What Is Intermitted Fasting?
Intermittent fasting describes an eating plan in which you switch between periods of eating normally but generally healthily to periods of fasting. It is not a diet in the sense that it does not restrict the type of food that you eat. This is not a new concept, with many hunter-gatherers missing out on meals if they could not catch their next meal. Due to this, evolution has enabled us to go without food for longer periods of time.
Additionally, intermittent fasting is also used by many different religions, including Islam, Buddhism, Christianity and Judaism. Recently, it has been adopted by many different health and exercise gurus for its benefits on the body.
In recent years, our lifestyles have changed. We are no longer working outside or playing as many sports. Instead, we are accessing entertainment from the palm of our hands, streaming content and staying indoors more. This has led to a change in our diets, with more people increasing their calorie intact and reducing their output due to a lack of exercise. This has led to an increase in levels of diabetes, obesity and heart disease, amongst others. Intermittent fasting may help combat this and improve health.
There are many different ways of intermittent fasting, including the 16 hours fast or fasting for two whole days every week but more on this later.
How Does Intermittent Fasting Work
There are many different types of intermittent fasting; however, they all focus on scheduling regular periods throughout the day to eat and periods to fast. Matterson describes how for the hours without food, the body works through its sugar stores and then turns to burning fat in a process known as metabolic switching. This can lead to weight loss over time as calorie intake tends to be reduced and fat is being used up. Studies have also shown that intermittent fasting can increase norepinephrine in the body which is a hormone that increases the metabolic system leading to increased calorie burning. It can also reduce insulin levels which manage your blood sugar which can help promote weight loss.
To put it simply, the more food we eat, the more fat and sugar we store in our bodies. Glucose or guar is stored as glycogen in the liver and muscle, while excess carbohydrates are stored as fat after a process of de-novo lipogenesis. This fat is then stored throughout the body.
When we do not eat, however, due to periods of intermittent fasting, this process reverses, allowing the body to burn the fat stored throughout the body and limiting the levels of glucose. Therefore, your body is constantly in one of two states, the fed state where it is storing energy or the fasted state, which it is burning through its energy reserves. If the time spent in fat burning and fat creating states is balanced, then weight levels will stay constant.
The Benefits of Intermittent Fasting
Intermittent Fasting has a number of documented benefits, tested by expert scientists. Take a look below at the extensive list.
Intermittent fasting leads to your body using up the glucose that it prefers to use for energy to fuel your body. After the glucose is used up, the body then begins to burn fat and use this for energy – which is known as a process called ketosis. One study found that over a 3 to 12 week period, intermittent fasters lost around 8% of their body weight and 16% of their body fat.
Reduction in Cellular Waste
The cells in your body can, on occasion, become damaged over time and collect waste. This can then inhibit the functioning of the cells, meaning that your body becomes sluggish and does not work properly. Studies have shown that intermittent fasting can lead to autophagy, where the body removes this waste and begins to work more efficiently.
Promotes Healthy Aging
Intermittent fasting can protect insulin sensitivity and the cardiovascular system leading to better ageing. It can reduce stress levels, making fasters feel more calm. Over longer periods of time, intermittent fasting has been found to increase the immune system, protecting against disease and increasing life expectancy. One study on rats found that, on average, rats that fasted lived up to 83% longer than rats that were not, however, more research needs to be done in this area for accurate human results.
Recent studies on intermittent fasting have also shown that it can reduce inflammation markers within the body. This can, in turn, have a positive impact on many chronic diseases that are impacted by higher inflammation levels.
Better Heart Health
In addition to weight and fat loss, one of the main benefits of intermittent fasting is increased heart health. This is because the process can reduce the levels of bad cholesterol in the body as well as triglycerides in the blood, inflammation levels, sugar levels and insulin resistance. All of these factors are huge risk factors for heart disease. Intermittent fasting allows the body to use fat for fuel as it has depleted the glucose reserves in the body. This is beneficial as the fat is a cleaner energy source that can lower the levels of triglyceride and improve blood pressure around the body – which can again, in turn, improve heart health and circulation.
