Intermittent Fasting – Everything you need to know
Surely if now I wonder what is the correct way to eat to stay young and healthy I say it is to make 6 meals a day, a breakfast high in carbohydrates, avoid junk food, drink plenty of water and eat protein in each of meals, however …
What if I say that fasting has more benefits than just lifestyle that I appoint?
Probably you tell me that I will lose muscle mass, I will suffer fainting by low blood sugar or even will increase my body fat % to put my body in a state of “emergency” where everything you eat will be stored as fat.
However, as you will see then anything I just said happens during fasting and even surely you will be surprised to see just the opposite happens …
- 1 What is intermittent fasting?
- 2 Health Benefits of Intermittent Fasting
- 3 Is it wrong to spend so many hours without eating?
- 4 How intermittent fasting work?
- 5 Should we have breakfast?
- 6 Muscle mass is lost during intermittent fasting?
- 7 ADF protocol or Alternate Fasts
- 8 Intermittent fasting and Fat Loss
- 9 How intermittent fasting affects obese and lean people
- 9.1 study
- 9.2 Study results
- 9.3 Increased lipolysis
- 9.4 Protein balance
- 9.5 Study conclusions
- 10 How intermittent fasting affects athletes?
- 11 Intermittent fasting for Athletes
What is intermittent fasting?
Intermittent Fasting (Intermittent Fasting) is nothing to restrict the number of calories you eat over a period. There are two types of intermittent fasting :
- Where fasting eat the extra calories for 5 days and 2 days will restrict ourselves to a 600-800kcal.
- A daily fast which eat all the calories in a window 6-8h and the rest of the day only eat liquids.
I personally recommend fasting point 2, since the circadian rhythms remain more constant, it is easier to follow and can adjust for those who practice sports.
Health Benefits of Intermittent Fasting
Intermittent Fasting can be an excellent tool to delay symptoms over time
But to understand how fasting slows aging must play some physiology (quiet, you`ll see that anyone can understand). When performing meals every few hours the levels of IGF-1 (insulin growth factor) increases, this results in a cell multiplication and hence aging cells.
Besides being constantly multiplying the likelihood of mutations it is higher (remember that part of existing diseases such as colon cancer can occur through this mechanism).
Intermittent Fasting decreases expression of IGF-1 that the body getting into “repair” mode lengthening the life of the cells. This is of great importance since it has been seen that this process can even prevent breast cancer.
Another factor that is affected and delay aging power are the telomeres. Telomeres are the ends of chromosomes, which act as “biological clocks” cell, where I reached a number of multiplications cells die.
However, intermittent fasting not only prevents internal aging, but also external. As can be seen in the study “Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study” monkeys performing intermittent fasting had a much younger looking than those who performed a “normal” intake while having the same age (24 years).
Subject performing a normal diet versus performing intermittent fasting subject
Is it wrong to spend so many hours without eating?
This is one of the biggest fears that people and has made us to do meals every 3 hours. The reality is totally different, no need to eat food every 3-4 hours to maintain adequate supply to cells and to perform both physically and mentally.
In fact, we can be even 84h without eating our glucose levels are kept constant through the action of epinephrine (also called adrenaline).
Obviously at any time 84h diet we will be fasting, but can we get an idea that our bodies tolerate being without food for more than 5 hours without repercussions.
In fact fasting reserves are as follows:
- Glucose or H. C.: 300 gr. (4 cal / gr.) = 1200 Kcal. Last more than 24 hours.
- Fat : 10 to 11 kg. (9 cal / g.) = 100,000 Kcal. They last more than 40 days and there are still reservations dead subjects. It is the most important.
- Protein : 10.5 kg. (4 cal / gr.) = 45,000 Kcal. Just consumed.
On the issue of fatigue, not only is not impaired even if not improved. This was reflected in the study “Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from intake calorie” where plasma glucose decreased, decreased insulin resistance (remember that a good insulin sensitivity prevents diabetes and produces a cleaner gain muscle with less fat) and even improved stress resistance by preventing neuronal injury.
How intermittent fasting work?
Intermittent fasting improves fat uptake by tissues, so that the body uses fat as the primary fuel and generate glucose from glycerol and amino acids (gluconeogenesis). It is believed that the amount of glucose generated through this process in 24h fasting consists of about 35-40g (sufficient to maintain the supply to those cells like red blood cells which can not use other fuel source).
During fasting hours it produced a number of mechanisms that triggers a release of growth hormone by the hypothalamus. This growth hormone (GH) prevents glucose consumed by the cells, so the use of fat is even higher. Moreover alone it is lipolytic (degradation of fat stores) and protects degradation in proteins, so it is a hormone that maintains muscle mass.
