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The Ultimate Guide to Intermittent Fasting for Fat Loss

If you’ve surfed Google or YouTube searching for weight loss solutions, you’ve likely come across a “magical” fix known as Intermittent Fasting or IF.

To some, it’s the perfect way to lose your strength, kill off your muscle mass, and end up skinny and frail - to others it’s the holy grail of fat loss and focus, and the closest we’ll get to the fountain of youth.

Today we are going to look at intermittent fasting, objectively. We are going to discuss:

  • What intermittent fasting is
  • How intermittent fasting works
  • The pros and cons of IF
  • And more!

By the end of this article you’ll have all of the information necessary to make a well informed decision about whether or not intermittent fasting will help you, or hurt you, regardless of what your goal is. (If you're looking to build muscle with IF, read this.)

First things first…

What is Intermittent Fasting?

It’s all in the name.

Intermittent: occurring at irregular intervals; not continuous or steady.

Fasting: to abstain from all food.

Put them together and you’ve got a diet where you’re cycling between periods of fasting and non-fasting.

Typically, one will choose a specific time of the day where they’ll fast, and allot all of their meals to the remainder of the day. The purpose is simple: minimize the amount of time spent eating in order to restrict caloric intake.

For example: one of the more popular approaches to IF requires a 16 hour fast followed by 8 hours of which you can fit your meals. Others are a bit more extreme with their approach and require a 20 hour fast – allowing just 4 hours for consuming calories.

Simple enough, right?

Intermittent Fasting for Fat Loss

intermittent fasting for fat loss

How Intermittent Fasting Works for Fat Loss?

The mechanism by which IF works for fat loss is actually quite simple. You see, every day our bodies go back and forth from a fed state to a fasted state – the purpose of intermittent fasting is to extend the time we spend fasting. Because most people begin eating early on in the day and stop eating late at night, we tend to spend more time fed than fasted. On average, people are consuming food for 13-14 hours, intermittently, and fasting only about 10-11 – most of which is during sleep.

By allowing us to spend more time in a fasted state, we are, effortlessly, reducing the amount of food we’re consuming on a daily basis, thus reducing our overall energy intake – or at least that is the idea.

Nothing magical there…

In fact, a review done by scientists from the University of Sydney suggested that "While intermittent fasting appears to produce similar effects to continuous energy restriction to reduce body weight, fat mass, fat-free mass and improve glucose homeostasis, and may reduce appetite, it does not appear to attenuate other adaptive responses to energy restriction or improve weight loss efficiency"

They also went on to say “Intermittent fasting thus represents a valid - albeit apparently not superior - option to continuous energy restriction for weight loss.”

But don’t form your opinion yet…I think you’ll be surprised by what other research has found (more on that later).

How long should I fast?

The numbers that come up most frequently in regards to fasting are 16, 18, 20, 24, and 36…and they all work pretty much the same way.

With that said, the standard seems to be about 16 hours, but fasting for upwards of 36 hours isn’t uncommon.

Determining how long you should fast is going to depend on a number of factors (e.g. school or work schedule, workout schedule, goals, preference, etc.)

Examples of Different Intermittent Fasting Schedules

A standard example of a 16 hour fast with an 8 hour “eating window” can be seen in the Lean Gains chart below. In this example, you’re fasting from 8pm to 12pm the following afternoon. You’re then “allowed” to consume calories from 12pm to 8pm, and repeat.

Another example of a 16 hour fast would be this: you’re fasting from 4pm to 8am the following morning, where your eating window begins, and then ends at 4pm.

Depending on a number of personal factors, the times you choose for fasting and feeding may need to be different. As long as the main principles are in order, (you’re fasting for 16 hours straight and eating only within your 8 hour window) you’re doing it right.

Fasting for 18-20 hours wouldn’t look much different than the examples above. For instance: extending the first example to an 18 hour fast would require that you either (a) fast a bit later (8pm-2pm), (b) cut your eating window off earlier (12pm-6pm), or (c) a mixture of both (e.g. fast from 7pm to 1pm while allowing meals within the hours of 1pm and 7pm).

The Benefits of Intermittent Fasting

Now that we have a clear understanding of what Intermittent Fasting is, how it works, and how to utilize it, it’s time we talk about the real reason people gravitate to it.

Check out this comment that was recently made on my YouTube channel under a video I did on Bulking Up with Intermittent Fasting:

Benefit #1 – Increased Insulin Sensitivity

From this statement, the most important thing to look at is increased Insulin Sensitivity from fasted training. Which is something that there is plenty of research on. But it also makes sense, theoretically. Insulin’s main role is to shuttle nutrients into cells - it also reduces the breakdown of fatty acids – making it harder to burn dietary fat or body fat when insulin levels are elevated. In terms of burning fat, training fasted may a viable option.

