Intermittent fasting (or IF) has quickly become one of my go-to methods for losing weight since I first tried it. As effective as it is, it is probably even easier to understand, especially when reduced to its bare essentials.
Seriously, it's not that difficult. However, there are a few key points you should be aware of in order to learn how to do intermittent fasting for serious weight loss.
This article will go over all of the important details, such as how it works, its benefits, the various types of intermittent fasting, and how you can successfully combine it with other weight loss techniques.
Let’s get to it!
How does intermittent fasting work for weight loss?
Intermittent fasting works as an effective weight loss tool because it discourages overeating. And, because you eat less food, you consume fewer calories, which leads to weight loss.
However, in more scientific terms, intermittent fasting works by influencing our hunger hormones — insulin, ghrelin, and leptin, to be specific — which affects how we metabolize energy.
When it comes to energy, we get it from the food we eat in the form of glucose. Carbohydrates are our body's primary and preferred source of energy, but protein and fat are also converted into glucose.
When you have glucose in your bloodstream, your body responds by releasing insulin.
Insulin aids in the storage of glucose in your muscles, where it can be used immediately, or in your liver, where it is stored as energy reserves known as glycogen. When your muscles and liver are both full, your body begins to store excess glucose as fat.
Having said that, research indicates that insulin reduces ghrelin (the hunger hormone) while simultaneously increasing leptin (the satiety hormone), making you feel full and satisfied.
This hormonal cascade is a big part of why intermittent fasting works so well for weight loss, but it's not the whole story.
In theory, the prolonged fasting period of IF deprives your body of a consistent source of glucose, forcing it to rely on glycogen stores. When that is depleted, your body will begin to burn fat for fuel (sort of like the ketogenic diet which we will also discuss later on).
So, aside from losing weight…
What are the benefits of intermittent fasting?
Overall, intermittent fasting has many of the same advantages as most other diets. These are some examples:
- Total cholesterol levels have decreased.
- “Bad” cholesterol levels are lower.
- Triglyceride levels are lower.
- Insulin and blood sugar levels are both lower.
- Improved blood pressure
Furthermore, evidence suggests that improving the aforementioned levels coincides with lower levels of inflammation. Finally, all of these will help you avoid chronic diseases such as diabetes, heart disease, rheumatoid arthritis, cancer, and others.
According to one study, the benefits of intermittent fasting stem primarily from its effectiveness as a weight loss agent, because these effects are similar to those of other diets.
Whatever the reason, I believe that the best aspect of intermittent fasting is its simplicity.
So, here's how you do it correctly:
How to Perform Intermittent Fasting Properly
Unlike most other diets, which have a slew of restrictions and require you to eat only certain types of food, intermittent fasting isn't all that difficult. The only fundamental intermittent fasting rules to remember are:
- Consume few, if any, calories during your fasting period, and consume the majority, if not all, of your nutrients during your feeding window.
Of course, there are a few other auxiliary rules to follow if you want to lose weight (we'll go over those later), but they apply to any diet.
In addition, if you're wondering “how many hours should you do intermittent fasting to lose weight?” And the answer to the question “how many meals can you eat while intermittent fasting?” depends entirely on the type of intermittent fasting you practice.
Each type has its own set of rules, so choose the one that feels the most natural to you.
Here are your options:
The various types of intermittent fasting:
Overall, there are seven popular intermittent fasting schedules to choose from. They all have different fasting patterns, with some using hours, others using days, and still others using meals.
Let's start with those who have an hourly fast-feast pattern.
The 12:12 method
The 12:12 method, also known as overnight fasting, involves fasting for 12 hours and eating for the remaining 12. That is, if you stop eating at 8 p.m., you can eat again at 8 a.m. the following day.
Many people, including myself, believe that this is the most beginner-friendly type of intermittent fasting because, if done correctly, sleep does the majority of the fasting for you.
16:8 intermittent fasting
You fast for 16 hours and have an 8-hour eating window when following the 16:8 diet. For example, suppose you eat from 12 p.m. to 8 p.m. and then fast for the rest of the day.
This is a slightly more difficult fasting method than 12:12, but it is still relatively simple.
This method works best for me because it fits into my schedule. I simply skip breakfast, eat a substantial lunch, a lighter dinner, and possibly a couple of healthy snacks in between.
