The fast intermittent is an eating pattern in which longer than usual periods without eating – for example, twelve or more hours – alternate with cycles of food intake. One of the best known intermittent fasts is the time of food restriction 8/16.
This means that one can consume food within eight hours of the day – for example, between 10 and 18 hours-, while fasting for 16 hours every day.
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The doctor Gonzalo Cruzresearcher at Center for Integrative Neurobiology and Pathophysiology, CENFIof the Valparaiso Universitywarns about the metabolic effects of intermittent fasting.
“There are several studies in people and also in experimental animals that show beneficial effects of intermittent fasting on the metabolism of lipids and carbohydrates. For example, an improvement in glucose tolerance, blood glucose levels, LDL cholesterol, triglycerides and even blood pressure has been observed. Interestingly, these effects are seen even without significant weight loss.»
caloric restriction
One of the most frequent questions about intermittent fasting is its effect regarding the decrease in body weight, since, usually, people look for this type of strategy to lose weight.
“A recent clinical study showed that the effects of intermittent fasting are lost if the person overeats to compensate for what they did not eat during the fast, that is, if they fast without caloric restriction, concluding that it is caloric restriction and not fasting that has the beneficial effects on body weight and metabolism. However, the logic of this study is not what intermittent fasters usually do, since those who want to lose weight must be in a caloric restriction. So the correct question is whether caloric restriction with intermittent fasting or without intermittent fasting has better effects.”
In this context, the researcher adds that a recently published article attributes most of the beneficial effects of caloric restriction to prolonged periods of fasting (Pak, 2021). That is, you have better metabolic effects if the calories are consumed within a limited time range.
healthy longevity
Several studies have also shown that in various species, such as bacteria, worms and even rodents, periods of intermittent or prolonged fasting increase lifespan.
“The key is in the beneficial effects of intermittent fasting in preventing cellular aging and generating a metabolic switch towards routes that allow energy and life to be conserved. The mechanisms that explain these observations are still under study. However, the various types of intermittent fasting have shown beneficial effects, many similar to those produced by physical exercise during aging.
Along the same lines, he notes that our biological clocks are strongly influenced by two main factors: the light/dark cycle and the timing of meals.
“In this sense, people who are obese and rodents fed high-fat diets tend to eat at night or in a disorganized way, which desynchronizes biological clocks. Several studies have found that restricting eating times to a few hours within the day (or within the night in rodents) resynchronizes biological clocks. This is important, since several metabolic improvements can be due to the control of these genes (biological clocks) over enzymes important in metabolism”.
microbiota
Periods of intermittent or prolonged fasting increase lifespan
Furthermore, at the level of microbiota Some benefits can also be found, since important changes have been observed in the intestinal bacteria of people or rodents that are subjected to intermittent fasting:
“Apparently, the microbiota of people doing intermittent fasting is more ‘healthy’ and less inflammatory. In addition, this microbiota produces active substances that regulate the metabolism of the host. In this sense, in rodents it has been observed that the microbiota of those subjected to intermittent fasting produces substances that accelerate metabolism and promote energy expenditure.
The research of Dr. Cruz, who performs reproductive and metabolic alterations in his laboratory, aims to study the effects of intermittent fasting in obese rodents. With this objective, they feed the mice only within eight hours at night, during their active period, and they are left with 16 hours of fast (during the day). In the study they have evaluated weight, blood glucose and other markers after six weeks of intermittent fasting.
Among the results, Dr. Cruz announced that they have observed a decrease in weight, fasting glycemia shows better tolerance to glucose and also shows a less fatty liver.
“We are studying the reasons for these beneficial effects even though the animals continue to consume a high-fat diet (but restricted in times). Our hypothesis is that metabolites are produced, including ketone bodies, which have anti-inflammatory properties at the central and peripheral levels. A decrease in inflammation would be one of the causes of the improvement in metabolic parameters”.
But how feasible is intermittent fasting as a therapy? Gonzalo Cruz states that, like all therapies, there is great variability in the individual response of those who do intermittent fasting.
“The greatest weakness of clinical studies is that despite the fact that they start with a large number of patients, very few manage to maintain intermittent fasting for the entire period evaluated. This emphasizes that there are people more in tune with this eating pattern and others who are not.»
«Although intermittent fasting does not present health risks, as prolonged fasting does, it can be associated with some adverse effects such as headache -especially the first few days-, dehydration, nutritional deficiencies and can be potentially dangerous in people with eating disorders.
«It is a priority that those who do not have knowledge of the subject seek advice from professionals, such as nutritionists, nutritionists or nutritionists, who help maintain a balance of the macro and micronutrients necessary to avoid losing muscle mass or having other alterations»recommends.