Another hormone that is elevated during fasting is the TSH (Thyroid Stimulating Hormone) increasing our metabolism, and decreasing the use of insulin. This is of great importance since hypothyroid people can take advantage of this effect to combat their disease.
Should we have breakfast?
The first thing to understand is that when we wake up our levels of cortisol (also called hormone stress), are elevated, like other hormones, such as epinephrine (adrenaline) and growth hormone (HGH). Although there are many theories about this phenomenon, which seems most widespread and accepted is that these hormones are elevated because our ancestors as they were preparing the body to find food (hunters). Particularly, for me the most successful is posed by Martin Berkham, which go from a sleep state to a state of “alert” or “active” challenges the homeostasis (the process by which our body responds to change through modification of other parameters, to ensure a stable condition)
These high levels of cortisol to wake is called CAR (Cortisol Awakening Response) whose peak is at 30 minutes of waking. That our cortisol levels are high does not necessarily mean that we are losing muscle mass, it is only that we are catabolizing, or what is the same, we are degrading macromolecules for energy, so this may be glucose through glycogen or fatty acids from our fat stores.
Degradation of muscle tissue for energy through the protein does not occur just as the protein hardly contributes energy (gluconeogenesis) and also our levels of growth hormone prevent such degradation.
Graph in which is reflected the time that our cortisol levels are higher is at 08: 00-09: 00 AM
Cortisol levels as you wake up, the maximum is 30 minutes
Another thing to keep in mind is that our lifestyle can further increase these levels of cortisol. As can be seen in the study “Differences in cortisol awakening response on work days and weekends in women and men from the Whitehall II Cohort”, subjects had higher levels of cortisol in the days of work, unlike the weekends whose levels were lower.
Within socioeconomic status, those who were poor had higher levels of cortisol, so as reflected our everyday stress translates to higher levels of cortisol. This is very important because exposure to elevated levels of cortisol so can lead to chronic heart problems, memory loss, depression, anxiety and especially fat gain
Another important factor to consider and breakfast is insulin, which is associated with levels of CAR is of great importance in people with type 2 diabetes.
Just our insulin levels are higher in the morning due to two reasons:
- High levels of cortisol that lead to insulin resistance
- Increased secretion of incretins
We will focus on two point is very important. Incretins, for those who do not know, are a series of hormones secreted in the intestine in response to food.
There are two types of incretin mainly the GIP and GLP-1. As can be seen in the study Differential islet and incretin hormone responses in morning versus afternoon after standardized meal in healthy men, levels of incretins are higher early in the morning than in the afternoon, leading to higher levels of insulin and lower levels of blood glucose.
Comparison between morning and afternoon, as we can observe glucose levels and insulin levels are much higher in the morning, unlike the glucagon that is lower in the afternoon
As many of you know, when high levels of insulin are produced in a short time and subsequent depletion of blood glucose levels, a greater feeling of hunger it is results. Does this mean that breakfast is something wrong? NEVER! All I want to show is that skipping breakfast does not have drawbacks as many say, and that our current breakfast can be an important factor in overweight subjects or diabetes.
However, is there any experimental study comparing the most calories ingested in the morning or in the late evening? The answer is yes, this study is Weight Loss is Greater Consumption of Large Morning With Meals and Fat-Free Mass Is Preserved with Large Evening Meals in a Controlled Women on Weight Reduction Regimen.
In this study they were separated into two groups:
- A group A, where energy consumption was distributed: 35% breakfast, 35% lunch, dinner 15% and 15% in the afternoon snack,
- And another group pattern PM with 15% at breakfast, 15% at lunch, at dinner 35% and 35% in a snack at night.
Both diets had similarly the same macronutrients:
- 60% carbohydrates
- 18% protein
- 22% fat.
To obtain the weight was held at 07:00 am after emptying bladders and before breakfast, where after a few weeks the following result was obtained:
As noted, the weight loss was greater in those who consumed the most calories in the morning unlike those who did night (-3.90 kg against the -3.27 kg of the night). But when you look around the table we realize that muscle loss was 1.28 kg in which strong breakfasting unlike 250g who lost those doing a good dinner.
This translates to a loss of body fat percentage of 1.83%, 2.52% unlike the fat they lost those who ate most of their calories in the evening.
Muscle mass is lost during intermittent fasting?
One of the major goals both athletes and overweight people are to maintain muscle during a fat loss phase. In this goal, many use protocols such as eating every 2 hours, increase protein intake above 3g / body kg or even look for supplements that help reduce cortisol, however what extent muscle mass is lost when we reduce calories?