Positive Impact on Many Cancers
Intermittent fasting can have a positive impact on cancer patients as well as reducing the risks of cancer in the first place. Studies on animals have shown that it may prevent cancer from occurring in the first place, while it also increases lymphocytes in the body. Lymphocytes are sent by the body’s immune system to deliberately infiltrate and attack cancer tumors, destroying the cells.
Cancer patients also reported that intermittent fasting before treatments for cancer, such as chemotherapy, led to decreased side effects from the treatment. Another study supported this by concluding that cancer patients who used the alternate day fasting method before undergoing their chemotherapy sessions experienced fewer deaths and increased cure rates.
Improved Brain Health
One of the main hormones that work within the brain is BDNF which helps the brain function correctly. Intermittent fasting has been found to increase levels of this hormone and also aids the growth and creation of new nerve cells. Studies have also shown that it can improve brain diseases such as Alzheimer’s.
Reduction in Hunger Pangs
Intermittent fasting has an impact on many different hormones in the body. Leptin helps to decrease your feelings of hunger, while ghrelin is reduced, which makes you feel less hungry. The fasting can also improve dopamine levels in the brain, which can lead to a feeling of happiness and content. For more info in this subject see our article with information on how to curb hunger pangs while intermittent fasting.
Improvement in Gut Health
Chronic conditions that impact guy health, such as Irritable Bowel Syndrome and Crohn’s disease, are frequently worsened by inflammation within the body and by overeating. Intermittent fasting can reduce calorie intake and lower inflammation markers leading to those with gut conditions noticing positive improvements in their symptoms.
Reduction in Symptoms of Auto Immune Diseases
In two scientific studies, intermittent fasting has been found to improve symptoms linked to many different autoimmune conditions such as lupus and multiple sclerosis. This is partly due to the reduction in inflammation markers within the body.
Improved Lung Health
As we have already discussed, fasting helps improve inflammation and combat oxidative stress. Both of these factors are vital for the health of the lungs and can improve the symptoms of chronic lung conditions such as asthma.
Fasting not only has an impact on physical health but also on mental wellbeing. One study from 2013 found that those with depression who tried fasting found that their mood improved over the time period, they felt calmer and had greater levels of mental alertness. All of these factors made them feel better than when they were not fasting.
One natural part of the aging process is that your brain shrinks due to less blood flow to it and the shrinkage of neurons within the brain. Intermittent fasting has been shown to slow down the aging process for the bran and can keep us mentally sharp. This has a positive impact on many degenerate brain disorders such as Parkinson’s Disease and Alzheimer’s.
Simpler Daily Routine
Intermittent fasting is a routine, but it is not a difficult one. The timings are easy to stick to, and you do not need to worry about when to eat and to fit that into your daily plan. Some intermittent fasting plans simply cut out breakfast to extend the fasting time, and this makes the morning routine shorter and easier. Other plans have normal eating days and days with no calorie intake at all, again taking the hassle out of finding time to sit down and eat.
Easier than Dieting
It is a well-known fact that most diets fail. This is because many dieters stick to the plan for a short amount of time, however do not manage to follow it long term as they struggle to change their routines and behaviour. Intermittent fasting, on the other hand, is easier to implement and stick to than diets as you are not restricted in what you are eating. One study found that obese adults found intermittent fasting quick to adapt to, meaning that it was an effective strategy for losing weight.
Doctor Michael Eades, who has personally used intermittent fasting methods, found the difference between them and usual dieting startling. He writes, “Diets are easy in the contemplation, difficult in the execution. Intermittent fasting is just the opposite — it’s difficult in the contemplation but easy in the execution.” Fasting requires a routine, yes, but it is easy to follow without requiring a large lifestyle change, and it does not limit your food choice.
