What Is Intermittent Fasting?
Intermittent fasting is all the rage right now as an added strategy for nearly all types of diet plans – especially the ketogenic diet. Many studies have shown that intermittent fasting comes with benefits such as improved metabolic health, getting sounder nights of sleep and feeling more energized and awake, improving your body’s immunity against diseases, and of course the best perk — rapid and consistent weight loss. Because of all these benefits, it becomes easy to see why so many like myself have been combining this age old eating schedule with the keto diet to get incredible results.
While intermittent fasting is a proven way to lose weight, it’s best to view it less as a diet and more a lifestyle choice. Intermittent fasting is characterized as a strategic eating pattern where you cycle between periods of eating and fasting. Intermittent fasting does not dictate which foods to eat, but rather specifies at what times you should eat them, or at least how far apart your meals should be. While intermittent fasting doesn’t have any diet guide to stick to, people have seen incredible results when combining it with the regiment of the keto diet.
There are a variety of different types of intermittent fasting methods, which all split the day or week into periods designated for eating and periods designated for fasting. The most popular intermittent fasting method consists of fasting 16 hours per day, and restricting your window for eating within an eight hour period. This is formally known as the 16/8 method, which we’ll get back to later in this article.
“So is intermittent fasting difficult? Fasting for 16 hours per day sounds like a daunting lifestyle choice”
I know what you’re thinking, but intermittent fasting is actually surprisingly simple once you get the hang of it. Timing your eating around your sleep schedule and when to start eating after sleep is one of the key strategies for this diet (after all, the first meal of the day is literally called “break” “fast”). Your body will start to adjust to this schedule, and you’ll start to notice a lot of benefits too. Many people reporting feeling generally better and more energized after they’ve completed their fast.
Hunger can become an issue at first, but a lot of the fight is purely mental, which is why it’s a relief that non-caloric drinks such as water, coffee, and tea ARE allowed during your fasting hours to help fill your stomach. Taking vitamins and supplements is also allowed during fasting, because they contain no calories
How Does Intermittent Fasting Work?
On the surface, fasting can be viewed as a tool that allows the body to utilize its stored energy in more efficient ways, such as burning body fat.
Throughout the intermittent fasting process, it’s also important to understand that fasting is perfectly normal, and in fact, humans have actually evolved to fast for short lengths of time (hours or days) without experiencing any negative long term health repercussions. Intermittent helps to burn fat because body fat is essentially just excess food energy that has been stored for future use. If you don’t eat for short periods of time, your body will start to “eat” its own fat as a source of energy.
Let’s take a closer look into how this works:
When we eat enough food to give our bodies a calorie surplus, more food energy is being consumed than can immediately be used as fuel. Some of this energy then has to be stored as body fat for later use. Insulin is the primary hormone that is involved in this storage of food energy as fat.
At a macro nutrient level, there is a finite storage capacity in our bodies for carbohydrates; and once that capacity has been reached, the liver will start to turn the excess glucose directly into fat, which rapidly accelerates the weight gaining process experienced by people with calorie surpluses.
This process behaves in reverse in cases of intermittent fasting. During periods where we are using energy, but not eating, insulin levels will start to fall, signaling to the body to start burning excess fat for energy, resulting in the weight losing process.
This can essentially be boiled down to two primary states that we are always in: The Fed State (marked by high insulin) and the Fasting State (marked by low insulin). Weight gain and loss is simply based on whether we are in one state more often than the other.
If you normally spend your days eating from the moment you wake up until the moment you fall asleep, you’re always in the Fed State, and rarely the Fasting State (except for when you’re asleep. This means that you’ll have to work twice as hard in your exercise routines in order to get into a calorie deficit to lose weight. And therein lies what makes intermittent fasting such a powerful strategy.
So the science checks out, but how about applying it in real life? Let’s jump into both the pros and cons of intermittent fasting to get a better idea if it’s right for you.
Benefits of Intermittent Fasting
When you switch over to an intermittent fasting diet plan, you’re essentially upgrading a lot of ways that your body operates. Twelve of the most commonly experienced, evidence-backed benefits include:
- Weight and Body Fat Loss
- Lowers Risk of Disease
- Improves Memory
- Eases Depression
- Protects Neurons and Promotes Autophagy
- Slows Down Cancer
- Reduces Inflammation
Weight Loss and Fat Body Loss
Obviously the most popular reason that many people decide to try intermittent fasting is that it’s incredibly beneficial for losing weight. This is both due to the Fasting State and Fed State balance from generating lower insulin levels that I talked about earlier in this article, as well as due to the fact that you’re eating fewer meals (and likely fewer calories) and giving your body more time to turn food into energy while you sleep.
