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What you need to know before you try intermittent fasting



As you may already know, especially if you are someone tracking healthy eating and weight loss, Intermittent Fasting (IF) is a diet that requires cycling between mealtimes and fasting times. The idea is that by restricting food, you control the number of calories you consume and hopefully benefit from the hormonal and cellular benefits that fasting can bring, such as lowering your cholesterol to improve your heart health and ultimately help you live longer. These claims are based on studies that examined the effects of IF on different markers, but they do not tell the full story. As an epidemiologist studying the effects of fasting on longevity and health, I've spent much of my career trying to figure out how much IF can affect our health.

Let's start with what intermittent fasting is exactly and why researchers are studying the effects on our health.

Fasting for religious, social, cultural or political reasons is a practice that has been practiced for many thousands of years in a variety of societies and civilizations. Intermittent fasting, however, is a certain kind of caloric restriction, which basically means only eating for a while and then not eating for another time. There is no way to practice IF, but usually it is about limiting food intake in two ways ̵

1; cyclical fasting or limited food.

Cyclic fasting includes protocols such as the 5: 2 diet. Usually eat normally for five days and follow a fast for two days a week. Alternatively, you can fast every other day. Time-bound fasting only means limiting the hours you eat to a particular window, such as the time you eat. B. All your food for the day between 10 in the morning. and 6 P.M. and the other 16 hours fasting.

IF as a research topic developed mainly from animal and laboratory studies on calorie restriction, which began in the early 2000s. These animal studies have found that two primary biological mechanisms are involved in creating health benefits. One of them is that IF can induce ketosis (which you may know thanks to the 19459004 ketogenic diet ), where the body gets energy from stored fats instead of blood sugar (which is usually the first step in the body). until when it needs energy). The other mechanism, which has 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 diseases and increase longevity. Later, more about it, but the key point is that the science of IF is still very young.

What does science say?

In 2015, two cardiologist colleagues and I conducted a report on scientific publications about intermittent fasting. We found that clinical research studies of fasting with robust designs and high clinical evidence were available in very few cases. With this review, we wanted to find out where IF Science was in terms of clinically good or excellent research that had been done up to that point. When I say "good" research, I mean studies that have been so rigorously designed and conducted that their results can be used as a basis for changing or aligning health practices. Specifically, our goal was to find studies that were randomized clinical trials of fasting using a certain type of control group or studies where the research endpoint was a clinical outcome (such as a diagnosis of diabetes ). We found little that matched the high standard of clinical trial research that could be used to develop guidelines for using IF to improve health. (Since our review, only three more good quality tests have been published.)

If there is little scientific evidence on the benefits of IF for health, why are they? then? There are loads of enthusiastic claims throughout the internet? One thing to consider in the so-called proven benefits of IF is the kind of studies that showed such benefits. The hype about IF and many of its claims are mainly based on basic animal or laboratory research and pilot studies on humans. The basic studies are often very good, but they only tell us what kind of human studies we should do. Human studies – not animals – should serve as a guide to human health practices. What we know about IF today comes largely from animal and other laboratory studies. Human pilot studies (preliminary studies testing the feasibility of a larger study) have provided some valuable data showing that we should continue to conduct IF research, but as the papers and reports themselves say we need higher evidence levels to provide useable knowledge and change dietary guidelines. Let's take a look at what we know so far.

IF and Weight Loss

In some good human studies it has been shown that the weight is reduced to a similar extent as in a conventional calorie-reduced diet. However, this is not the case shown more effectively. One study – one of the above quality grades – stated that "fasting on another day did not induce superior adherence, weight loss, weight maintenance or cardioprotection compared to daily calorie restriction." (19459004) "Three (fasting) cycles reduced body weight, trunk and total body fat …" along with a host of other factors that are needed to be further explored in future clinical trials. IF therapies were quite intense in these and other studies: every other day almost every day for a whole day, once a month for five consecutive days and almost every two consecutive days a week. Participants found that these therapies are difficult to maintain.

Many intermittent advocates of fasting claim that IF further triggers fat loss by altering hormone levels, but experts say these hormone changes are not significant enough to cause weight loss. "There are hormonal changes with intermittent fasting, but none is so profound that it has any clinical significance," says Deena Adimoolam, a lecturer in endocrinology at the Icahn School of Medicine at Mount Sinai, told SELF. "Many intermittent fasting protocols, for example, speak of an increase in the growth hormone levels, which triggers the fat loss. Growth hormones can lead to an increase in muscle mass; To achieve this, however, significant amounts of growth hormone are required, and these values ​​are not achieved with intermittent fasting. "Again, further research on this topic is needed in order to draw clear conclusions.