Intermittent Fasting Vs Eating Smaller Frequent Meals
While intermittent fasting has been proven to help with weight loss, there is no similar evidence when it comes to eating smaller, more frequent meals. One study of 16 obese adults found that there was no different in weight or appetite between those eating 3 main meals a day and those eating 6 smaller and more frequent meals.
To back this up, a report from Harvard University found that a 6 month feeding trial focusing on the effects of meal frequency on 51 people found that the time of meals or how often you eat does not impact weight loss. However, those who ate fewer calories for some of their meals did see positive results.
How Intermittent Fasting Preserves Muscle Mass
Most studies linked to intermittent fasting have been focused on weight and fat loss. It is important to note that weight loss does include fat loss, but it can also mean a loss in muscle mass too. Due to this, some studies have shown that intermittent fasters may lose a small amount of muscle (around 1kg) after following a fasting plan for a number of months. Other studies, however, contradict this, having found that there is no loss of lean muscle mass, so there is definitely a need for more research in this area.
Some scientific researchers even believe that intermittent fasting plans are better than non-fasting diets in maintaining muscle mass while losing fat. This is because fasting may increase growth hormone in the body, preserving muscle mass.
Can You Gain Muscle Mass While Intermittent Fasting?
As previously mentioned, there is limited research in this field. One study, which focused on an 8 week training program, saw 18 men split into 2 different groups. One group followed a normal diet, while the other completed periods of intermittent fasting. The results of the study found that the fasting group maintained their muscle mass and increased their strength while the control group gained over 2kg of mass and increased their strengths. This tells us that intermittent fasting may not be the best option if you are looking to build muscle.
This may be due to the fact that intermittent fasting makes it more difficult for the body to get the number of calories and protein that it requires to effectively build muscle.
Accredited Sports Dietician Lisa Middleton states that to attempt to build muscle, you will need to train at full capacity and eat protein and nutrient rich foods when you are not fasting.
Intermittent Fasting Increases Growth Hormone
A 1982 study found that over the duration of a 40 day fast, growth hormone levels increased by around 1250%. A shorter 5 day fast saw increases of around 300%.
The charts above reveal the results from a 1988 study which shows that a day without fasting (control day) has lower levels of growth hormone than days 1 and 5 of fasting. This growth hormone
helps either maintain the muscle mass or at least slow down the loss of it. The increase in growth hormone will also help water regulation.
Intermittent Fasting Decreases Insulin Levels
Any food can raise the levels of insulin in the body, so one of the more effective ways to control insulin levels is to limit food intake. This is because to obtain energy, the body will burn fat and keep glucose levels stable. Intermittent fasting also has this effect as long periods of fasting can reduce insulin levels. This is good for the body as lowering insulin levels can also remove excess water and salt from the body because the kidneys hold excess salt and water when insulin is high. As the salt and water retention reduces, intermittent fasters may experience some fast weight loss.
A 1982 study focused on one patient who was fasting for 40 days. Over the 40-day period, glucose levels reduced, while insulin levels decreased by around 80%, showing the huge impact that fasting has on insulin within the body.
Intermittent Fasting and Skipping Meals
With some intermittent fasting routines, you may be required to skip some meals entirely. While there is a myth that breakfast is the most important meal of the day, it is often missed by people who are too busy to eat in the morning. Studies show, in fact, that 25% of Americans regularly do not eat breakfast. New studies have, however, discovered that breakfast may not be as important as we first thought as it has little impact on metabolism, and when you eat does not make a difference to the calories burned throughout the day.
Additionally, skipping breakfast may reduce the number of calories that you consume in a day by around 400 calories, which can make a big difference over time. One study conducted on obese men and women found that there was no difference in weight between those who skipped breakfast and those who did not, meaning that the body copes while skipping a meal.
Is Intermittent Fasting Safe?
Intermittent fasting is safe if it is done correctly, and it has many benefits that we have already discussed. There is medical literature backing up the benefits of fasting, which cannot be said for many ‘fad’ diets on the market. The reason why intermittent fasting is safe is that it balances periods of eating with fasting, meaning that the body can cope with no food for a short amount of time. Longer starvation periods, however, have negative health effects and can put a strain on the heart.
