| | Intermittent Fasting and the Power Athlete

Author / Leah Kay

It seems to be all the rage now, with online health coaches and internet fitness models claiming intermittent fasting can accomplish everything from getting you 6 pack abs to curing disease. And, if you pair it with a ketogenic diet, they say you will literally grow a red cape out of your traps and become Superman! A quick but soul crushing search of instagram shows over 900,000 posts with #intermittentfasting, which could leave anyone wondering if they’re somehow missing the boat on the greatest thing since sliced bread…errr cloud bread. But even with all that hype, is intermittent fasting really the right path to take as a hard-charging, muscle-building Power Athlete?

Intermittent fasting, or IF, is the practice of reducing your window of caloric consumption; there are multiple ways to accomplish this, but the most popular methods include periodic 24 hour fasts such as alternate-day fasting, or the 5:2 method, where you fast for 24 hrs, 2 days per week. But, many in the athletic community tend to lean towards eating every single day and simply compressing their eating window to anywhere from 8-10 hours. This approach means you’d fast for anywhere from 14-16 hours per day, every day. So, basically the Hunger Games without any small children hunting you.

The first question you have to ask yourself when considering IF is: What are you training for? What are your goals? If your goals in training are solely centered around fat loss, or if you are suffering from metabolic issues like insulin resistance, then IF might very well be a viable option for you.

With typical intermittent fasting, most people end up reducing their total caloric intake for the day without really thinking about it, which makes sense; if you’ve got less hours to eat, you’re probably going to take in less calories. Unless of course you’re like Rod Farva, and are majorly skilled at shoveling food down your gullet past the point of fullness.  However, if you’re not a movie character and have a normal appetite, the IF approach can create a reduction in overall caloric intake, which in turn can result in a loss of fat tissue.

But, if caloric restriction is the reason behind the weight loss success, can we get the same results by simply maintaining a slight caloric deficit every day? Surprisingly, not always! Multiple studies have shown that uniform caloric restriction can lead to a drop in body fat, but may also lead to a drop in lean muscle mass. In contrast, an intermittent approach had the benefits of reduced body fat but avoided the loss of muscle tissue. Whoa. Seems like we dodged a bullet there and IF is starting to sound pretty great. Maybe we should all be intermittent fasting, right? Not so fast. Remember earlier, when we stated that identifying goals for training was the first step in determining if fasting was a viable option? If packing on lean tissue and getting stronger are at the top of your goals sheet, you may want to rethink this approach.

While intermittent fasting may allow you to lose body fat and maintain lean mass, studies have shown that it falls way behind when it comes to actually adding lean tissue.  One particular study compared active men who were currently not strength training, separating them into an IF group and a control group that ate whenever they wanted to; both of these groups were then subsequently placed on a full body strength training program 3 days per week. The IF group lost 0.5kg of fat, but had no changes in lean muscle mass. Meanwhile, the control group gained 0.4kg of fat, but also gained an additional 2.3 kg of muscle! Even though neither group was instructed on amounts of calories to consume, the IF group, because of their shortened eating window, ate less calories per day. This reduction in calories definitely was not conducive to packing on muscles.

Another study done on male bodybuilders found that an 8 week IF protocol in which participants reduced their eating window to 8 hours resulted in lower testosterone and lower IGF-1. Yikes! Bad news for anybody that was looking for a one-way ticket to Jacked Street!

There’s also concern with intermittent fasting if athletic performance is your primary goal; some studies have shown decreases in anaerobic and aerobic performance in elite male judo athletes when they were put on an IF approach to eating, while other have shown that IF can lead to decreases in performance in middle distance runners, and decreased repeated sprint performance in trained athletes.

So let’s get back to our original question. What are training for? If your goals are purely aesthetic or fat loss related, then IF might be a viable option for you. On the other hand, if you’re looking to increase strength, muscle size, and athletic performance, then intermittent fasting is likely not the optimal approach that’s going to lead you to where you want to be.

Nutrition is anything but a one-size-fits-all approach, so if you’re still confused about what will work the best for you, check out our personalized nutrition programs and get one step closer to smashing your goals!


Brisswalter, J., et al. Effects of Ramadan intermittent fasting on middle-distance running performance in well-trained runners. Clinical Journal of Sports Medicine. 2011. 21(422).

Cherif, A., et al. Three days of intermittent fasting: repeated-sprint performance decreased by vertical-stiffness impairment. International Journal of Sports Physiology and Performance. 2017 12(287).

Moro, T, et al. Effects of eight weeks of time restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation and cardiovascular risk factors in resistance-trained males. Journal of Translational Medicine. 2016 14(290).

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Leah Kay

Former collegiate volleyball player and 7 year competitive CrossFitter. 6x CF regional qualifier and 1x CF Games qualifier. Began coaching CrossFit in 2009 while working towards a Bachelor's in Nursing. Studied functional medicine through the American Academy of Anti-Aging in 2013 with specific emphasis on nutrition and hormone regulation. Continues to blend love of coaching and wellness as Head Trainer and Co-Owner of CrossFit Katy and Functional Nutritionist at Specialty Healthcare and Wellness in Houston, TX.


  1. Mark on April 7, 2018 at 7:57 am

    Love it. Anyone interested definitely needs to try it on themselves. My body responded very well, and performance has stayed strong (not training for anything specific like competition, just my personal data). My training partner gets weak on IF and Keto. He loves the brain effect, but it doesn’t make him strong.

  2. Amanda on August 31, 2018 at 5:47 am

    Love this read!!! And agree–your food goals must align with your training goals!

  3. Andrea Lattarulo on March 1, 2019 at 12:02 pm

    I think there might be confounding factors here as IF per se does not involve reducing caloric intake and therefore, a study which confronts ad libitum diets vs intermittent fasting where the purpose is to build muscle is undoubtedly biased if it does not account for lost calories.
    When you confront an IF and an ad libitum diet paired up for total calories and macro nutrient split then it turns out that if actually promotes HGH and testosterone, at least in mice.
    It is still all to be definitively cleared, but beware of biases.

  4. John williamson on April 21, 2021 at 7:31 pm

    This is not true at all, I am a professional BJJ competitor and I do 16:8 and definetly have seen and increase in energy and performance. You get ripped much faster but my goal is not packing muscles like a bodybuilder.
    You should really do some more research on this

    • John on April 21, 2021 at 7:41 pm

      Now you are spouting bro-science. If you actually read all the research comparing fasting with daily caloric loads you would understand that fasting is just a cool way to caloric restrict. There is no magic and getting ripped faster just means you are consuming less calories over the day. In the countless studies I have read, when daily total calories were constant, regardless of the feed window, results were consistent. Again, fasting isnt “magic”. I agree that going into competition in a fasted state puts you on a high alert and makes you more lucid. There is a reason I played the majority of the my NFL games in a fasted state. I felt more dangerous and less tired compared to when I eat. But make no mistake, fasting isnt magic…you should do more research on this.

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