But what happens in times After a long fast, the blood sugar and insulin levels drop dramatically. med. Caroline Apovian, director of the Center for Nutrition and Weight Management at the Boston Medical Center, told SELF. The body converts to glycogen – carbohydrates that are stored in the liver and in the muscles – as fuel. When no glycogen is available for energy, the body goes into ketosis and turns into fat. However, with intermittent fasting, ketosis tends to be short, if it occurs at all, due to the short time you fast (relative to the duration of ketosis) before you eat again. Although the actual time of onset and end of ketosis will vary from person to person, for most people it is unlikely that most IF protocols will lead to ketosis.

IF and Diabetes

IF has also been studied for effects on various body systems, including metabolic, cognitive, and cardiovascular benefits. A good study among diabetics showed that IF has been as effective as (but not better than) a conventional diet for weight loss in recent months in combating hemoglobin A1c, which is a marker of average blood sugar.

The study of IF as a management method for hemoglobin A1c in diabetics showed that IF is an option that can be used instead of other nutritional techniques used for blood sugar management. However, it is important to note that IF does not replace medications prescribed for the treatment of diabetes. The use of IF for the treatment of a chronic disease, such as diabetes, is a secondary prevention approach in which you try to prevent the aggravation or progression of the disease, and this should be done under the supervision of a physician.

IF and Heart Health

Here's where we plunge into the research that I and my colleagues have been studying for years. First, some background information: What interested me first for the study of the IF was a series of studies about 40 years ago at the University of Utah, which shows that the Most cancers in Utah die and heart disease was significantly lower than in the rest of the United States. This was attributed to the low smoking rate in Utah. The idea was supported by a UCLA study at about the same time, which reported that religiously observing members of the Church of Jesus Christ of Latter-day Saints in California had a longer life expectancy than other Californians with a longer life expectancy of more than seven years. In 1998, I attended an epidemiology course taught by a researcher from Utah. I could not find any academic research on IF at that time, but fasting (a regular and common practice in The Church of Jesus Christ of Latter-day Saints) was a potential heart-protection behavior that had not been scientifically studied.

In 2001 I started my PhD. Program in genetic epidemiology and continued to work at Intermountain Healthcare, where I worked since 1996. This position gave me the opportunity to do some medical research, and in 2002 I proposed the idea of ​​investigating whether a factor beyond smoking affects heart disease. The patients my cardiologists, colleagues, and I served with Data from Intermountain's electronic patient records (from the 1960s health data) actually confirmed that another factor besides smoking is important. This led to a prospective study in 2004 examining whether fasting (mainly for religious purposes) affected coronary artery disease. In this study, we asked people: "Do you regularly abstain from food and drink for long periods of time (H. Schnell)?"

The results of this 2008 study were profound. Among those routinely reporting on fasting, the risk of suffering from heart disease was significantly lower than among those who did not fast, even if many other factors and behaviors were considered. The risk of receiving diabetes diagnosis was also lower in Fasters, although this was not our primary hypothesis. To test whether the diabetes finding is valid, we conducted another study in 2012, which asked the same question about fasting, but primarily examined whether it was linked to diabetes. The risk of diabetes was noted among those who routinely fasted to be significantly lower. As we noted in the study, the lower risk of cardiovascular disease could be due to either fasting or fasting. For example, fasting may improve a person's self-control over appetite and desire, resulting in lower daily calorie intake. Caloric intake was not included in this study so calories or any other dietary factor (vitamins, nutrients, etc.) could explain the finding, but adjustments in the study for many other factors did not affect the results. In other words, more research is needed to learn more about the causal relationship between these findings and diet or nutritional discipline.

The average fasting participant in my studies in 2008 and 2012 had fasted one day almost daily for 45 years (his age), an average of 65 years). This indicated that some of the results we see from IF are due to IF being implemented as a long-term lifestyle, as opposed to a short-term solution to, for example, losing weight. It had taken many decades for the benefits of coronary and diabetes to become apparent. That was not a bad thing. Since coronary disease, diabetes, dementia, and other chronic non-infectious diseases usually develop only after decades, a low level of chronic protection of an IF lifestyle over that time period (and we assume that is the case) could prevent These diseases develop and progress silently.

Other Possible Benefits of IF

With the exception of weight loss, research was limited to the effects of IF on humans on scientific tests, the secondary effects on weight loss or the evaluation of IF without a parallel control group, which allow researchers would examine and isolate any variables that could lead to a particular outcome. Possible benefits of IF from these limited pilot studies include improved blood pressure, cholesterol levels, markers of cognition / dementia, insulin, mood and quality of life, and IF may reduce depression and insulin resistance. There may also be other benefits. No study has examined these results as a primary issue or hypothesis, so it is unclear whether the non-weight-loss effects in pilot studies are real and reproducible or are random events.

