Intermittent Fasting: Fad or Fact?
What is intermittent fasting? Does intermittent fasting work? And what are the health benefits?
You’ve likely heard of a little something called intermittent fasting and all of its incredible health benefits. It has been said to be the key to weight loss, lower your risk of chronic diseases, increase energy and even give your brain a boost, but can it be so? How exactly does it work? And is it beneficial for everyone? In order to answer those questions, allow me to breakdown the basics of intermittent fasting, what it is, how it works, who can use it, and who should avoid it.
What is Intermittent Fasting?
Put simply, fasting is any time that you are not eating. Intermittent fasting (also known as IF) is precisely what the name implies, fasting, but not continuously, and is used to describe several different approaches to strategic short-term fasting, as intermittent fasting does not involve fasting for prolonged periods of time. Regardless of how someone chooses to execute it, intermittent fasting is an eating pattern that cycles between periods of eating and periods of fasting throughout the day. Essentially, it is a pre-determined window of time that you will go without food; intermittent fasting doesn’t change what you eat, it changes when you eat.
How Does Intermittent Fasting Work?
The most basic form of intermittent fasting is a 12 hour fast; you eat dinner at 7:00 pm and you don’t eat again until 7:00 am the next morning at breakfast. In fact, this is where the term break·fast originated, it is the meal that breaks your fast every morning, implying that this is actually a natural part of everyday life. In addition to this most basic form of fasting, there are many other ways that you can execute intermittent fasting and involve extending the standard overnight fast to anywhere from 16 to 24 hours. Some of the more common methods are known as the 16:8; you eat during an 8-hour window and fast for the remaining 16 hours of your day; the 20:4 method (or Warrior Diet) where you fast during the day and eat a huge meal at night; the eat-stop-eat method which involves a 24-hour fast either once or twice per week; and finally, the 5:2 method which includes 5 days of regular eating along with 2 days of complete fasting each week.
The human body only exists in two states; 1) the fed state and 2) the fasted state; you are either eating and storing food energy, or you are fasting and burning the food energy you have stored. The process of intermittent fasting is simply a strategic approach to utilizing these two states and involves extending the fasting state to allow your body to utilize the food energy it has stored for longer periods of time.
Is it Natural to Intermittent Fast?
From an evolutionary perspective, it is in fact completely natural for humans to fast, and it is not natural for humans to eat all day long, nor is it necessary. Going for extended periods of time without eating was completely normal for our hunter-gatherer ancestors; if a hunt wasn’t successful, food would not have been available, so we have biologically adapted to this process. The human body is equipped with built-in mechanisms that allow us to function optimally both when we are eating and when we are not eating. In fact, you can see fasting practised for religious and spiritual reasons in many different cultures around the world.
Intermittent Fasting vs. Caloric Restriction
One thing that is important to note is that there is a big difference between intermittent fasting and caloric restriction. Intermitting fasting is not about eating less food, it is about eating it during a specified window of time. For instance, if someone is executing a 16 hour fast (or 16:8 method), they may still eat the same volume of food (or number of calories) they were previously eating, they are simply restricting it to an 8 hour period of time. Another important thing to note is that the foundation of intermittent fasting is built on whole foods, so when you do eat, you are consuming nutrient-dense whole foods, not packaged, refined or processed foods. On the contrary, caloric restriction is simply about eating less calories or less food, and does not address the quality of food you are eating or the time at which you are eating it.
The Benefits of Intermittent Fasting
As you can imagine, when done properly, there are many benefits to intermittent fasting which include:
- Weight & Fat Loss: During a fast, your cells switch from using glucose as their primary fuel source to using fat. When you digest food, carbohydrates are broken down into sugar which is used as a source of energy for your cells, however, any excess energy is stored in fat tissues to be used when food is no longer available. Therefore, when you are fasting, fat stores and triglycerides are burned for energy which is why intermittent fasting has been shown to support weight loss.
- Improved Insulin Sensitivity: Insulin is known as an energy storage hormone and every time that you eat you trigger an insulin response. Because insulin regulates whether extra glucose from food is stored in the body as fat, fasting can help to improve insulin sensitivity and further support weight loss.
- Improved Circadian Rhythm: Proponents of intermittent fasting note that creating a regular routine and specific timing around food helps us to regulate our internal clock. Evolutionarily speaking, we are designed to eat during the day and fast during the night, which helps to regulate our circadian rhythm keeping us energized and sleepy at the appropriate times of the day.
- Increased Cellular Resiliency: When fasted, our cells initiate a cellular repair process which initiates a waste-removal process called autophagy. During autophagy, the body “cleans house” and regenerates, which eliminates dysfunctional and damaged cells and creates new healthy ones.
In addition to these benefits, other possible benefits of intermittent fasting include reversal of type 2 diabetes, improved mental clarity, reduced inflammation, increased growth hormone, improved blood cholesterol profile, and reduced risk of Alzheimer’s disease.
Reasons NOT to Intermittent Fast
As you can also imagine, intermittent fasting is not for everyone. In fact, when it comes to diet and nutrition there is no one-size-fits-all solution. Intermittent fasting is not recommended for people who:
- Do not eat a whole foods diet
- Have a history of eating disorders
- Have a medical condition or take medication
- Have hormonal imbalances
- Suffer from chronic fatigue or HPA axis dysregulation
- Struggle with high levels of stress
- Struggle with binge eating
- Women who are trying to conceive
- Women who are pregnant or breastfeeding
Additionally, although intermittent fasting can support weight loss, I am cautious to recommend it strictly as a weight loss tool as it can easily be abused and is not the singular purpose of fasting. If for any reason you are unsure if intermittent fasting is right for you, I encourage you to speak with a health professional before jumping in.
The Bottom Line: Does intermittent fasting work?
Intermittent fasting most certainly has its benefits and can work well as a tool for many people. At the most basic level, ensure that you are implementing a standard 12-hour fast regularly. Remember, there is no need to eat breakfast (i.e. break the fast) unless you are actually fasted, and I would argue that many people can benefit from simply implementing a standard 12-hour fast daily and may never need to implement longer forms of fasting. However, if want to dabble in fasting, once you are able to implement a standard overnight fast you can begin by simply extending your fast to 14 hours or 16 hours and see how things go. There is no need to jump directly into a 24-hour fast or utilize the 5:2 method, in fact, they may not be necessary at all.
Regardless of what you choose, always make sure that you are doing things safely. Do your research and speak to a health professional to ensure that you are doing what is right for you, and choose a method that fits your lifestyle. Like any diet tool, intermittent fasting is only as effective as you allow it to be, so focus on creating a solution that works for you.
For more information on this topic, please refer to my interviews Dr. Jason Fung: