Intermittent fasting: understand if it works in cases of obesity
Friday, April 17, 2020
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Eating less often throughout the day helps you lose weight. That phrase seems obvious, doesn't it? But unfortunately it is not that simple.
The so-called intermittent fasting , a practice in which one or more of a meal (s) of the day is omitted, leaving the practitioner for up to 24 hours without eating, has been gaining more and more followers in Brazil following the fever of the Paleolithic diet and also because some celebrities have publicly declared themselves enthusiastic about the method. However, it is necessary to be very careful when talking about the subject.
To this end, I will echo the position of the American Heart Association (AHA, acronym for American Heart Association ), published in February 2017 in Circulation magazine , about the relationship between intermittent fasting and obesity.
When analyzing this topic it is important not to stick to the issue of body weight. After all, when manipulating the number of meals on the day and time of the same, a series of metabolic effects can also be produced - beneficial or not - that need to be taken into account. Examples of this would be changes in blood glucose (blood sugar), cholesterol and hormonal parameters. That said, let's go to a summary of the main points of the AHA's position that concern intermittent fasting.
It is not new that the practice of fasting is used for the purpose of producing weight loss. This has been happening for a long time in so-called "spas". When staying at a spa, some patients undergo periods of fasting with a focus on weight loss.
In addition, in some religions, periodic fasting has been a common practice for centuries. In this sense, studies with people who declared themselves to be practicing intermittent fasting for religious reasons, found a lower risk of developing diabetes mellitus as well as cardiovascular disease. However, such studies are observational in nature, that is, of lower quality from a scientific point of view. Studies that do not allow establishing a causal relationship, only an association.
Such studies are unable to adjust the groups that were compared (patients who had intermittent fasting versus patients who did not) for factors such as: level of physical activity, age and smoking - known to be related to the risk of diabetes and cardiovascular disease. In addition, these studies only evaluated people who fasted once a month.
Some studies, such as the "Malmo Diet and Cancer Study", done with 1,355 men and 1,654 women, showed that, in men, the risk of obesity was 2.42 times higher in those who ate 3 meals or less a day compared to those who ate 6 or more meals a day. Strange, isn't it? Those who ate less often a day had a higher risk of obesity.
Did these individuals eat less often a day, but a higher calorie intake after all? This information cannot be obtained from these studies. Another question: why was this relationship only seen in men? Was there any influence of sex on this issue? We don't know either. This shows how much of this issue still has many edges to be trimmed. It shows how complicated the subject is. It sounds simple, but it is not.
Regarding intervention studies, that is, studies better designed than so-called observational studies, two types of intermittent fasting were analyzed:
With studies that have shown benefits while others have not, we can conclude that there are still flaws in the available evidence. Existing studies do not mostly present a control group, that is, a group of patients who have had the standard treatment. In addition, the maximum duration of these jobs was 52 weeks (about 1 year). What will happen after a longer observation period? Or again: what happens after five or even ten years of intermittent fasting? Would there be any harm in prolonging the practice of fasting?
Despite all the benefits described, we do not want this article to look like a stimulus for people to do intermittent fasting. We understand that diets that encourage extreme behaviors, which can hardly be maintained in the long term, as well as fads or even therapies disclosed as panacea, should be discouraged.
The conventional method remains a recommendation, that is, a balanced diet, prescribed by a nutritionist, associated with a regular exercise program guided by a physical education teacher. Always having the endocrinologist as the centralizer of health actions and head of the multidisciplinary team.
On the other hand, we believe that continuing to study this very interesting subject is of paramount importance. More studies, well designed and with long-term follow-up are very welcome, can help us to better understand the topic and to draw lessons that can be applied in the treatment of obesity.
The so-called intermittent fasting , a practice in which one or more of a meal (s) of the day is omitted, leaving the practitioner for up to 24 hours without eating, has been gaining more and more followers in Brazil following the fever of the Paleolithic diet and also because some celebrities have publicly declared themselves enthusiastic about the method. However, it is necessary to be very careful when talking about the subject.
To this end, I will echo the position of the American Heart Association (AHA, acronym for American Heart Association ), published in February 2017 in Circulation magazine , about the relationship between intermittent fasting and obesity.