We must differentiate between the effects that occur in the short term given the long run. This is because certain protocols do not negatively influence when it comes to hours or days but if muscle loss may occur if maintained for a long time. One example is the fasting. As I mentioned in other articles, the fasting hours (less than 24h) does not cause muscle loss, since at that time the liver glycogen helps supply the requirements of glucose that may need our body, as can be to maintain blood glucose or erythrocytes (blood cells).
ADF protocol or Alternate Fasts
A protocol where we see this is the ADF (Alternative Day Fasting). In it, the calorie intake is 25% of what is usually consumed in this way, if you eat 2400kcal daily, that day would be consumed 600Kcal ADF. You`d think this protocol would result in significant muscle loss as calorie intake is very low and therefore the protein intake will be less than what is needed. However, the reality is quite different.
ADF accompanied by a high – fat diet helps lose fat without losing muscle mass
One example is the study where it was subjected to 32 obese ADF protocol for 8 weeks, where they were given one high fat diet (45% of total calories) or a diet low in fat (25% of total calories), called ADF-HF (High fat) and ADF-LF (low fat) respectively. The group followed the ADF protocol with a high – fat diet lost 1.2 kg more body fat than did a diet low in fat (5.4 vs 4.2 kg).
An important detail given that more than one will be waiting, is that none of the two diets was loss of muscle mass. This makes us rethink what really makes us lose our muscle and to what extent the calories have worded on this subject.
This was not the only case where this protocol was studied. In this they took 64 obese who were divided into 4 groups depending on the protocol:
- Group A: ADF + Exercise Protocol
- Group B: Exercise alone
- Group C: ADF Protocol
- Group D: Control (without diet or exercise)
The ADF protocol followed was based on a protocol in which 450Kcal consumed (25% of calories usually needed) days followed where the person had no limit calories (days ad lib). Curiously, something that is critical of intermittent fasting is that adherence to these diets is low, something that does not agree with the study where adherence was higher than 80%.
The result obtained was as follows:
As we can see, after 12 weeks, it was observed that the group that combined an alternate fasting accompanied by exercise lost 5 kg of fat, while the group without diet or training practically got the same fat percentage. One of the characteristics of intermittent fasting (and carbohydrate restriction) is improved insulin sensitivity, which translates to a rapid loss of abdominal fat level. This is consistent with what this study is observed, resulting in a sudden drop waist circumference.
Like the previous study, muscle mass loss was minimal, where only ADF + exercise was the only one to prevent loss of muscle mass.
Intermittent fasting and Fat Loss
Many athletes when they start a diet to lose fat, come from a phase of “volume”, which is usually high in carbohydrates (intake of about 4-5g carbohydrate / body / day kg). This makes glycogen stores are almost full and therefore the muscle of a “bloated” or “bulky” appearance. As we cut calories, these glycogen stores decrease and therefore the muscle loses volume, the main reason why many are a less muscular physique, even with a low percentage of fat (for people who are in Plean Peak Week).
However, it is true that when we are in low – calorie diet can lose muscle, especially when we restrict the intake of calories or protein for several days (as I said at the beginning, long – term effects).
So what is the factor that most affects negatively the long term?
When we train our muscle atrophies largely because they increase the oxidizing species (ROS) and decreased ability to capture nutrients such as glucose (insulin resistance) or amino acids, producing a cascade that lead to muscle loss.
It is assumed then that training is the best way to prevent muscle loss (America has just been discovered). When we perform physical exercise they are released myokines, substances that help protect muscle mass and inhibit the growth of our adipocytes (cells which store fat), is why people who train do not express related atrophy/ muscle loss genes such as MURF-1 or atrogin two ubiquitin leading to sarcopenia.
How intermittent fasting affects obese and lean people
Little is said of the effects that omitting nutrients to the body during a set time whether hours or days. What are the differences that exist between people with different percentage of fat when making prolonged fasting?
To do this, we will focus on the paper of Mosegaard Bak and colleagues, in which they studied how it affected the fasting in obese and lean people. In this study, 18 people (9 obese and 9 thin) between 20-35, no smoking, no medication and low physical activity, were subjected to two protocols:
- Protocol A: where would 12h without food, something that closely resembles the intermittent fasting practiced by many.
- Protocol B: where they would 72h (3 days) without eating.
Between the two protocols would have a separation of 21 days (washout) to avoid interference between the results obtained.
Higher levels of insulin and C-peptide
As expected, obese subjects had higher levels of insulin and C-peptide before the procedure, showing a picture of low-grade inflammation and a resistance to the hormone. Both parameters decreased with fasting.
Higher levels of glucagon in 72h
On the other hand, higher levels of glucagon was observed in fasting 72h. For those who do not know, glucagon hormone whose primary role is to “break” liver glycogen to release into the bloodstream and thus maintain blood glucose in a controlled range.
