When you hear the word “fasting,” you probably think of related terms like starvation or hunger. You may also think about religious practices that involve fasting for days or weeks at a time. Though there are many negative connotations to the word fasting, it can actually be a helpful tool for healthy nutrition and weight loss, if you go about it correctly.
Intermittent fasting is a pattern of eating rather than a fad diet. Rather than restricting calories or completely overhauling your diet, intermittent fasting is a way of scheduling your meals to get the maximum benefit from them – it changes when you eat rather than what you eat. When paired with the ketogenic diet, intermittent fasting can be extremely beneficial. Keep reading to learn more.
What is Intermittent Fasting?
A fast is simply a period of time during which you abstain from some or all food and drink. Think about this – when you are asleep overnight you are technically fasting, and when you eat your first meal of the day, you break that fast. This is why the first meal of the day is called breakfast.
Intermittent fasting is a little more complex than that but understanding the difference between your body’s fed state and fasted state is important. Generally speaking, your body’s fed state begins with your first meal of the day and lasts for about 3 to 5 hours while your body digests the food and absorbs the nutrients. In a fed state, your insulin levels are elevated which allows your cells to absorb glucose from the bloodstream. When your insulin levels return to normal after your body has finished digesting, it goes into a fasted state – this usually occurs 8 to 12 hours after your last meal of the day.
When your body is in a fed state, it relies primarily on glucose from the food you eat as a form of energy. In the fasted state, however, your body switches over to burning stored fat – fat that becomes difficult to access when insulin levels are elevated. This is why intermittent fasting is so effective for weight loss – particularly fat loss.
So, how does intermittent fasting actually work?
At its most basic level, intermittent fasting involves alternating between periods of eating and periods of fasting. There are several different patterns of intermittent fasting which can be used to accomplish specific goals. Here is a quick overview:
The 5:2 Diet – This method involves eating normally for 5 days per week and then restricting your calorie intake to 500 to 600 calories for the remaining two days. Also known as the Fast Diet, this plan allows you to choose which days of the week you want to fast – they do not need to be consecutive.
Eat-Stop-Eat – Popularized by fitness pro Brad Pilon, the eat-stop-eat method of intermittent fasting involves engaging in a full 24-hour fast once or twice per week. It is generally easiest to fast from dinner one day until dinner the next day, though you can also do it with breakfast or lunch. This type of fasting can be difficult for some people, so it is recommended that you start with shorter 14- to 16-hour fasts and work your way up.
The 16/8 Method – One of the simplest methods of intermittent fasting, the 16/8 method involves fasting for 14 to 16 hours per day with an 8- to 10-hour eating window. Popularized by Martin Berkhan and known as the Leangains protocol, 16/8 fasting is easy to customize in terms of when you schedule your eating window, and you can divide that window into as many meals as you like.
Alternate-Day – This method of intermittent fasting involves fasting every other day of the week. There are many different versions including some in which you eat normally on non-fasting days and completely abstain from food on fasting days as well as others that allow you to eat 500 calories on fasting days. This method is not recommended for beginners.
In addition to these popular fasting methods, some people also engage in spontaneous fasting – they simply skip meals from time to time when they are too busy to cook or just not feeling hungry. If you want to maximize your results, however, it is best to go with a more structured approach.
What Are the Benefits of Intermittent Fasting?
In the same way that switching from eating primarily carbohydrates to mostly fats can change the way your body works, so can intermittent fasting. When you reduce your food intake for an extended period of time, certain changes occur in the body:
Your insulin levels drop which increases fat burn.
Your body produces more human growth hormone which supports fat burn and muscle gain.
Cellular repair processes occur at a higher rate.
Beneficial changes occur in genes and molecules related to disease prevention and longevity.
The primary benefit of intermittent fasting – at least the one most people are interested in – is weight loss, particularly in the form of fat burning. When you stop eating for an extended period of time, your insulin levels decrease, and your body produces more human growth hormone (HGH) and norepinephrine, both of which facilitate the breakdown of stored fats for energy metabolism. In fact, short-term fasting has been shown to boost metabolism by as much as 3.6% to 14%.
In addition to speeding fat burn and supporting weight loss, intermittent fasting is also beneficial for repairing insulin resistance, reducing oxidative stress, boosting heart health, improving brain function, and preventing chronic disease.
Insulin resistance is a hallmark of type 2 diabetes, and it is caused by chronically elevated blood sugar. When your blood sugar remains high, your body produces more insulin but, over time, the body’s response to that insulin may become diminished. When this happens, it is called insulin resistance. Numerous studies have shown that intermittent fasting can reduce blood sugar levels and insulin levels and, in doing so, help repair insulin resistance and either prevent or help manage type 2 diabetes.
Free radicals in the body contribute to oxidative stress which, in turn, increases your risk for many chronic diseases. Intermittent fasting helps protect the body against oxidative stress by enhancing its resistance – it also helps fight inflammation. By reducing oxidative stress and inflammation, intermittent fasting also supports brain health and function.