When analyzing this topic it is important not to stick to the issue of body weight. After all, when manipulating the number of meals on the day and time of the same, a series of metabolic effects can also be produced - beneficial or not - that need to be taken into account. Examples of this would be changes in blood glucose (blood sugar), cholesterol and hormonal parameters. That said, let's go to a summary of the main points of the AHA's position that concern intermittent fasting.
Are there studies on the application of intermittent fasting for people with obesity?
It is not new that the practice of fasting is used for the purpose of producing weight loss. This has been happening for a long time in so-called "spas". When staying at a spa, some patients undergo periods of fasting with a focus on weight loss.
In addition, in some religions, periodic fasting has been a common practice for centuries. In this sense, studies with people who declared themselves to be practicing intermittent fasting for religious reasons, found a lower risk of developing diabetes mellitus as well as cardiovascular disease. However, such studies are observational in nature, that is, of lower quality from a scientific point of view. Studies that do not allow establishing a causal relationship, only an association.
Such studies are unable to adjust the groups that were compared (patients who had intermittent fasting versus patients who did not) for factors such as: level of physical activity, age and smoking - known to be related to the risk of diabetes and cardiovascular disease. In addition, these studies only evaluated people who fasted once a month.
Can the same benefit be seen in those who fast more often?
Some studies, such as the "Malmo Diet and Cancer Study", done with 1,355 men and 1,654 women, showed that, in men, the risk of obesity was 2.42 times higher in those who ate 3 meals or less a day compared to those who ate 6 or more meals a day. Strange, isn't it? Those who ate less often a day had a higher risk of obesity.
Did these individuals eat less often a day, but a higher calorie intake after all? This information cannot be obtained from these studies. Another question: why was this relationship only seen in men? Was there any influence of sex on this issue? We don't know either. This shows how much of this issue still has many edges to be trimmed. It shows how complicated the subject is. It sounds simple, but it is not.
Regarding intervention studies, that is, studies better designed than so-called observational studies, two types of intermittent fasting were analyzed:
- Fasting on alternate days : which consists of eating a maximum of 25% of your daily caloric needs in one day (on the day of "fasting") followed by a day on which you can eat at will for 24 hours
- Periodic fasting : characterized by fasting for 1 to 2 days a week while eating normally for the remaining 5 to 6 days a week.
Benefits of intermittent fasting
Other benefits verified with the practice of intermittent fasting were:- Consistent reduction in triglyceride levels, from 16 to 42%. The better the greater the weight loss obtained
- Decrease in systolic (maximum) and diastolic (minimum) blood pressure, ranging from 3 to 8% and 6 to 10% respectively. Benefit this verified only in the studies that reached a loss of at least 6% of the initial body weight
- Improvement of insulin resistance, that is, intermittent fasting was able to improve the action of insulin in the body of practitioners . On the other hand, it is noteworthy that there was no benefit in the levels of HDL cholesterol (the good cholesterol), and the results in terms of total cholesterol, LDL and blood glucose were very variable.
With studies that have shown benefits while others have not, we can conclude that there are still flaws in the available evidence. Existing studies do not mostly present a control group, that is, a group of patients who have had the standard treatment. In addition, the maximum duration of these jobs was 52 weeks (about 1 year). What will happen after a longer observation period? Or again: what happens after five or even ten years of intermittent fasting? Would there be any harm in prolonging the practice of fasting?
Despite all the benefits described, we do not want this article to look like a stimulus for people to do intermittent fasting. We understand that diets that encourage extreme behaviors, which can hardly be maintained in the long term, as well as fads or even therapies disclosed as panacea, should be discouraged.
The conventional method remains a recommendation, that is, a balanced diet, prescribed by a nutritionist, associated with a regular exercise program guided by a physical education teacher. Always having the endocrinologist as the centralizer of health actions and head of the multidisciplinary team.
On the other hand, we believe that continuing to study this very interesting subject is of paramount importance. More studies, well designed and with long-term follow-up are very welcome, can help us to better understand the topic and to draw lessons that can be applied in the treatment of obesity.
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