What you need to know before trying intermittent fasting

As you may already know, especially if you follow someone Healthy eating and trends in weight loss, intermittent fasting (SI) is a diet that calls for cycling between meal and fast periods. The idea is that by limiting the time you eat, you control the number of Calories you consume and, hopefully, enjoy the hormonal and cellular benefits that fasting can bring, such as reducing your cholesterol, improving heart health, and ultimately helping you live longer. These claims are based on studies that have examined the effects of IF on different markers, but they do not tell the whole story. As an epidemiologist studying the effects of fasting on longevity and health, I have spent a good part of my career trying to determine how much the IF could affect our health.

Let's start at the beginning by examining exactly what is intermittent fasting and why researchers are studying its effects on our health.

Fasting for religious, social, cultural or political reasons is a practice observed for thousands of years in various societies and civilizations. Intermittent fasting, however, is a specific type of caloric restriction that basically means simply eating for a period of time and not eating for another period. There is no single way to practice IS, but it usually involves limiting food intake in two ways: cyclic one-day fasting or restricted feeding.

Cyclic fasting includes protocols such as the 5: 2 diet, in which you normally eat for five days and fast for two days a week, and fasting every other day, where you fast every other day. A time-limited fast simply means limiting the hours of the day when you eat at a particular window, as if you were eating your whole day between 10 am. and 6 P.M. and fast the other 16 hours.

As a research topic, the IF developed mainly in the early 2000s from animal and laboratory analyzes on caloric restriction. In these animal studies, two main biological mechanisms have been involved in creating health benefits for the IF. The first is that IF can induce ketosis (which you may know from the ketogenic diet), where the body draws its energy from stored fat instead of blood sugar (which is usually the first thing to do when the body needs energy). The other mechanism, which has again been studied in animal research, is that cells and tissues can enter a phase of rest, renewal and rejuvenation. This could reduce the risk of chronic illness and increase longevity. More on these later, but the bottom line is that the science on IF is still very young.

So what does science say?

In 2015, two fellow cardiologists and I led a review of scientific publications on intermittent fasting. We found that clinical research studies on fasting with robust designs and high levels of clinical evidence were rare. With this review, we wanted to determine where the IS science was in terms of clinically good or excellent research that had been done so far. When I say "good" research, I mean studies that have been designed and conducted in a sufficiently rigorous way that their results can be used as a basis for modifying or guiding health practices. In particular, our goal was to find studies that were randomized fasting clinical trials using a particular type of control group, or studies in which the search criterion was a clinical outcome (such as a diagnosis of diabetes). We have found few solutions that meet the high standards of clinical trial research that can be used to develop guidelines on the use of IF to improve health. (Since our examination, only three more well–quality the tests were published.)

If the scientific knowledge of the benefits of the FI for health are unscientific, why are there tons of enthusiastic claims on the Internet? It is important to keep in mind that when looking at the so-called proven benefits of FI, this is the type of study showing these benefits. The hype around the IF, as well as many of the claims associated with it, is mainly based on basic research on animals or in labs and pilot studies on humans. The basic studies are often very good, but they tell us only what types of human studies we should conduct. Studies on humans, not animals, should be used to guide human health practices. The vast majority of what we know about today's IF comes from animal research and other laboratories. The pilot human studies (which are preliminary studies in which the feasibility of a larger scale study is tested) have provided valuable data showing that we should continue to conduct research on the IS, but like documents and reports himself State, we need more evidence to provide actionable knowledge and change nutrition guidelines. Let's see what we know so far.

SI and weight loss

It has been shown in some quality studies on humans that IF reduces weight in the same way as a traditional diet based on caloric restriction, but its effectiveness has not been demonstrated. A study– one of the quality problems I've mentioned above – revealed that "alternating fasting did not produce a higher adherence, weight loss, weight maintenance or cardioprotection than those of A daily caloric restriction ". And the other (also one of those of good quality) I mentioned) concluded that "Three cycles (fasting) reduce weight, trunk and total body fat …", as well as many other factors that need to be explored further in future clinical trials. The FI regimens in these and other studies were quite intense: fast one full day every other day, fasting for five consecutive days once a month and fasting on two non-consecutive days per week. Participants found these patterns difficult to maintain.

Many intermittent fasting advocates claim that the IF also triggers fat loss by altering hormone levels, but experts say that these hormonal changes are not important enough to cause weight loss. "There are hormonal changes with intermittent fasting, but none is so profound as to have any clinical significance," says Deena Adimoolam, MD, assistant professor of endocrinology at Icahn Medical School on Mount Sinai. "For example, many intermittent fasting protocols speak of an increase in growth hormone levels resulting in fat loss. Growth hormone can lead to an increase in lean body mass; however, significant amounts of growth hormone are needed to achieve this goal, and these levels are not reached with intermittent fasting. Again, we need further research on this topic to draw solid conclusions.