When it comes to the benefits of intermittent fasting for heart health, there are many points to cover. Intermittent fasting has been proven to improve numerous cardiac risk factors including blood pressure, LDL cholesterol levels, blood triglycerides, and inflammation. It also helps speed cellular repair processes and slows or stops the growth and spread of cancer cells. Intermittent fasting has shown benefits for other chronic diseases as well which may improve overall health and boost longevity.
How Does Intermittent Fasting Work with the Keto Diet
The benefits of intermittent fasting are undeniable, but how does it work in conjunction with the ketogenic diet?
If you take a moment to think about it, the ketogenic diet actually mimics the physiology of intermittent fasting. By following the ketogenic diet, you are reducing your carbohydrate intake to encourage the body to turned to stored fats for fuel. With intermittent fasting, you are abstaining from food which forces your body to start burning through your fat stores. In both cases, your body turns into a natural fat-burning machine.
Though intermittent fasting can be very beneficial for the ketogenic diet, there are some challenges you should be prepared to encounter. Here are a few things to keep in mind if you’re thinking about pairing the ketogenic diet with intermittent fasting:
You should eat to satiety during your eating window to keep your energy up and to meet your calorie needs – it will also make it easier for you to get through the fasting period.
During fasting periods, drink only water, black coffee, or unsweetened tea – you can also add a little coconut oil or MCT oil if you’re struggling with hunger or low energy. Try supplementing with an exogenous ketone product that contains MCT and BHB, such as Keto Superfuel
Make sure to stay within your macronutrient range while you are in your eating period and aim for balance in your diet to ensure proper nutrition.
If you haven’t tried fasting before, start with a simpler method like the 16/8 method and limit your fasting periods to no more than 12 to 14 hours, working your way up as you’re able.
Be careful about exercising while fasting because you will eventually run out of stored energy – try the targeted keto diet if you plan to exercise fairly often or at a high intensity level.
Some people struggle more than others with intermittent fasting. For example, women tend to do better on shorter fasts (about 14 to 16 hours) than men, though that is certainly not always the case. If you’ve tried intermittent fasting and you find that you just get too hungry, try making sure that your body is keto-adapted before you introduce intermittent fasting. When your body is no longer dependent on glucose, you won’t get as hungry as quickly.
Get Started with a Purge Fast
If you want to try intermittent fasting in conjunction with the ketogenic diet, your primary goal is to enter a state of ketosis as quickly as possible, and one of the best ways to do that is to do a purge fast.
A purge fast simply involves fasting for 3 to 5 days with minimal food and liquid consumption in order to force your body into a state of nutritional ketosis. Once in ketosis, you simply adhere to the ketogenic diet for all of the meals you eat and follow the intermittent fasting method of your choice. If you’ve never done intermittent fasting before, you might consider following a natural approach and listening to your body rather than forcing it to conform to a structured program. If you don’t feel hungry, don’t eat! It can really be that simple.
As you engage in your purge fast, be on the lookout for signs of keto flu as your body burns through your blood glucose and glycogen stores. To help ease the transition, consider taking exogenous ketone supplements to encourage your body to become keto-adapted more quickly.
To give you an idea what a 3-day purge fast might look like, here is a simple plan:
Day 1 (Evening) – Eat a ketogenic dinner that fits your macros and make it your last meal of the day. Go to bed at your normal time.
Day 2 (Morning) – Take a walk within 30 minutes of waking and walk for a total of 3 to 4 hours throughout the day, drinking water as needed. Drink black coffee or plain tea if needed but limit your caffeine intake as much as possible.
Day 2 (Day/Evening) – Consume MCT oil 2 to 3 times throughout the day to elevate ketone levels and prevent fatigue. Engage in activities that will keep you distracted from hunger.
Day 3 (Morning) - Test your blood ketones upon waking. If they are higher than 0.7mmol, keep going with the purge fast. If they are under 0.7mmol, go for a long walk and then retest.
Day 3 (Day/Evening) – Consume MCT oil, or exogenous ketones as needed for energy, drink plenty of water, and keep your electrolytes up by consuming table salt or electrolyte replacement pills.
Day 4 (Morning/Day) - Consume MCT oil, or exogenous ketones as needed for energy, drink plenty of water, and keep your electrolytes up by consuming table salt or electrolyte replacement pills.
Day 4 (Evening) – Break your fast with a ketogenic meal that fits your macros.
Day 5 (Morning) – Start with a ketogenic breakfast and proceed with the ketogenic diet.
The ketogenic diet is a powerful tool for turning your body into a highly efficient fat-burning machine. In addition to supporting weight loss and fat burn, the ketogenic diet can help improve your overall health as well as your longevity. When paired with intermittent fasting, the benefits of the ketogenic diet are amplified, so consider giving it a try for yourself!