It's fine if you don't want to skip breakfast. You could also eat your breakfast at 8 a.m., your lunch at noon, and your dinner at 4 p.m. If this is your preference, I recommend eating foods that suppress your appetite for dinner to help keep you full until you can eat again in the morning.
The Warrior Diet (20:4 method)
This version includes a 20-hour fast followed by a 4-hour eating window. As a result, it is sometimes referred to as the 20:4 method.
It's said to be based on how warriors/hunters ate very little during the day while performing their duties and then feasted at night when they were finished.
I'm not kidding when I say that I tried this version of intermittent fasting because I wanted to feel like a member of King Leonidas' army in the film 300. I don't know how to wield a sword, and my neighbors would think I was insane if I yelled a battle cry, so I tried the warrior diet instead. (Cue Gerard Butler yelling, “Tonight we dine in hell!”)
I ate my day's worth of food from 4-8 PM, slept, skipped the next day's breakfast, lunch, and everything in between, and then began eating again from 4-8 PM the next day. Of course, you can tailor your 4-hour eating window to your specific schedule.
The 5:2 method of fasting
Because you won't be counting hours, the 5:2 method is a little different. Instead, you will eat for five days and fast for two.
In general, the 5-day eating window allows you to eat “normally.” However, if you consider normal to be clearing out the junk food aisle and eating fast food for all of your meals, you may want to reconsider your habits. You might lose some weight this way, but it won't be healthy or sustainable.
In addition, the 5:2 method's 2-day fast allows you to eat a quarter of your normal intake. So, if you normally consume 2000 calories per day, you would have to limit your food intake to 500 calories on abstinence days.
Granted, a quarter of your normal calories isn't much, but you still get to eat.
I see eat-stop-eat as a variation on the 5:2 diet, in which you fast for 24 hours once or twice a week. The difference is that eat-stop-eat requires you to consume no calories for a full 24 hours, whereas 5:2 allows you to consume a few calories. The former is slightly more difficult to follow as a result, but it is still very doable.
Because fasting for 24 hours does not necessarily imply that you cannot eat anything for the rest of the day. As an example:
- On Monday, you begin fasting at 12 p.m.
- This allows you to have an early lunch and an on-time breakfast.
- On Tuesday, at 12 p.m., you will break your fast.
- This gives you a full 24-hour fast as well as enough time to eat a late lunch and a regular-time dinner.
Of course, feel free to make changes. If it is more convenient for your schedule, you can fast from breakfast to breakfast or dinner to dinner.
- This gives you a full 24-hour fast as well as enough time to eat a late lunch and a regular-time dinner.
In any case, I recommend that you do not schedule your fast days consecutively for either the eat-stop-eat or 5:2 methods. Instead, allow yourself 2-3 full days of eating in between fasts. This, I believe, makes it easier to follow and more long-term sustainable.
Here is a sample weekly schedule that you can refer to and modify as needed:
Occasional meal skipping
Along with 12:12 and 16:8, I believe this is one of the simplest IF methods to follow.
It's ideal for beginners because it's literally just skipping meals on occasion. There is no actual structure to it, so you do not have to choose a specific meal or day to fast. Simply do it when you aren't as hungry or when you believe you can go without food for a period of time.
Feeling a little peckish for dinner? Ignore it. Isn't it true that you're too busy to make breakfast today? Ignore it.
The only other rule you should follow here is to aim for at least one to two missed meals per week.
Alternate-day fasting (ADF)
At its core, ADF is simply fasting every other day. It does, however, have a few different names and sub-variations.
For example, a more extreme approach would be to refrain from consuming any type of calorie on fasting days. You could also consume 25% of your normal daily calories, or 500 calories regardless of what you consider normal.
Whatever path you take, the end result should be consuming significantly fewer calories for the entire week, resulting in weight loss.
This leads us to the following question:
Which intermittent fasting method is the most effective for weight loss?
In terms of consuming the fewest calories, alternate-day fasting appears to have the greatest potential for weight loss, especially if you choose not to eat on your fasting days.
Given that you ate your normal number of calories on your eating days, this version of ADF effectively cuts your weekly caloric intake in half, resulting in rapid weight loss. Even if you did eat a few calories during your fast, you'd still be reducing your overall intake by several orders of magnitude.
However, the drastic reduction in both weight and calories means that it is not sustainable for the majority of people. According to the CDC, a healthy weight loss is defined as losing 1-2 pounds per week — and you'd most likely lose more with ADF. It's also one of the more difficult ones.