Why is not there anymore? Studies on IF, if their potential for influencing our health appears promising?

Although weight loss is an important area of ​​research, it is not what I consider to be the most interesting or potentially most effective result of IF as someone who studies intermittent fasting and cardiovascular disease. Preventing chronic illnesses, increasing life expectancy and improving the quality of health in old age seems to be a potential result that IF can achieve. IF may be able to offer benefits regardless of weight loss. I do not want the public or the scientific community to focus so much on the aspect of the Fad diet of IF that we are not exploring whether IF is a dietary intervention that could preserve and regenerate human health. Unfortunately, research on non-weight loss outcomes has not been studied as carefully as it should be for something that has provoked the social transition of IF. Weight loss is certainly easier to sell to grant financiers and the public, also because it can be seen and felt when it occurs. In addition, research into nutritional health effects is known to be difficult to accomplish, as all combinations of foods we can eat – or in the case of IF do not eat – and the challenge to measure and account for all of these combinations is not surprising that the hype may not correspond to the reality of IF.

However, it is often even more difficult to investigate whether the focus on the use of IF may change cardiovascular health outcomes, and not just the risk factors, as research would have done so in the long run and in a population that meets several cardiovascular health criteria (eg. Weight, blood pressure and cholesterol). Despite the risk factors, no one can feel when their cholesterol changes, and most people, for example, can not feel it when their blood pressure is high. But cholesterol and blood pressure in and of themselves are not of paramount importance to health. What interests us as health care providers and researchers is what happens when people who are considered overweight also have high cholesterol and / or high blood pressure. A higher proportion of people who meet this description will develop coronary disease, diabetes and other heart, lung and related diseases compared to those with normal risk factors (although it is important to note that not everyone with is higher Weight has or higher cholesterol or blood pressure develop these diseases). Unfortunately, a study of disease outcomes in people starting IF today takes decades and is very expensive, so the epidemiological evidence we currently have is probably the only outcome data for some time.

No matter what, it is important to remember extremely restrictive diets have a notoriously high failure rate and are generally not very sustainable.

The weight and health effects of a diet, including IF, does not matter if you do not stick to the nutritional protocol in the long term. "There is no single nutrition that is best for everyone," says Donald K. Layman, professor emeritus of food science and human nutrition at the University of Illinois, to SELF. "This is one strategy among many."

If you want to try IF, you should first talk to your doctor and make sure it's something that you think is healthy, both physically and mentally to attempt. You should also do this under the supervision of your doctor or a registered nutritionist. I would recommend anyone who suffers from a disturbed food history and does not try IF. The duration and frequency of the IF protocol you use and the duration of the treatment (several months versus many years) may vary depending on your current state of health. For example, it is unlikely that someone who is a younger adult and / or appears to be healthy and wants to lose weight or build a low life risk for a chronic condition needs an intense IF regimen. It is not known how IF affects the menstrual cycle. Therefore, it is important to keep track of how this affects you. Make any IF regime a sustainable lifestyle that you do not need to stop abruptly (usually when diet practice is difficult to keep this is an indication that it's too rigid or too severe) , [19659031] Considering that IF is one of the more extreme ways to eat and live, Adimoolam recommends that you talk to your doctor if you are curious about making sure he is physically and emotionally fit for you. If you're interested in losing weight, remember that dieting shows that weight loss diets tend to fail when deciding what to do. Instead, are looking for strategies that are not extreme, that do not require deprivation, and that take into account your mental health. .

The bottom line: IF is not a panacea and when it comes to weight loss, it's no better than standard diet for weight loss.

It is not for everyone and it is one of many preventative methods that can improve your health and longevity. Other methods include smoking, eating a healthy low-salt and low-cholesterol diet as well as exercising physical routine. These other methods of disease prevention have far more scientific evidence than IF. However, IF is proving to be a promising intervention in health care and can shift from alternative medicine to practical mainstream use if science and practice are used effectively. IF makes that transition, but we need additional research before we can make clinical statements that are safe to diet and individual behavior.

In other words, scientists and researchers should be much more responsive to the potential of IF than the average person who, as I mentioned above, can do better accessible (and more proven) healthy behaviors.

Additional coverage by K. Aleisha Fetters

Dr. Benjamin D. Horne, M.STAT, MPH, FAHA, FACC, is Director of Cardiovascular and Genetic Epidemiology at the Intermountain Heart Institute, Salt Lake City, UT, and has a position in the Department of Biomedical Informatics at the University of Utah. Dr. Horne pursues research interests in the areas 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-making tools that maximize both scientific validity and clinical feasibility for the personalization of medical care. They also include improving the health of large populations by detecting the effects on human health through intermittent fasting, assessing genetic risk factors for associations with heart disease outcomes and examining the effects of short-term increases in air pollution on health.


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