But don’t get caught in the hype…

Practically speaking, training on an empty stomach, for most people, will inhibit performance. Decreased performance equates to less calories burned and more muscle lost. At the end of the day, it’s all about energy balance; if you can maintain a caloric deficit, you’ll lose fat. And despite the increased insulin sensitivity from fasted training, if you’re not in a caloric deficit, you’re not going to lose body fat.

If you’re like me, then training fasted doesn’t get in the way of your performance. In fact, it allows you to be more focused and can, potentially, allow you to train even more intensely; however, if you’re like the overwhelming majority of the population, training fasted might not feel too good. Ultimately, it all comes down to whether or not you can perform in a fasted state.

Benefit #2 – Anti-Aging

Fasting triggers autophagy, a physiological process that deals with cellular repair (and I’m not talking about your broken iPhone screen). This is mechanism behind the anti-aging through restricting your calorie intake.

[Tweet "Autophagy: the mechanism behind anti-aging can be triggered through intermittent fasting. "]

Benefit #3 – Growth Hormone Production

Studies like thisand this…suggest that the blood levels of growth hormone may increase as much as 5x.

Other benefits of Intermittent Fasting Include:

At this point, you’re probably convinced that Intermittent Fasting is, in fact, the end all be all for faster fat loss, overall health, and, potentially, the true fountain of youth.

I certainly wouldn’t argue too hard against that.

But consider this…

Fasting will not compensate for a shitty diet. Moreover, it will not compensate for a sedentary lifestyle. Thus making it exactly what it should be: a tool that can be used, but isn’t necessary.

Keep in mind that, for the most part, the benefits listed above have also been shown to be a result of exercising regularly, proper nutrition, or both.

Do I have to track calories on I.F.?

As stated before, fasting or not, the only way to lose fat is by eating in a caloric deficit. If you’re in a negative energy balance, you’ll lose weight, period.

To answer the question, however, it depends.

If you’re someone who is looking for an easy way to maintain or lose weight, achieve good health, or just drop a few pounds, then more than likely you’ll be in enough of a deficit by simply reducing your eating window. On the other hand, if you’re someone who weight trains regularly, and/or are looking to better your body composition in order to build (or maintain) muscle mass, drop body fat, and perhaps perform better in the gym; then I would recommend that you do track your intake.

Here’s why…

For fat loss, a calorie is a calorie; however, when we’re talking about performance and overall body composition, it’s a bit more complicated.

If the goal is to lose weight, then tracking calories and ensuring you’re in an energy deficit will suffice. But if the goal is to build (or maintain) muscle mass, get stronger, and burn fat, then we have to be a bit more strategic with the macronutrients that make up our caloric intake.


Maintaining muscle mass while restricting calories requires an adequate protein intake. Although the science is pretty clear that we won’t need more than about 0.8g per pound of bodyweight to build muscle, a study conducted by AUT University concluded that energy-restricted athletes will need a bit more. The consensus is that somewhere around 1-1.4g per pound of fat free mass is necessary to maintain muscle tissue. It’s also worth mentioning that someone who’s 12% bodyfat and has been restricting calories for 8 weeks may not need as much protein as an athlete who is 8% bodyfat and has been dieting twice as long.


The benefits of a healthy fat intake are seemingly endless, but in terms of building muscle and burning fat, a few of those benefits really stand out. For example: a healthy fat intake has been associated with decreased inflammation, faster muscle growth, increases in anabolic hormone levels, and reduced body fat mass,

I think it’s safe to say that getting in an adequate amount of fats is critical for achieving the desired body composition and performance.

And if you’re wondering, 0.3-0.4g per pound of bodyweight in fat intake will suffice.


When we are restricting calories, we become more susceptible to muscle loss. Thankfully, carbohydrates are muscle sparring and help preserve muscle mass. Not to mention, carbohydrates are converted into glucose, our body’s main source of energy, and ensuring we’re consuming enough carbs, daily, will aid in gym performance. Simply put, if we can maintain our strength, we can maintain our muscle mass.

And for those anti-carb Nazis out there, consider this: A study conducted at the University of Pennsylvania found that, after 12 weeks, a low carb diet and a high carb diet resulted in similar weight loss. No surprises there, though, since the laws of thermodynamics are pretty clear.

Tracking and Adjusting with Intermittent Fasting

Lastly, like anyone who’s been restricting calories for a prolonged period of time, you will eventually experience adaptive thermogenesis: the regulated production of heat in response to environmental changes in temperature and diet, resulting in metabolic inefficiency.

