited professional to tell us how to do it without threatening our health.
Just one type of intermittent fasting?
It is easy that you have seen different proposals, all under the generic name of intermittent fasting. In reality, the options will depend, fundamentally, on three characteristics:
- The intensity: some methods require a strict fast; Others allow certain beverages to be taken during abstinence hours — infusions, broths… – or even some food.
- The periodicity: the frequency of the fasting intervals varies in some and other methods. Some are daily, but others propose three days a week.
- The duration: each proposal requires a variable number of hours followed by fasting.
From these parameters, the different fasts arise. Of these, the most popular, and also the most studied, is the one known as 16:8. It consists of limiting intake to a period of eight hours, followed by a fasting time of 16 hours. Let’s take a practical example: we have breakfast at nine, we make a strong meal at five o’clock and we’re out of lunch until the next day at nine.
“The scientific evidence is still few, but there are studies that conclude that intermittent fasting improves insulin resistance in patients with prediabetes or type II diabetes, and even decreases levels of diabetes-related glyced hemoglobin,” doctors explained. On the other hand, there is also some scientific conclusion [in short-term studies] about the improvement of symptoms of patients with multiple sclerosis; this would be due to the decrease in inflammation.”
With regard to cardiovascular health factors, there is conflicting information: while some studies suggest that parameters such as cholesterol or blood pressure seem to improve, others warn that “people who perform fasting periods in which they do not eat breakfast may present a higher risk of arteriosclerosis than those who have consistent breakfast.”
Regarding overweight and obesity, clinical studies have concluded that a daily calorie restriction on a conventional hypocaloric diet is as effective as a calorie restriction on intermittent fasting. Here it is important to note that research indicates that intermittent fasting, by itself, has no impact on weight loss; for this, you also need a caloric reduction.
It is essential, in this sense, to understand that the intake period after fasting can never be a license to eat as much as you want and the food you want. This is one of the myths surrounding intermittent fasting that contributes to losing credibility. If what is sought is health, we must eat healthy food.
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Before starting
As we’ve seen, intermittent fasting done right can be a good nutrition strategy. However, there are social, cultural and emotional aspects that we must also take into account and which may or may not advise us to implement it:
- The five-meal diet is rooted in our way of life and is easy for us to follow. In this sense, the introduction of intermittent fasting is controversial, since it will interrupt our biological rhythms and this can cause irritability, feeling hungry, sleep… So if you’re looking for weight loss, maybe it would be better to follow a low-calorie diet and avoid those annoying sensations.
- We must also bear in mind that, many times, to start a weight-reduction plan, we need to do ‘something different’ that motivates us. In that case, why not do intermittent fasting? Of course, it should always be supervised by a professional who knows how to start fasting and how to meet the nutritional needs of the patient.
- And another factor that we must anticipate is that fasting may be contraindicated in certain people. This is the case, for example, of “those who suffer from anxiety, a tendency to depression, stress, irritability problems, or those who are following a pharmacological treatment whose bioavailability may be compromised by being a certain number of hours without eating. And, of course, all those who have had or have an eating disorder”, warns the nutritionists.
Finally, it is important to remember that a successful nutritional intervention is based on achieving a change in the patient’s lifestyle, as well as in their habits.