As anyone who seeks to lose weight knows, diets enter and out of fashion. The pineapple diet, which was launched by a Danish psychologist in 1970, has never taken off. Kelleogg’s no longer enhances the special K special diet, which exchanges two meals per day for a bowl of breakfast with this name. These days, do not hear much about eating according to the type of blood, getting rid of acidic foods or following a potato diet.
However, intermittent fasting had the extraordinary survival force for more than a decade – and has grown more popular in the past few years. Wipe1 I found that nearly one of every eight adults in the United States had tried it in 2023.
The sudden cause of the renovative fasting authorities
The permanent popularity of intermittent fasting has been fed through celebrity approvals, news coverage and an increasing number of books, including many researchers in this field. More than 100 clinical trials in the past decade indicate that it is an effective weight loss strategy. Weight loss generally comes with related health improvements, including low risk of heart disease and diabetes. What is less clear is whether there are distinct benefits that come from reducing eating to certain windows of time. Does it protect against neurological degenerative diseases such as Alzheimer’s disease, enhancing cognitive function, suppression of tumors, and even extending age? Or are there no benefits regardless of those related to calories reduction? What are the potential risks?
Neuroscientist Mark Matson at Johns Hopkins Medicine School in Baltimore, Maryland, and author of 2022 book Intermittent fasting revolutionHe was studying fasting for 30 years. He argues that, because old humans went for long periods without food like the fisherman’s university, we have evolved to take advantage of taking periods of eating. “We have been adapted to work very well, perhaps optimally, in a state of fasting,” he says.
Deep roots of fasting
Fasting is far from the new. The periodic abstinence of food has been practiced long ago in many religions. In the fifth century B.C.E.It was prescribed by the Greek doctor and the philosopher Hippocrates for a group of medical conditions.
The recent scientific interest in fasting has its roots in the questions raised by research on calorie restriction. Since the thirties of the twentieth century, studies have shown that placing rodents on low -calorie meals can increase their life. Suggested hypotheses to explain this effect include that the restriction of calories slows growth, reduces fat intake or reduces cellular damage caused by unstable free radicals.
But the observation made by researcher Ronald Hart in 1990, who was then studying aging, nutrition and health at the American National Center for E toxicity in Jefferson, Arkansas, highlighted an interesting possibility. Rods restricted in calories that feed once every day consumes all their food within a few hours. Perhaps the calorie -bound rodents have lived longer because they went again and again for 20 hours or so without eating.
In the wake of the meal directly, glucose cells of carbohydrates are used in food as fuel, either immediately or continuing storage in the liver and muscles such as glycogen. Once these sources are exhausted – in humans, usually after about 12 hours of the last meal – the body enters a steady condition during which the fat stored in the fatty tissue is converted into ketone bodies for use as a source of alternative energy.
“Intermittent fasting” generally indicates many diets that include frequent periods of calories with very low calories that range enough to stimulate the production of ketone bodies. The most common time is TRE, which includes consuming all foods in a window of 4 to 12 hours, usually without counting calories; Alternative fasting per day (ADF), where people refrain from either food every day or eat more than about 500 calories on that day; The diet 5: 2, which provides for 500 calories in two days a week (see “three forms of fasting”).
Some researchers say that the resulting transformation between energy sources, called metabolism, leads to the main adaptive stress responses, including increased DNA repair, collapse and recycling defective cell ingredients. These responses, as thinking, provide health benefits that exceed those resulting from low caloric consumption alone. Observed studies have suggested that some monastery religions who fast long enough to convert metabolism to see such health benefits, although these studies have many restrictions.
Get fast bees
It is difficult to perform controlled diet experiences. Food meals and people’s behaviors, along with their genetic inheritance and the health of the foundation, make many variables. Often, people are not committed to studying, and obtaining the participants to accurately track calories that is a well -known challenge.
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However, the weight of evidence indicates that intermittent fasting can help people lose weight. In 2022, for example, Courtney Peterson, who is looking at nutrition at Alabama University in Birmingham, informed her colleagues about the results of a trial that included 90 adults who also received advice to help them lose weight. I found that those who followed TRE for 6 days a week over 14 weeks lost 6.3 kg, compared to 4 kg lost by the participants who took more than 12 hours or more2. Peterson says that many people find a base around the date of eating and when they do not eat easier than calculating calories or eating more healthy. “We and others have found that TRE also makes people less hungry, so they tend to eat normally and lose weight,” says Peterson.
Also in 2022, a dietitian Krista Farady from the University of Illinois, Chicago, and her colleagues reviewed 22 random experiences looking at ADF and 5: 2 diet on body weight. The ADF and Diet Agreement produced 5: 2 weight loss 4-8 % after 8-12 weeks in those who suffer from obesity, while TRE helped people lose 3-4 % of body weight during the same period.3.
Varady has a long -term interest in fasting. Cover one copy of her book 2013 Every day in the diet It includes pizza, cakes and burgers to explain that those who do AdF do not need to cut unhealthy foods. In the book, Farady argues that restricting eating no more than 500 calories each day is a more effective way to lose weight than the number of traditional calories and overcoming fatty and sugary foods.
Although most researchers who study intermittent fasting agree that it can help people lose weight, they are divided if there are any benefits that go beyond those that come from just less intake. Michelle Harvey, a dietitian at Manchester University, UK, sought to address this question in cooperation with Matson in the 2010 experience. They found that women who suffer from weight gain who followed a diet for 5: 2 for a period4. Both groups had the same weekly calories and lost an average of about 6 kg. But the difference in insulin levels was small, and the researchers relied on the participants to track consumption by maintaining food diaries.
Intermittent fasting often appeals to people who prefer to restrict when, rather than what they eat.Credit: Roger Pamper/Islam
In a 2018 study, Peterson and her team carefully monitored the meals of men with stealing, who suffer from weight gain, and match their diets with energy consumption. Participants ate all of their food either within 6 hours before 3 pm a day, or more than 12 hours, for 5 weeks before switching to the other eating schedule. Although both systems are caused by a small weight loss during the study period, when men were in a more restricted diet, they have improved insulin sensitivity, low blood pressure and low oxidative stress, a form of molecular damage5.
“We have first shown that intermittent fasting has health benefits and effects that exceed the loss of weight in humans,” says Peterson. But the study was relatively small: only 12 people started the experiment, only 8, and they were all male and overweight.
In addition to the uncertainty is that other experiences have come to seem contradictory conclusions. Nissa Marothor, a doctor at the Johns Hopkins School of Medicine, and her colleagues, has requested 41 adults with pre -diabetes or diabetes to consume meals that are suitable for their energy needs, and eating either during a daily window of 10 hours or according to their normal table. After 12 weeks, there was a little difference between the two groups in the average change in weight, glucose regulation, blood pressure, waist circumference, or fat levels6. “The weight loss seen in previous studies on Tre was the result of eating fewer calories,” said Marothor, whose studies were published in 2024.
Peterson, the co -author of that study, indicates that the 10 -hour food window may be very long to achieve the results seen in the experiences of Luxor Tre windows.
Although Faradi believes that intermittent fasting can help people lose weight, she is still not convinced that they have effects independent of calorie restriction. “Based on the current human evidence, I do not think that there are any benefits of intermittent fasting that exceeds weight loss,” she says.
Mattson is equally sure: “There is a great evidence of the benefits of intermittent fasting that cannot be explained by a decrease in calories.”
Matson and others looked at animal research in their efforts to understand fasting physiology, and identify mechanisms that can support any additional health benefits.