In layman’s terms, your metabolism will, at some point, adapt to the decrease in energy and thus adjustments will need to be made to achieve further fat loss. If you’re tracking your intake, this becomes as simple as cutting your carbohydrate intake by 25g and continuing on your journey.

On the other hand, if you’re expecting Intermittent Fasting to do the work without regard for energy balance, fasting or not, you’ll end up stuck.

[Tweet "If you’re expecting I.F. to do the work without regard for energy balance, you’ll end up stuck."]

What can I consume while I fast?

First we must understand what it means to be truly fasted.

While I could just tell you that being in a fasted state simply means that your stomach is empty, it’s not entirely true.

You see, when we eat food, insulin is released and its job is to transport nutrients into cells. Depending on how much food you’ve eaten, insulin levels can stay elevated for 3-6 hours, or more.

Once insulin is done doing its thing, it then drops to baseline. Once this occurs, your body is in a fasted state.

Now that we understand what a fasted state actually is, we can easily determine what is “allowed” during the fasting period.

intermittent fasting for fat loss

Water: This is probably a bit obvious, right? I am a huge advocate of drinking tons of water when fasting as it helps fill your stomach during this, potentially, painful period.

Black Coffee: Although there are calories in black coffee (about 2), there isn’t enough to take you out of a fasted state. That is of course unless you add sugar, creamer, or milk. Not a fan of plain black coffee? Use calorie-free artificial sweeteners to add flavor. And for anyone who’s confused as to why a fitness site would suggest artificial sweeteners, stop watching Netflix and start reading the scientific literature.

Tea: Whether you prefer it hot or cold, the choice is yours; however, like coffee, it must be consumed plain with the exception of calorie free sweeteners.

Diet Soda: If doctors can offer diabetic patients some diet soda, I feel comfortable adding this option to our list. Diet soda (when it’s calorie free) is another viable option for curbing hunger while fasting.

Calorie Free Energy Drinks: Like most things in our diet, moderation is key…and although it may not be a good idea to consume energy drinks, daily, having one every once in a while won’t hurt you.

Do I have to train fasted with IF?

Intermittent fasting has all to do with eating patterns and nothing to do with training. Although there are some slight fat burning benefits to training fasted, energy balance and performance are most important.

Ultimately, go with (1) what fits your schedule and allows for the greatest adherence, and (2) when you feel best and most primed in the gym.

It’s also worth mentioning that when it comes to weight training, the majority of trainees will perform better when they’ve had carbohydrates before lifting.

Although plenty of people, including myself, have reported increased focus and performance when training fasted, it’s something you’ll have to try for at least a few weeks before you can determine what works best for you.

Should I do IF?

Intermittent fasting is no doubt a powerful weight loss tool. But at the end of the day, it’s just that…a tool. Like anything else, there are pros and cons to this approach and it’s up to you to decide whether or not the pros outweigh the cons.

Personally, the focus I get from drinking coffee in a fasted state is more than enough of a benefit for me to use it, especially when the goal is to eat less. But I’m also, in some ways, an outlier who’s able to deadlift 405lbs for 6 reps on a completely empty stomach.

If you’re having trouble staying within your daily caloric intake, then perhaps reducing your feeding window could be the answer.

If you’re having 6 small meals, daily, and find yourself still hungry after each meal, then IF can be the solution you’re looking for. By reducing the timeframe in which you’re allowed food, you’re also reducing the number of meals you’re having. Less meals equal bigger servings, and bigger servings may be the difference between adhering and binging.

For example: if my goal was 2000kcal and I had 13 hours to meet it, I’d probably get there in 8 and end up trying to fend off hunger for the next 5. Not to mention, because I am starving, getting to sleep isn’t going to be fun…or easy. On the other hand, if I squeezed those 2000kcal, strategically into my day by pushing breakfast back a few hours, not only will I be allowing myself more variety in my food choices, but I won’t have to go to bed listening to my stomach rumbling.


I love intermittent fasting, but I have no bias.

At the end of the day, if you want to burn fat and maintain muscle mass, you have to do 3 things:

First, you must eat less energy than you expend. Second, you’ve got to make sure you’re getting enough protein to preserve muscle, enough fats to maintain healthy hormone levels, and enough carbs to perform in the gym. And lastly, you’ve got to maintain your strength – use it or lose it, my friend.

If fasting helps and/or allows you to do those 3 things, then go for it. If not, then don’t…simple as that!

Interested in building muscle with Intermittent Fasting? Check this out: The Truth About Intermittent Fasting for Muscle Gain

Looking for a simple fat-loss solution using Intermittent Fasting? Download my free guide: 21 Day Fast Abs.

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