A recent 2014 study even found that intermittent fasting can can lead to an average weight loss of between 3 and 8% over a 3-24 week period, which is a whole lotL
Lowers Risk of Disease
Intermittent fasting has also been known to boost brain health and lower your overall risk for certain neurodegenerative diseases like Alzheimer’s and Parkinson’s. This is because it has the ability to reduce obesity and help protect your body against diabetes, which are both factors that can raise your risk of developing Alzheimer’s.
Because of the reduced insulin and obesity, it also obviously helps to prevent against developing Type-2 diabetes and other cardiovascular related problems like high blood pressure and high cholesterol.
Improves Memory
On top of removing your long term risk of developing memory-related diseases like Alzheimer’s, intermittent fasting can also help with your short term memory skills. A recent 2009 study of 50 elderly adults found that experiencing three months of caloric restriction via intermittent fasting actually boosted memory. This test was measured by their ability to recall certain words.
Another study on mice found that mice that were on a brief intermittent fasting diet had much better learning and memory functions that mice that had free access to food.
Eases Depression
Intermittent fasting has also been known to help with mood disorders like depression and anxiety. A 2013 literature review discovered that people that struggle with depression reported an improvement in overall mood, mental alertness, and a sense of peace when they were fasting. The science backs it up too, as all of the other benefits such as reduced obesity, improved memory, and more energy are all independent contributors to reducing depression and elevating mood as well.
Protects Neurons and Promotes Autophagy
When we fast, the cells in the body kickstart a cellular “waste removal” process that is known as autophagy. Autophagy involves the cells breaking down and starting to metabolize broken and dysfunctional proteins that have started to build up within the cells over time. Essentially, this process helps your body clean out damaged cells and generate new ones. It also helps your body defend itself naturally against disease, which can have a plethora of other positive benefits.
Slows Down Cancer
Intermittent has been shown to have several beneficial effects on the metabolism that can also lead to a reduced risk of cancer. While human studies are still pending, There is some evidence on human cancer patients that shows that fasting was able to reduce various side effects of chemotherapy as well
Intermittent fasting can also specifically slow down the progression of breast cancer and skin cancer by increasing the levels of tumor-infiltrating lymphocytes, which are cells that are sent by the immune system designed to attack the tumor.
Reduces Inflammation
Chronic inflammation is a byproduct of a variety of modernchronic conditions, including gastrointestinal diseases such as Crohn’s disease, arthritis, obesity, asthma and cancer. Furthermore, inflammation is one of the primary causes of musculoskeletal disorders, which can range from short term back pain to more serious chronic arthritis and osteoporosis.
Intermittent fasting has been shown to reduce inflammation at the cellular level, with results at a much larger body-wide level. A recent study showed that fasting can block a part of the immune system that is directly involved with several inflammatory disorders like type 2 diabetes, atherosclerosis, and Alzheimer’s disease.
Side Effects of Intermittent Fasting
While there is clearly a world of benefits that come from intermittent fasting, it also has its side effects, and it’s important to remember that it isn’t entirely risk-free. Before jumping into a fasting diet, you may want to consult with your doctor, because there are lots of other mitigating factors such as personal medical history and blood sugar levels that need to be taken into account first. Recent research also strongly recommends talking to a doctor before starting fasting if you’re taking any other medications, as many medications require strict eating schedules that may not always work out with the new schedule of intermittent fasting.
Personal medical history, medications, and blood sugar situations aside, there are a few universal side effects that you might want to prepare for if you do decide to go all in on intermittent fasting. These include:
- Excess Feelings of Hunger
- Likelihood of Overeating is Increased
- Increased Irritability and Fatigue
- Increased Chances of Becoming Dehydrated
- It Can Affect Your Social Life
- Potential Digestion Issues
Excess Feelings of Hunger
Of course it’s to be expected that once you start transitioning to a new type of eating schedule, you’ll probably have some new bouts of hunger on a day to day basis. This doesn’t last forever, as your body does get quickly used to the fasting routine, but the first few days or even weeks can be a struggle to fight off cravings. The best way to combat this is to eat well balanced and nutritional meals during your feeding periods so that your body has the energy it needs to operate normally during fasting periods.
