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Intermittent Fasting (IF)

This Diet Technique Has Been Said to Promote Muscle Gain and Fat Loss, But How Does It Work?

Posted by Erica_Stibich - January 2nd, 2014

There has been a lot of buzz in the fitness community surrounding Intermittent Fasting (IF) and its fat loss and muscle gain benefits. Accounts of its results are everywhere with testimonials from fitness professionals to movie stars. But what is Intermittent Fasting and what is the theory behind it?

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First, Let’s Talk About How Intermittent Fasting Works.  

This dieting technique has not been thoroughly proven but preliminary trials suggest that by cutting or eliminating calorie intake for a period of time causes your body to dramatically deplete its glycogen stores. This in turn, directs the body towards using stored fat as its primary source of energy resulting in reduction of intramuscular fat stores or fat loss. So this is how fasting promotes fat loss, but how can cutting calories help muscle growth?

With a reduction in fat on your muscle tissue, your muscle cells become more sensitive and responsive to insulin. Insulin is a powerful anabolic hormone that promotes protein synthesis increasing muscle mass. This means that when you return to your regular diet, your body’s ability to take in all of those important nutrients is significantly enhanced causing your muscles to grow. Fasting also promotes Human Growth Hormone (HGH) production, another critical protein synthesis hormone.

So Intermittent Fasting seems like a powerful combination creating a snowball effect where your body loses fat causing it to become more sensitive to insulin, which helps you grow more muscle, which, in turn, increases metabolism, resulting in more fat loss and so on…

Now You Understand The Theory Behind IF, But How Is It Done?

Intermittent Fasting comes in many different forms. For the purpose of this article, let’s focus on two common variations.

5 – 2 Intermittent Fasting

The first one is known as the 5-2 IF. On the 5-2 IF, you dramatically reduce your caloric intake for 2 days out the week and then return to your regular diet for the remaining 5 days. The 2 fasting days do not have to be consecutive so you can intercalate with regular eating days. The general guideline is to eat a quarter of your regular calorie intake during the fasting days. For example, if your daily calorie goal is 2400 calories, you should then reduce your intake to 600 calories on your fasting days.

Many people have experimented with this format and attest to the results but, I have concerns. For two days every week, you are not meeting your macronutrient requirements. This has consequences. If your main goal is hypertrophy, it is pretty common knowledge that you need to consume high amounts of protein to support muscle repair and subsequent growth. This macro nutrient’s shortage might offset the benefits of fasting. What would be the benefit of making your cells more responsive to insulin, if you are not supplying adequate amounts of protein for protein synthesis in the first place? Also, your body is an incredibly smart machine and adapts to the conditions it encounters typically changing its processes to maintain its main bodily functions. When it detects that it is in a low nutrient state, it changes to “energy saving” mode. As result, energy levels drop and your workouts suffer. The bottom line is: I am not a proponent of any method or technique that doesn’t ensure adequate supply of macronutrients or that jeopardizes workout effectiveness or intensity.

16 – 8 Intermittent Fasting

The second variation entails a daily period of fasting with your meals condensed to a pre-determined window. A common scenario is to fast overnight for 16 hours with all the meals ingested within the remaining 8-hr window. In this case, you are still eating your daily goal of calories but eating them as larger meals within a shorter period of time. Ideally, you would have your biggest meal right after your workout with the calories tapering off as you approach the end of your window.  

Obviously, workout schedules are different for each individual so you would have to adapt your eating schedule to your daily routine. This method is my preferred one because you still consume your required amount of macronutrients while taking advantage of the fasting benefits. The fasting window can be varied but keep in mind that it takes 6 – 8 hours for your body to deplete its glycogen stores and switch to using fat as source of energy, so make sure you allow time for this process to happen.

If You Decide To Give IF a Try, Here Are A Few Tips To Help With The Fasting Process:

  • Start small and move towards a stricter fast schedule. A good start would be a 10-hr overnight fast and then progress to longer periods.

  • Drink plenty of water. It will help curb your appetite.

  • Take BCAAs (Branched Chain Amino Acids) during workouts to help with recovery and prevent muscle breakdown.

  • When not fasting, make sure your meals contain the appropriate macro ratios for your goal and focus on eating lean protein, complex carbs and good fats.