This advice, however is for healthy individuals who do not have adverse health conditions. Those with low blood pressure or sugar or other health conditions should consult a medical professional before considering a fasting routine.
If you have a history of eating disorders, intermittent fasting should not be undertaking as it can trigger a relapse and hinder your recovery. Additionally, those on medical that needs to be taken with food may not be able to fast for long hours, but there are ways to work your fasting around this – take a look at the most popular fasting plans we explain later in this article.
Finally, any woman who is pregnant or trying to get pregnant should not focus on fasting instead of eating a healthy and balanced diet. New mothers who are breastfeeding should also avoid intermittent fasting as constant nutrition is required as many vitamins and nutrients are passed to babies through breast milk.
What Breaks A Fast?
According to Scott Keatley, RD, of Keatley Medical Nutrition Therapy, consuming any calories counts are breaking a fast as fasting means that you do not eat any kind of food at all. This dispels the rumor that is often cited on the internet that 50 calories break the fast, but anything underneath this amount is fine. Keatley explains that any calories that you eat will be used by the body as energy and therefore count.
Author of The Little Book of Game-Changers, Jessica Cording MS,RD describes how the fasting state is interrupted the minute that you consume enough calories to give your body energy as this is the fuel it needs. She states that there is no clear way to tell if consuming any calories is acceptable as everyone has a different metabolism. Therefore it is best to consume no calories when fasting.
Does BCAA Break Your Fast?
BCAAs are amino acids, which are the building blocks of protein within your body. Due to this, consuming them would be considered as breaking a fast as you are increasing the protein levels within your body. However, some believe that as this is not food, the benefits of consuming them outweigh the negatives as it can support training sessions if exercising during the fasting period.
Does Beta-Alanine Break Your Fast?
While many amino acids will break your fast, Beta-Alanine may just be the exception. This is because it is a modified version that does not help build protein or muscle in the body. Other amino acids such as D-Aspartic Acid and Betaine also fall under this category, so it would be fine to consume.
Options For Things To Consume That Won’t Break Fast?
As we have previously discussed, consuming food during your fast will lead to your fast breaking. It is possible, however to drink liquids in order to keep you going. Scott Keatley suggests that the best liquids to drink are still and sparkling waters as these keep you hydrate but do not contain any calories.
There are some other drinks that contain very few calories that you can consider as they are unlikely to trigger an inulin response. This includes black coffee, which contains around 5 calories per cup and tea which contains less than 5 per serving. It is important, however, to ensure that you do not add anything else to your drinks, such as milk, cream or sugar, as these contain a lot of calories and will break your fast. Sweetener should also not be used as this can trigger a release of insulin in the body, which is counterproductive to your fast. Fasting aims to reduce the levels of insulin in your body, causing the fat cells to be used for energy instead.
Many on online communities suggest drinking bone or chicken broth; however, this contains a lot of protein that will break your fast as it can use this protein as fuel. Therefore, consuming this should be avoided.
Caffeine As An Appetite Suppressant When Intermittent Fasting
As we mentioned above, one cup of black coffee contains only about 5 calories, so it could be consumed during intermittent fasting as an alternative to water. The caffeine in this coffee can also act as an appetite suppressant, meaning that it may make the fasting process easier. Other liquids such as green tea can also lead to a feeling of decreased appetite so are an alternative if you are wanting to avoid higher levels of caffeine.
Intermittent Fasting Methods
There are many different ways to complete intermittent fasting. Every method is effective and has its advantages, however, it is about finding the one that is best for your own routine. Below we have detailed the six most popular intermittent fasting routines to help you work out which fits in with your lifestyle.
The 16/8 Method
The 16/8 method means that you fast for between 14 and 16 hours, meaning that your eating time is reduced to between 8 and 10 hours. The method was made popular by Martin Berkhan, a fitness expert who found this method the best for effective results. What makes this method manageable is that you can fit in your meals during the day, all you may need to change about your normal routine is perhaps missing breakfast or eating it later and not snacking after dinner in the evening.