Likelihood of Overeating is Increased
With increased hunger during periods of fasting, comes more ravenous eating during times of feeding. A lot of people make this mistake and “binge eat” within their eight hour window, resulting in a caloric surplus that actually makes it harder for their body to burn fat. If you know that you are a stress eater, you should definitely avoid certain things that spike your stress levels, especially during times right before eating, or you’ll likely overeat.
Increased Irritability and Fatigue
It’s perfectly normal to feel tired and even fatigued when you first start trying out intermittent fasting, and especially if you’re combining it with the keto diet. You may even experience some mild mood swings and start to feel more irritable. This is because your mood is closely tied to your appetite, and until it adjusts, those extra bouts of hunger could also contribute to that “hangry” feeling we’ve heard so much about.
A good way to overcome this is to focus on getting enough rest at night, which is the most important part of your fasting phase. I personally like to use melatonin to get sounder nights of sleep so that my body is well-rested and equipped to handle my fasts. (I prefer the Pure Encapsulations Melatonin from Amazon.com).
Increased Chances of Becoming Dehydrated
Intermittent fasting has also been found to lead to increased chances of becoming dehydrated. This is simply because when you’re not eating, it’s easy to forget not to drink the right amount of water every day either. To stay on top of this, I always try to keep a reusable water bottle with me at all times as a reminder, and also like to supplement my diet with electrolytes for extra hydration assurance.
It Can Affect Your Social Life
This is one of the main worries I’ve noticed from friends that ended up not following through with intermittent fasting. It can be very challenging when most of our social activities are based around food and drinks. However it is still possible, and once your body fully adjusts, those temptations will start to become easier to manage. I’ve gotten really into different types of tea as a way to both stay hydrated, and to have something to hold onto and drink while at parties or hanging out with friends.
Potential Digestion Issues
It’s also possible to experience digestion problems when switching to consuming larger portioned-sized meals than you’re used to, and especially when you have to eat all of your food within a shorter time frame Larger amounts of food that you eat also means your body will require to more time to digest, which can put added stress on your GI tract, leading to symptoms like nausea, indigestion, and bloating.
What are the Different Types of Intermittent Fasting?
There are several different ways that intermittent fasting can be applied to a daily lifestyle. The main methods include:
- The 16/8 Method
- Alternate Day Fasting
- The Warrior Diet
- OMAD (One Meal A Day)
- Eat-Stop-Eat
The 16/8 Method
This method is by far the most popular, and involves fasting every single day for around 14-16 hours, and then restricting your daily “eating window” to just 8-10 hours. This is the most optimal way to fast intermittently to yield the most results. While the fasting window may seem daunting, it can be simply done by just eating an early dinner and a late breakfast, to use your sleep schedule to bear the brunt of those 16 hours. As I mentioned earlier, it’s important to get a nice balance of nutrient-rich foods in during your eating window, to avoid binging over overeating, and to stave off cravings during your fasting window.
Alternate Day Fasting
This type of intermittent fasting is one of the fastest growing methods to be studied, as it brings a lot more convenience to the standard eating plan. Alternate Day Fasting requires alternating between feeding and fasting days. On a usual fasting day, there is one designated meal at lunch time that will typically consist of approximately 25% of the caloric needs based on the individual. This type of fasting involves what is known as “modified fasting”, which utilizes different durations of fasting from anywhere between 30-40 hours based upon the individual’s schedule and dietary needs.
There are a few different variants of the alternate day fasting schedule, as some will even allow up to 500 calories to be eaten on fasting days.
The Warrior Diet
The Warrior Diet is a recent popular diet that consists of eating small amounts of raw fruits and vegetables during the day, and then eating one huge meal at night. Essentially, you are meant to “fast” all day, and “feast” at night within a four hour eating window. The diet is also similar to that of the Paleo diet, which consists of eating whole, unprocessed foods.
You can learn more about it from its author and fitness expert Ori Hofmekler in his book, The Warrior Diet.