A Few Words Of Caution:

  • If you have a medical condition or are pregnant, make sure you consult with your doctor before attempting this technique.

  • Keep in mind that we are all different and what works for some might not be the best option for others. Fasting is not for everyone. Some people might not have any trouble controlling their appetite after the fasting period while others might end up on a binge eating feast after being on such a significant caloric deficit.

  • Fasting is not a requirement for getting big and lean. If this is not for you, don’t get discouraged. There are plenty of more traditional meal plans out there that will help you achieve your fitness goal.

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@scott_herman, @jmboiardi

I am digging this article back up. I have done the 16:8 in the past and it worked great and I believe I was in a little bit of a surplus. Anyway my schedule changed that but I have been eating in a deficit with slow results. I am back on IF but seem to be at a halt at 3 weeks in. Is eating on a deficit while doing IF too much of a shock?

Scott_Herman  Edit  Delete  Close

yeah that is it 100%!! see, this is why you have me :-D

Adawg38  Edit  Delete  Close

I really think I should of rechecked my Macros @scott_herman. I am only 100 calories below maintenance and I don't know how I got there. I thought I was 400 under. Maybe that was my problem? My cut was slow but makes sense, I was just worried 3 weeks into IF and my bf seems to be going nowhere, I also just wanted to be sure IF and a deficit wasn't too much at once. I need that 8%-10%!

Scott_Herman  Edit  Delete  Close

I don't think so.. but what is the wall you hit @adawg38?  Trying to cut up with the deficit?  Maybe your deficit isn't as big as you think it is?


I've asked this of several IF proponents and haven't gotten a straight answer yet. How are you not breaking your fast if you're taking BCAAs intra-workout? I've been doing it off and on (back on now) and it is a useful tool for maintenance.


Trying this out (started @ 9pm). Fun and interesting times for this 180# skinny-fat old man.


i really enjoyed this article Erica, i was thinking of trying this out today and see how it works, thanks again

FaithBramlett  Edit  Delete  Close

True! I totally forgot to add that... water helped me a lot. 

Scott_Herman  Edit  Delete  Close

water helps alot  BCAAs are good to help too!

FaithBramlett  Edit  Delete  Close

Silverfox!!! Keep on keeping on!! Your tummy will soon become used to it. Fasting works! Erica's article indeed was very informative. 


Great article babe!  This is going to help A LOT of people!


Nice article !


I have been doing the 16:8 fasting protocol for about 9-10 months and I am the leanest I have ever been.  IF is the real deal and it has been the best food intake modification regiment I have ever followed :-)

SavvvyD  Edit  Delete  Close

It totally works for me too. I was looking fluffy in the arms, so I readjusted my intake and started eating between 10-6, BAM! The extra fluff cut away. I was eating double what someone my height should be eating lol 

Erica_Stibich  Edit  Delete  Close

I agree with you! I also do the 16:8 protocol and it really works for me! I used to have a real hard time at night with other diets because I would get home from the gym starving and eat everything! I love that, this way, I start eating around 4 pm and I actually HAVE to eat at night! I loooove it!!!  


Works for me when I can stick to it 16-8 Being away from home, not able too do it

I've heard this term thrown around here and there before, so it's nice to finally see what all the fuss is about. I don't know if I'd want to deprive my body like that, but it does make some sense. While I may not do it, to each their own :) Great article, thanks.
Erica_Stibich  Edit  Delete  Close
Glad you like it!!! I have been researching the topic for a while because it is the buzz on all the fitness shows I go to! :)
Great! I did this for a month and I've lost around 15 lbs ..on your fasting day, avoid intense workout cuz I almost black out when I did and I needed to consume some sweets after just to recover. I am now back to high protein diet and I noticed that I am getting bigger a lot faster but I think it's in a good way.. meaning more definition and muscle bulk! :D Thanks for this article Erica! #HTH
Erica_Stibich  Edit  Delete  Close
So glad you like it!!!! I agree with avoiding the intense workout! I was doing the overnight fasting and every day woke up feeling so weak and depleted that there is no way I could workout! I had to wait until later in the day so I could get some nutrients in!!!! :)