That being said, I believe the best intermittent fasting method for weight loss is one that provides gradual yet sustainable weight loss results while remaining relatively simple.
In my opinion, 12:12, 16:8, 5:2, and spontaneously skipping meals fit the bill, so try those first.
And, while we're on the subject of sustainability…
Is it possible to fast intermittently for an extended period of time?
The short answer is, yes. Probably.
But here's the long answer, and the reason it's a little complicated:
According to Dr. Donald Hensrud of the Mayo Clinic, very little research has been done on the long-term effects of intermittent fasting. I checked, and sure enough, I couldn't find anything. As a result, we can't really look too far into the future here.
However, based on what I've learned, the problems with the long-term effects of intermittent fasting stem from the fact that some of the methods necessitate extremely low calorie intake. More research isn't needed to demonstrate how this is both unhealthy and unsustainable.
Another issue is the assumption that IF dieters can eat whatever they want and as much as they want during their non-fasting hours. This can result in malnutrition, which is both unhealthy and unsustainable.
Have the foresight to do the following during feeding times:
- Control your portions and eat nutritious, well-balanced meals made from whole foods.
Let's get a little more specific, shall we?
How to Get the Most Out of Intermittent Fasting
First, let’s talk about portion control.
According to the Mayo Clinic, for a healthy weight loss, you should cut 500-1000 calories per day.
However, given that some intermittent fasting methods require you to eat little to no calories on certain days, aim for the weekly equivalent of eating 500-1000 fewer calories per day. At the end of each week, that equates to 3500-7000 fewer calories.
That amount should still result in a safe 1-2 pound loss per week.
Following that, consume nutritious and well-balanced meals.
While the ability to eat whatever you want is certainly how some people promote intermittent fasting, it is not how you should approach it if you want to maximize its effectiveness over time.
Rather, opt for whole foods that provide adequate nutrition. These include fruits and vegetables, lean protein sources, healthy fats, and the appropriate amount of carbohydrates.
Look over our list of foods to eat when trying to lose weight and incorporate them into your eating plan.
Another way to make the most of intermittent fasting is to combine it with other weight loss techniques such as keto and weight lifting.
This brings us to the next section.
Is it possible to do intermittent fasting while on a keto diet?
Absolutely. In fact, the entire theory behind how intermittent fasting increases fat burning is that the prolonged fasting hours force your body into a temporary state of ketosis in which you use your own fat for energy.
However, if you intend to follow the ketogenic diet, you could ease into ketosis through intermittent fasting.
When you're in ketosis, you can either eat normally or continue using IF methods while eating keto-friendly foods.
Is it possible to fast intermittently while lifting weights?
You certainly can, sir. Not only that, but this combination has long been popular in the fitness community. However, there are a few changes you must make:
- One, you must plan your workouts around your diet, and two, you must modify your macronutrients.
When it comes to scheduling your workouts…
Please, please, please do not exercise on fasting days. It is simply ineffective.
To grow and/or repair your muscles, your body requires carbohydrates, fat, and protein. So, if you eat less than 600 calories per day, you simply cannot provide your body with the raw materials it requires.
Instead, schedule your workouts on days when you can eat before and after.
To give you a better picture, let's add a workout split to the 5:2 and eat-stop-eat sample schedule I showed you earlier:
|Day of the week||Fast or Eat||Workout or Rest|
This concept, of course, applies to other methods as well. Adjust the workout split as needed.
In terms of adjusting your macronutrients…
I'm assuming you lift weights and fast at the same time because you want to lose weight while retaining as much muscle as possible. After all, that is the combined goal of these two.
However, according to research, a bodybuilder's total calories should consist of:
- Carbs: 50-60%
- Protein: 25-30%
- Fat: 15-20%
Even if you aren't a bodybuilder, I believe you should use these numbers as a rough guide whenever you are in your feeding window.
The higher protein intake will provide your muscles with the amino acids they require to repair themselves, the carbs will ensure you have energy to fuel your workouts, and the fat will help you manage your hormones.
Intermittent fasting and its various methods are, in my opinion, truly fascinating. You can use IF alone to lose weight by simply reducing your calorie intake, or you can combine it with exercise and other weight loss methods to maximize its already enormous potential.
The key here is to make sure you choose the right type for you, don't overeat during feeding times, and eat healthy food whenever you do eat.
And with that, I'll say good-by. Please do me a favor and forward this to your friends. Awesome!