Eat-Stop-Eat
The Eat-Stop-Eat form of intermittent fasting consists of a 24-hour fast, which is performed either once or twice per week. It is typically recommended to fast from the the end of one dinner one day to the next dinner on the next day, but you can also fast from breakfast to breakfast or from lunch to lunch. Similar to the standard intermittent fasting strategy, water, coffee, and other non-caloric liquids are allowed during the phasing stage of this method.
You can learn more about Eat Stop Eat with this comprehensive guide.
You can check out some other intermittent fasting styles from our friends at Gravity Transformation here:
Is Intermittent Fasting Safe on Keto?
It is perfectly safe to undergo intermittent fasting while sticking to the keto diet. Utilizing the keto diet and intermittent fasting in unison is a great way to scale up your weight loss and fat burning results. Because the keto diet is already designed to force your body into running off of ketones instead of carbohydrates, you’re already “fasting” in a sense because you’re restricting the amount of carbs and glucose that you’re consuming. This means that if your goal of the keto diet is to enter ketosis, then intermittent fasting can help you get into ketosis even quicker.
There are some risks that go hand in hand with both, but these should not be deterrents as long as you are getting the right nutrients in your diet during your eating window. For the majority of people, there are no long term health risks in combining the keto diet with intermittent fasting. However if you experience seizures, struggle with diabetes, or have any sort of cardiovascular issues such as high cholesterol or high blood pressure, you may want to consider consulting with your doctor before fully diving into both.
I’ve personally found that it was easier to start with the keto diet, so that my body could fully get into ketosis and get used to my new eating habits. Once fully in ketosis, strategizing my eating window became a lot more manageable, especially when I knew just exactly how much to work out, how much water I needed to stay hydrated, and kept close track of all my intake of macro nutrients.
Next, we’ll take a deep dive into the benefits of combining these two, and get into the details on why keto and intermittent fasting together can be a dynamic duo when it comes to getting into the state of ketosis.
Benefits of Combining Keto and Intermittent Fasting
Keto and intermittent fasting are a great way to scale up your fat burning process. Some of the specific benefits of combining the two diet methods include:
- Hunger Suppression
- Cravings Suppression
- Increased Ketone Levels
- Accelerated Fat Loss
Hunger Suppression
Both the ketogenic diet and intermittent fasting have been proven to help to suppress hunger on their own. On a keto diet, your liver transforms fat into little bundles of energy called ketones, which it then transmits through your bloodstream for your cells to utilize as fuel instead of fat and sugar. Ketones are also known to suppress ghrelin, which is your body’s primary hunger hormone. High levels of ghrelin is usually responsible for experiencing hunger. On keto, your ghrelin levels will stay consistently low, even if you don’t have food in your digestive system. Fasting when combined with keto gets significantly easier, so that you can fast for longer periods of time in order to reap all of the combined benefits.
Cravings Suppression
Replacing sugar and carbohydrates with fat via the keto diet is beneficial because fat inherently doesn’t spike your blood sugar levels like carbohydrates do. If you combine a keto diet with intermittent fasting, your blood sugar levels will be able to stay stable and stay in a low, healthy range for the whole day. This consistent level is a great way to suppress cravings for sweet and sugary snacks.
Increased Ketone Levels
While there isn’t an abundance of medical research that shows the specific benefits of comining intermittent fasting and the keto diet, it is fairly clear that ketone levels will rise when these two dietary plans are followed simultaneously. This combination can help accelerate weight loss, because the higher level of ketones in your body, the more efficiently it will utilize your macro nutrients and keep you lean.
Accelerated Fat Loss
The combination of the keto diet and intermittent fasting is often described as a a one-two punch method for losing weight quickly. Fasting and the keto diet both have the potential to spontaneously increase fat loss, even when people that utilize these techniques don’t necessarily restrict their caloric intakes. When you put intermittent fasting and keto together, your body essentially becomes a fat-burning machine. The excess weight will come off very quickly, and because the keto diet also suppresses the hormone ghrelin, you don’t experience nearly as much of the hunger and feelings of food deprivation that typically go hand in hand with most weight loss strategies.