The timings of the fast can be reduced slightly, and this is recommended for women who may find fasting for between 14 and 15 hours as this works better for them. As with any fasting method, eating healthy food in this window is important as eating high calorie food consistently will not lead to weight loss or improved health.
The 5:2 diet
The 5:2 diet means that a person eats normally for 5 days in the week and reduces their calorie intake to between 500 calories (for women) and 600 calories (for men) for the remaining two days. Made popular by journalist Michael Mosley, the diet is known as the fast diet. It is important to note that this diet has not been tested as much as some of the others on this list, however as it is still a type of intermittent fasting, it is still beneficial.
Eat Stop Eat
The Eat Stop Eat method does exactly what it says on the tin. Fasters will eat normally but stop for a 24 hour fast once or twice per week, then begin eating normally again. Made popular by fitness guru Brad Pilon, this method is one of the most popular on our list. On the days where you are not fasting, the usual amount of food should be consumed. Some do find fasting for 24 hours difficult, however, especially if they jump right in without reducing their eating beforehand. You can build up to 24 hours in small increments if this helps.
Alternate Day Fasting involves fasting every second day. There are two versions of this method, one where the fasting periods involve no calories and one where you can consume less than 500 calories. Again, like the eat-stop-eat method, fasting for 24 hours suddenly can be challenging, so It is recommended that you build up to this.
The Warrior Diet
The warrior diet focuses on eating like the warriors of the past – consuming only raw fruits and vegetables for the majority of the day before eating a large meal in the evening. Made popular by fitness expert Ori Hofmekler, this intermittent fasting method is very similar to the paleo diet.
Spontaneous Meal Skipping
While the other intermittent fasting options on our list are very structured, the spontaneous meal skipping plan can be more flexible. It involves simply missing out on meals every so often. This means you can tailor the plan to when you are too busy to eat or when you are simply not hungry. As with the rest of these intermittent fasting diets, it is important to eat healthily for the rest of the week to gain optimum results.
When Should I Work Out During Intermittent Fasting?
Cardio and HIIT
Completing cardio activities when fasting can show real results, however, it can leave you feeling a little light headed. One way to combat this has been suggested by Schehr, who recommends undertaking high-intensity cardio activities just before you are going to break your fast. This means that you can then refuel and can stop any dizziness. Steadier cardio, however can be completed at any point during the fasting period.
It may take some time to train the body to become used to completing HIIT workouts or intensive cardio while fasting, so build up these workouts over time.
To build muscle, you need to increase your protein and complex carbohydrate intake so that your body is fuelled. It is best to complete strength training directly before or after eating these foods. Therefore it is recommended that you work out either directly before you break the fast or during your eating period to get the best results. Abby Cannon, J.D., R.D., CDN, describes how without the correct fuel, your body will feel depleted, and your workout will not be effective.
Benefits Of Working Out While Fasted
Completing cardio exercises with an empty stomach can aid in weight loss as it accelerates the process. The Journal of Nutrition and Metabolism published a study that found that working out when fasting can boost the oxidation of fat, meaning that the fat stores are reducing. Additionally, it has been found that fasting periods are more effective in helping weight loss than simply just restricting calorie intake.
It is important, however, to assess how your body copes with working out when you are fasting. Once you have discovered this, you can create a personalized workout routine that compliments your lifestyle.
There will be times during an adults life where they have accidentally skipped meals and found themselves unintentionally fasting, however, a structured approach to this can obtain great results. It is important to keep in mind that the process is not perfect for everyone and should only be used if a person is not experiencing adverse health effects from it, such as dizziness.
When fasting, it is important to continue to take on liquids in order to stay hydrated and eat a balanced vitamin, protein and fibre rich diet when breaking the fast. Fasting is a big lifestyle change, and if you have a medical condition or take certain medications, you should consult your doctor before undertaking intermittent fasting.