However, during periods of prolonged fasting, blood glucose and insulin levels drop dramatically, says Caroline Apovian, MD, director of Boston Medical Center's Center for Nutrition and Weight Management. The body turns to glycogen (carbohydrates stored in the liver and muscles) to make it the fuel. When there is no glycogen available for energy, the body goes into ketosis and turns into fat for energy. However, with intermittent fasting, ketosis tends to be brief, even if it occurs because of the short time that you fast (compared to the time it takes to start) before eating again. Although the actual timing of the beginning and end of ketosis varies from one person to another, it is unlikely that most IF protocols will cause ketosis in most people.

SI and diabetes

IF was also examined to determine its effects on various body systems, including its metabolic, cognitive, and cardiovascular benefits. A good study in people with diabetes have shown that IF was as effective as a conventional weight loss regimen (but not better) at controlling hemoglobin A1c, a marker of average blood glucose over the past few years. month.

The IF study as a management technique for hemoglobin A1c in people with diagnosed diabetes has shown that IF is an option likely to replace others. diet techniques used for the management of blood sugar. But it is important to note that the IF does not replace the medications prescribed to treat or manage diabetes. The use of IF to treat a chronic disease such as diabetes is a secondary prevention approach in which you try to avoid worsening or progression of the disease and should be done under the supervision of a doctor.

SI and heart health

This is where we come to the research my colleagues and I have been studying for years. First, a bit of background: what interested me first to study SI was a series of studies about 40 years ago, from the University of Utah, which showed that death rates from most cancers and heart disease were significantly lower than those of the rest of the United States. This is attributable to the low rate of smoking in Utah. The idea was reinforced by a UCLA study At about the same time, members of the Church of Jesus Christ of Latter-day Saints practicing religion had a longer life span than other Californians, with a longer life expectancy of more than seven years . In 1998, I attended an epidemiology course taught by one of Utah's researchers. At that time, I did not find any academic research on SI, but fasting (a regular and routine practice in The Church of Jesus Christ of Latter-day Saints) stood out as a potential heart-guarding behavior that has not yet been scientifically investigated.

In 2001, I started my PhD program in Genetic Epidemiology and also continued working at Intermountain Healthcare, where I had been working since 1996. This position gave me the opportunity to do some medical research. In 2002, I proposed to investigate whether factors other than smoking had an impact on heart disease. the patients my fellow cardiologists and I served. Using the rich data available in Intermountain electronic medical records (which included health data from the 1960s), we have indeed confirmed that another factor other than smoking was involved. This led to a prospective study in 2004 to determine whether fasting (mainly for religious purposes) affected coronary heart disease. In this study, we asked people, "Do you regularly refrain from drinking and eating (that is, quickly) for long periods of time?"

the results of this 2008 study were profound. Among those who reported fasting regularly, the risk of being diagnosed with coronary heart disease was considerably lower than among those who did not fast, even considering many other factors and behaviors. The risk of being diagnosed with diabetes was also lower among the fasters, although this was not our main hypothesis. To check if the discovery of diabetes was valid, we performed another study in 2012, we asked the same question about fasting, but we mainly asked if it was associated with diabetes. The risk of diabetes was found to be considerably lower in those who fasted regularly. As we noted in the study, the lower risk of cardiovascular disease could be due to fasting or behavior resulting from fasting. For example, fasting may improve the control of a person's appetite and desires, which may result in a reduction in daily caloric intake. And this study did not examine caloric intake, so calories or other dietary factor (vitamins, nutrients, etc.) might explain the results, but the adjustments made to the study for many other factors did not affect the results. In other words, more research is needed to find out more about the causal link between these findings and diet or dietary discipline.

The average fasting participant in my studies in 2008 and 2012 had fasted about a day a month for 45 years (their average age was 65). This indicates that some of the results we see from the FI are due to the fact that FI has been adopted as a long-term lifestyle, as opposed to a short-term solution for, for example, weight loss. . It took decades for coronary and diabetic benefits to become evident. It was not a bad thing. Since coronary heart disease, diabetes, dementia, and other chronic non-infectious diseases usually take decades to develop, having a little chronic protection through an IF lifestyle during this period could ( and we expect this to prevent the development and silent progression of these diseases.

Other possible benefits of FI

With the exception of weight loss, research on the effects of IF on humans is limited to scientific tests on the side effects of weight loss or weight loss. FI evaluation without a parallel control group, which would allow researchers to monitor and isolate any variables that might be changed. bringing a particular result. Some of the potential benefits of FI resulting from these limited pilot studies include improved blood pressure, cholesterol levels, markers of cognition / dementia, insulin, mood and quality of life, and that IF can reduce depression and insulin resistance. Other benefits may also exist. However, as no study has examined these results as a main question or hypothesis, it is not clear whether the weight loss effects in the pilot studies are real and reproducible, or are fortuitous events.

Why are there no other studies on IF when its potential to affect our health looks promising?