Side Effects of Combining Keto and Intermittent Fasting
When it is combined with a high fat, low carb diet such as keto, intermittent fasting’s side effects can be more pronounced than they would be just on their own. You may want to look out for some of the following symptoms:
Fatigue
When combining keto and intermittent fasting, you’ll likely experience a loss of excess water and will be more prone to dehydration. This is because with excess water, your body also will flush out vital electrolytes such as potassium, magnesium and sodium. Your body also needs to be able to produce sugar to use as energy when fasting, so it will naturally start a process known as gluconeogenesis. During gluconeogenesis, your liver converts any non-carbohydrate materials such as lactate, amino acids, and fats completely into glucose. As this takes place, your basal metabolic rate will utilize less amounts of energy than normal, and your blood pressure and heart rate can become lowered lowered. During this state, you’ll likely notice some increased fatigue.
Hypoglycemia
When you first start intermittent fasting with keto, your body will need some time to process glucose levels while without food for over 12 hours. Even though you are taking in a ton of calories via macronutrients like fat and protein, you’ll still likely experience some low energy, exhaustion, dizziness, and general low blood sugar levels. Headaches are another symptom that tend to flare up as a byproduct of hypoglycemic episodes, but they will eventually subside once your body is generating enough ketones.
Muscle Cramps
That same lack of hydration can also lead to small, temporary muscle cramps in some people when they are in a state of fasting ketosis. Certain pains and aches can also be brought on by malnourishment and insufficient levels of those important mineral nutrients such as magnesium, potassium and calcium. Your level of electrolytes not only is connected to fatigue and dehyrdation, but it can also contribute to frequent muscle cramping. One of the best ways to replenish these electrolytes is by drinking enough water, and getting the right electrolyte supplements. I personally use the Ultima Replenisher Electrolyte Powder. (Check it out here on Amazon.com)
Muscle Loss
Inherently, fasting doesn’t directly burn muscle mass. In fact, human growth hormones and ketones are protein sparing, which means that they preserve lean tissue at the expense of increased fat burning. But because of gluconeogenesis, you may be subject to some light muscle loss. Training in a fasted state will actually result in a greater anabolic response once you start eating again. This is a great way to build up muscle, but muscle loss can also be prevented by getting enough sodium and rest between workouts and fasting periods.
Keto Fasting Tips
As I mentioned above, there are multiple variations of intermittent fasting styles that you can try out with keto, and each come with their own pros and cons. The best way to figure out which fasting window works best for you is to simply pay close attention to how your body feels on a day to day basis. For optimal results, you should take note of your energy levels, hunger levels, cognitive function, and quality of sleep each night.
If you yourself starving over the duration of the day the day, or if you can barely make it through an entire workout without experiencing intense fatigue and dehydration when you’re fasting, you may need to experiment with shortening your fasting window, and then gradually increasing it by about one hour each week to get your body more adjusted. Alternatively, you can also reduce the amount of days that you fast each week. It’s also vital to make sure that you are getting enough calories during your feeding window, and that those calories contain the right macronutrients for optimal energy conversion. Working with a dietician or nutritionist, or really any health care professional can greatly help you to determine the specifics of exactly how many calories your body uniquely needs per day, based on your personal body composition, activity level, amount of sleep you get every night, and any other contributing lifestyle factors.
One of the best ways to get started with intermittent fasting is to set up a schedule and to try and stick to it. Some of my favorite ones that I’ve used before include:
- Eat from 12-8 pm, and then fast for 16 hours (also referred to above as the 16/8 method).
- Eat from 9am-7pm, and then fast for about 14 hours.
- Eat from 9am-9pm, and then fast for 12 hours.
If you’d like to dive deeper into keto and intermittent fasting, you should check out these great free ebooks from KetoResource.
Case Study (With Results)
The great thing about the combination of keto and intermittent fasting is that its tried and true. Thousands of people have seen weight loss success with these methods every year. Here are a couple of my favorite stories of results.
YouTuber SlayThisDebt has an incredible success story, losing over 25 pounds in just 6 short weeks by combining Keto and Intermittent fasting. Check out her story here:
YouTuber DajjaD also has a super interesting story about how he balanced keto and intermittent fasting with his full time job, and was able to lose over 40 pounds in just six weeks.
YouTuber Beauty By Shabree has a similarly inspiring story, in which she was able to lose 60 pounds all with keto and intermittent fasting. She gets into her daily schedule, struggles and obstacles she had to overcome, and has some of her own useful tips for combining these methods.