Greater amount of FFA in 12h
As for fasting 12h, higher levels of free fatty acids (FFA) were observed in both groups, which no surprise because when no carbohydrates are introduced for several hours, the body resorts to lipid metabolism to save glucose, in other words, the body saves glycogen for situations inevitable necessity.
Something I found really interesting study is that cortisol levels increased after 72h of fasting in lean subjects but were reduced in obese people. We could speculate the reasons for the disparate results occur, but in my opinion it may be because: to have a lower percentage of fat in lean people, is a major stress to the body, which is observed in competing with % undersize 10% fat, where we see a worse balance of nitrogen.
If we continue to see the studies, we see that the increase in lipolysis (the process by which the stored triglycerides in our body fat known as adipose tissue break) was higher in obese people, because they had more body fat and about However, they had a lower expression of regulators in this tissue.
Regarding the protein balance and the effect of fasting on muscle tissue, we appreciate a decrease in the degradation and protein synthesis also worse results were obtained markers as mTOR and other partners, so prolonged fasting produce a worse cell environment objectives as hypertrophy (increased muscle mass).
However, we must remember that the subjects were sedentary people, so we would sportsmen different results, which in my opinion, would be worse.
Pay attention to nutritional content
Intermittent fasting can be a useful tool for some people who find it more convenient to reduce their frequency of meals, either for convenience or satiety, preferring to make a few meals but more content as food is concerned. However, this can be a double-edged tool, since in many cases, increasing the volume of food satiety before finishing intake is achieved, so imperiled macronutrient intake, especially of proteins that are it was associated with improved body composition.
Need for nutrition education
On the other hand, in some groups, such as obese people, can be helpful in reducing some parameters, however, although it can give good results in the short term, does not ensure that they stay as long as the person only learns to reduce the content caloric and does not receive nutrition education that allows you to keep a healthy lifestyle.
How intermittent fasting affects athletes?
Fasting in athletes is one of the most touched points in the world of fitness and sport in general, as many athletes looking to train with low glycogen stores to improve metabolic flexibility or performance:
Fasting and Metabolic Flexibility
For those who do not know what metabolic flexibility, it may be summarized as the ability of the body to utilize both fatty acid and glucose efficiently, which enables higher performance to improve efficiency. What we see in people who perform fasting (the real, not to not consume food in 8h) is that the circadian rhythm varies, so cortisol levels are lower in the morning and higher coming when the night.
Intermittent fasting for Athletes
Performance – wise, it has been observed that athletes such as rugby players who performed Ramadan, there was a decrease in performance. However, one must understand that Ramadan also prevents fluid intake, so it could be due to dehydration.
Another point to consider in studies where the performance of athletes is measured during Ramadan is the dream because they need more time to catch him and duration is usually shorter. This lack of sleep leads to decreased synthesis of glycogen, lower levels of testosterone and cortisol levels higher, which translates to a worse recovery from training.
If we eliminate all these negative factors such as poor sleep or dehydration, not to drink water during the day and took training under fasting a more “natural” point we can get some data more evidence:
The first of them is a better sensitivity to glucose by glucose when fasting train.
Noting this graph, we see that the end of training (post test) the glucose sensitivity was higher in the fasting group (F). This is due largely to the receptors GLUT4 (glucose transporter muscle level) was higher in the fasting group (black bar). Important detail is that healthy volunteers underwent a diet rich in fats.
To summarize, we note that people who train fasting increase glucose uptake mechanism.
Regarding body composition in athletes, some studies lasting three weeks watched a group of subjects who trained cyclists fasting decreased their percentage of fat without affecting muscle mass or performance. However, I am almost certain that a decline in performance would be in this group of cyclists if they increased their intensity to 80-90% of VO2max (maximum oxygen) as it would not have enough glycogen to meet that requirement.
As for protein synthesis, there are many rumors that fasting training produces a lower protein synthesis leading to a worse use post-training protein. When people who train fasting against persons training after eating are compared, we observed higher levels of p70S6K, which is a protein that activates protein synthesis, or in other words the train fasting favors increased protein synthesis, which in my opinion it is mainly due to increased protein breakdown during training (remember that the body tends to homeostasis or changes to keep our body stable).
Fasting in athletes not a problem in practice low-moderate intensity and short duration, because these intensities input from ATP from mitochondrial energy production pathways is remarkable. However, we must stress that today there is no clear evidence that training on an empty stomach or bypass carbohydrate intake during hours before the test, improve performance.
As a personal opinion, I think in some cases I train Fasting, can be counterproductive, as evidence in environments of high humidity and high temperatures, resulting in increased body temperature, increased sweating and therefore more “requirement” glycogen as energy source thanks largely to catecholamines peak occurs.