Weight loss, while an important area of ​​research, is not what I consider, as a specialist in intermittent fasting and cardiovascular disease, the most interesting or potentially most impactful outcome of IF. Preventing chronic diseases, increasing longevity, and improving the quality of health at a later age appear to be potential outcomes that the IF might be able to deliver. If may be able to provide benefits regardless of weight loss. I do not want the public or the scientific community to focus so much on the fledged FI regime that we can not determine if the IF is a food intervention that could preserve and regenerate human health. Unfortunately, research on results other than those related to weight loss have not been examined as thoroughly as they should for something that has created the social buzz that has occurred at IF. Weight loss is certainly easier to sell to funders and the public, in part because it can be seen and felt as it occurs. In addition, it is notoriously difficult to conduct research on nutritional influences on health because of all the combinations of foods we can eat – or, in the case of AI, not to eat – and the challenge of measuring and counting all these combinations. it's no wonder that the hype does not match the reality of what the IF can do.

But it is often even more difficult to study whether the importance given to IF can alter the outcomes for cardiovascular health and not just the risk factors, as the research should be conducted in the very long term and in a population responding to several criteria for cardiovascular health (for example: weight, blood pressure and cholesterol). Even with risk factors, no one can feel when their cholesterol levels change and most people can not feel it when their blood pressure is high, for example. But cholesterol and blood pressure alone are not important for health. As health care providers and researchers, what really matters to us is what usually happens when people who are classified as overweight also have high cholesterol and / or high blood pressure. A higher proportion of people with this description develop coronary artery disease, diabetes and other heart, lung and related diseases compared to people with normal levels of these risk factors (although it is important to note that everyone does not have higher weight or higher cholesterol or blood pressure will develop these diseases). Unfortunately, a study of the consequences of the disease in people starting with the FI today will take decades and will be very expensive, so the epidemiological evidence we have is probably the only data on the results for some time .

Be that as it may, it is important to remember that extremely restrictive diets have a notoriously high failure rate and are generally not very durable.

None of the effects on weight or health of a diet, including the SI, does not matter if you can not stick to the long-term diet protocol. "There is no single diet for everyone," says Donald K. Layman, Professor Emeritus of Food Science and Human Nutrition at the University of Illinois at SELF. "It's a strategy among so many others."

If you want to try IF, the first thing to do is talk to your doctor and make sure it's something that he thinks would be healthy, both physically and psychologically, that you should try. You should also do so under the supervision of your doctor or dietician. I would recommend anyone with a history of eating disorder not to try the SI. The duration and frequency of the IF protocol you are trying to use and the duration of use (a few months rather than several years) may vary depending on your current health status. For example, a person who is a younger and / or apparently healthy adult who wishes to lose weight or establish a low risk of chronic illness during his / her lifetime will probably not need treatment Intensive for the FI. It is not known how FIs affect the menstrual cycle. It is therefore important to monitor how this affects you. You need to make any IF diet a sustainable lifestyle that you will not need to stop abruptly (usually when a dietary practice seems to difficult to stick tothis is an indication that it is too rigid or normative).

Whereas IF is one of the most extreme ways to eat and live, if you are interested, Adimoolam recommends talking to your doctor to make sure your physical condition is right for you, physically and emotionally. If weight loss interests you, keep in mind that when trying to decide how to do it, research has shown that dieting tends to fail. Instead of, look for strategies that are not extreme, do not require deprivation, and take into account your mental health.

The bottom line: SI is not a panacea, and when it comes to losing weight, it's not better than standard weight loss diets.

This is not for everyone and is one of many preventative methods that can improve your health and longevity. Other the methods prohibit smoking, follow a healthy diet, low in salt and cholesterol, and do routine physical activity. These other methods of disease prevention rely much more on human scientific evidence than on IF. That said, the FI is very promising as an intervention in the field of health and can move from alternative medicine to traditional use if science and practice are carried out wisely. If the transition is underway, but we need additional research before we can create clinical statements that confidently inform nutritional guidelines and individual behavior.

In other words, scientists and researchers should be much more enthusiastic about the potential of the FI than the average person who, as I mentioned above, can adopt healthy behaviors. more accessible (and more tested).

Additional report by K. Aleisha Fetters

Benjamin D. Horne, Ph.D., M.STAT., MPH, FAHA, FACC, is Director of Cardiovascular and Genetic Epidemiology at the Intermountain Heart Institute in Salt Lake City, USA. UT, and holds an adjunct position at the Department of Biomedical Informatics at the University of Utah. Dr. Horne is pursuing research in the field of population health and precision medicine through the unique resources and features of Intermountain and its service area. These include the development and implementation of clinical decision tools that maximize both the scientific validity and the clinical feasibility of personalizing medical care. They also include improving the health of large populations by discovering the effects of intermittent fasting on human health, assessing genetic risk factors for determining associations with the consequences of heart disease, and studying the influence of the disease. short-term rise in air pollution on health.