The risks and benefits of intermittent fasting, the fad diet that sparks debate among experts

Intermittent fasting is gaining more and more followers as a power resource to lose weight. However, for years this type of diet has generated an intense academic debate among nutrition experts, with strong detractors and defenders.

This diet proposes eating food during a short period of time and fasting for 16 to 18 hours a dayand postulates that this time restriction can trigger a metabolic change in the body and thus promote weight loss.

For many long-time nutrition experts, intermittent fasting falls under a long line of fad diets, formulas that are extended by times and that are promoted as effective but that sooner or later stop being used and are replaced by other eating plans. For this group of specialists, the keys to weight loss lie in the Healthy habits: take care of the size of the portions, choose foods with low fat and sugar content in each dish and the regular practice of physical activity.

The renowned doctor alberto cormillot is forceful: “The only thing that puts off intermittent fasting is the next meal”. The obesity specialist who has spent decades promoting healthy eating among Argentines considers that this type of diet is a modern way of what has always been known as “skip meals”.

“It simply doesn’t work because when people go to fast or half a day they eat a preventive meal, that is, they eat less before and then eat more to make up for everything they didn’t eat. In addition, the convenience of eating distributed during the day, at least four times, has been proven from a scientific point of view, ”said Cormillot in Infobae last week.

The expert said that many nutritionists recommended the time restriction regimen in the 1970s, but it was stopped in the 1980s due to its low effectiveness in the majority of patients: “At the first obesity congress held in London in 1974, I presented a paper on the application of this practice, but after 1977 or 1978 I stopped recommending it”.

Along the same lines, a scientific study published two weeks ago in the journal Journal of the American Heart Association indicated that restricting the time range in which you eat does not promote weight loss. The research followed 547 people and determined that the time between the participants’ first and last meal in relation to the time they got up or went to sleep did not influence their weight.

What did matter was the serving sizes of the participants: people who ate large or medium servings were more likely to gain weight, while those who ate less were more likely to lose weight.

Krista Varady, a nutrition researcher studying intermittent fasting at the University of Illinois, Chicagowas consulted by the magazine Time on the results of the study published in the Journal of the American Heart Associationand although he expressed that eating at a certain time does not produce magical effects, that does not mean that it is a completely useless concept.

The main reason not to demonize this method is that for some patients this type of eating plan may be easier to sustain than other diets that require counting calories, the scientist said.

Another American expert, Dr. Nisa Maruthur, an associate professor at the Faculty of Medicine of the Johns Hopkins Universitywho was not involved in this latest study but is involved in a broader initiative at the think tank to examine meal timing, said that while eating at a particular time is not in itself beneficial, she recommends eating at a certain time if it helps a particular person to eat more healthily.

“If your calories are the same regardless of when you eat them, there is no impact on weight. Nevertheless, setting time limits can help”, he indicated. For the expert, “if a person decides that they are only going to eat between 10 in the morning and 4 in the afternoon, the truth is that they may eat fewer calories, simply because of the number of meals that fit in that time.” .

For her part, the nutritionist Romina Pereiro, explained in Infobae that the scientific evidence still needs to be deepened to determine its risks or benefits conclusively. “We still don’t have meta-analyses or systematic reviews which are the best quality studies in research”, he told this medium.

However, the specialist remarked that “when proposing a pattern different from the one we are used to, the first thing people manifest are attacks of hunger and irritability with an emotional and behavioral impact. This happens because when they restrict food a lot, it is difficult to sustain it over time without generating the opposite effect: greater lack of control, disinhibition of impulses and negative emotions. And in certain people, You run the risk of developing an eating disorder..

Pereiro postulates that changes in habits are what make it possible to lose weight and sustain it over time. In simple words, obesity and being overweight are not disorders that are cured by stopping eating for more or less time.

“Obesity needs a comprehensive treatment that includes food education, physical activitythe management of emotions and that also contemplates the pleasure that it causes us to enjoy the foods that we like the most. It is not about suffering and starving. Hunger is a serious social problem, not a therapeutic measure to lose weight,” concluded Pereiro.

There are different types of fasting -dry, 12, 14, 16 or 24 hours-, but the one that is most talked about, because several famous people practice it, is 8/16. This plan consists of 16 hours of fasting and eight hours of eating, which must be healthy and balanced.

Nutrition specialist Tim Spector, a professor of genetic epidemiology at the King’s College of London and author of the books Eat to Live: The New Science of Eating Well Y The diet mythis a benchmark for the benefits of time-restricted eating in comprehensive health.

When a person spends a long time without consuming any food (no protein, no glucose, no carbohydrates, no fat) insulin levels begin to decrease, which would somehow favor organic and metabolic processes of detoxification and cell repair, according to the defenders of this type of plans to lose weight.

Therefore, instead of focusing on calorie counting to lose weight, the British specialist posits following a diet based mainly on plants and focusing on eating quality whole foods made with unprocessed “original ingredients”.

As recommended, dieters should eat foods in their “pure form,” such as nuts, seeds, fruits and vegetables. In an interview with Daily MailProfessor Spector said those looking to lose weight should avoid ultra-processed foods, try eat with time restrictions and try to eat 30 different plants per week.

“Fasting for 14 hours a day and eating breakfast later, but eating the same amount, is easier to achieve in the long run. It works because the microbes in our gut have a circadian rhythm like us and they need a rest period”, affirmed the British expert.

While the debates are going on around which are the best strategies to lose weight, specialists from the Southern Medical University in Guangzhou in China confirmed, after an investigation that was published in The New England Journal of Medicine (NJEM), that the method known as intermittent fasting does not have significant benefits compared to simple calorie counting in the task of controlling weight gain or reducing it.

The results obtained in this study after 12 months of diets assigned to the two work groups (one with a standard diet and others with time restriction for meal intake), mean weight loss was not significantly different. between the standard and the one with time restriction (8.0 kg vs. 6.3 kg). Furthermore, no significant differences were observed between the groups in body fat, lean mass, blood pressure, lipid profile, or insulin metabolism.

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