Intermittent Fasting for Athletes

The evidence for intermittent fasting being useful, or at the very least effective, for physique competitors is compelling.

But what if you aren’t a physique competitor?

After all, physique is different than performance.

And the reality is that most everyone high on fasting is a fitness professional, most of which are only concerned about looking good.

But what about those of us that are…a little more?

What about someone like myself, that lifts, tricks, and plays recreational sports? What about the days when I lift early and play late?

In other words, what if your life isn’t optimized solely for weight-training workouts? And what about life beyond the barbell?

Fasting for weight-training is all well and good, but we’re talking about performance here. Can fasters still perform at a high level?


Before diving into any research or practical experience, know that the word “fast” is being generalized here. There are many fasting schemes, like Martin Berkhan’s, Brad Pilon’s, and Ori Hofmekler’s.

To do my best at generalizing, I focused on the extremes. For instance, seeing no performance impairment after a 3.5 day fast makes it easier to predict shorter duration fast effects.


When it comes to performance and intermittent fasting, we lucked out. There’s a host of athlete specific fasting research thanks to the religious observance of Ramadan.

During Ramadan, participants fast from both food and drink from sun-up to sun-down. So it’s tremendously hellish compared to most of our comfy fasting experiments that have us sipping on coffee and chugging water.

Keep that mind: these athletes are going without food and drink. It’s safe to say that they would undoubtedly perform better with some kind of hydration.


No food or drink for hours upon hours? Performance has to drop. Right?

I would think so too.

But this just isn’t the case.

Many studies (see end of post) and stories show athletes of all shapes and sizes doing just fine without both food and drink. But there are also some downsides.

Here’s a quick rundown:

  • Performance, for the most part, is maintained.
  • Performance never increased as a result of fasting.
  • During Ramadan, few athletes eat enough to match caloric demands.
  • But when body weight is lost, it’s mostly fat, not muscle mass.
  • Huge feasts before bedtime can negatively affect sleep.
  • Experienced Ramadan athletes handle the fast better and have performances to show for it.
  • Anticipatory feelings towards a meal can disturb performance.


It’s safe to say that performance—for the most part—can be maintained on an empty stomach.

Overall, it seems athletes with stable mindsets do the best. So craving food and obsessing over hunger is foregone failure.

Anyone that ventures into intermittent fasting knows that it takes time to get used to new eating patterns. And yet these athletes are suddenly thrown into a situation without both food and drink for 12-or-so hours. So their maintenance of performance markers is impressive. The big take home here is that hunger is  apparently what you make of it.


More so than specific nutritional demands, the main consideration for an athlete and fasting is living at the extremes.

What I mean by this is that you’re either hungry, or you’re full. A hungry athlete isn’t going to perform well unless they are mentally conditioned to accept hunger as an arbitrary feeling. Most people, however, associate hunger with depletion.

But the other side might even be worse—performing on a full stomach. Big meals increase parasympathetic nervous system activation. Think of the Thanksgiving sleepy effect. Not good.


The ironic part about intermittent fasting and performance is that if you’re considering it (or even experimenting with it), you likely have a better diet than most professional athletes. (Who usually eat garbage. To the left is Michael Phelps's “diet.”)

To decide whether or not fasting is for you, and to see how to arrange it around your activities, first ask yourself if you thrive or dive on hunger?

If you can manage hunger fine, the Ramadan studies show that most performance markers can be maintained.

Here are some suggestions:

  • Have your biggest meal later in the day, after any strenuous activity. Don’t worry about eating late, it might even benefit you. But don’t overly jam calories down your throat before hitting the pillow, as it can funk up sleep.
  • Don’t eat any big meals 6-8 hours before activity.
  • Follow a general template of scheduled meal times, but don’t be overly anal about it. Late games might mean eating a larger meal at 10-11PM. That’s OK, even if your last meal should be at 8ish.
  • If you’re doing anything strenuous for over an hour, think about getting something small in your stomach beforehand. Not so close to the activity, but not so far either. Just make sure it’s small enough to feel “neutral.” Don’t be starved. Don’t be stuffed.
  • This is more of a personal anecdote, but a heavy dose of carbohydrates prior to activity never ends well. On almost every experimental trial, carbohydrates (outside of something small like fruit), resulted in a crash and burn. So if you lift early and play late, save the big carbohydrate meal for later (not post-workout).
  • If you’re having trouble fitting in the calories, be sure to optimize your “off days” when nothing is planned. So maybe a few hectic days can't be as “structured” as you prefer, and you can't eat enough and adhere to fasting principles. Just take the hit. But fill up on the days that allow for more structure.
  • If you want to carb cycle, be mindful of what kind of athlete you are and what your macro demands are.


The big takeaway here is that hunger isn't going to kill your performance. Every day, collegiate and professional athlete's train at 6AM. The vast majority don't eat anything before their training. Most of them are still half asleep, actually.

When your feeding period starts, eat or or two smaller meals. Don't get full. Don't be starved. (Unless you can mentally tame hunger because, really, performance won't take much of a hit.)  Save your big meal for after any practice, games, or activity.

Do you have any experience with fasting and activity outside of weight-training? I'd love to hear your opinion, so post it in the comments. I'll see you there.


1. The effect of time-of-day and Ramadan fasting on anaerobic performances.

Findings: Before Ramadan, athlete’s had better night performances. During Ramadan, peak power dropped at night, but still matched morning performances. Perceived feeling of fatigue increased at night.

2. Subjective Perception of Sports Performance, Training, Sleep and Dietary Patterns of Malaysian Junior Muslim Athletes during Ramadan Intermittent Fasting.

Findings: Opinions all over the place. Half of participants said Ramadan had no effect. Over half said they were tired during the day. Only 40% were able to maintain caloric intake.

Thoughts: Maybe ones that reported fatigue couldn’t maintain intake?

3. Effect of ramadan fasting on body composition and physical performance in female athletes.

Findings: Most athlete’s couldn’t consume enough calories, bodyweight dropped. But there minimal to no drop in performance. Average deficit around 500 calories.

4. Effects of fasting during ramadan month on cognitive function in muslim athletes.

Findings: Performances requiring sustained rapid responses decreased in evening. Performances not dependant on speed stayed the same.

5. Ramadan and Its Effect on Fuel Selection during Exercise and Following Exercise Training.

Findings: “Separately, a single bout of endurance exercise places similar metabolic stress on the body as fasting since the exercising muscle must reduce its use of carbohydrate and utilize lipid more readily as exercise progresses. Not surprisingly therefore, adaptations in muscle to repeated bouts of endurance exercise (endurance training) are similar to those seen with repeated fasting/refeeding.”

6. Temporal Patterns of Subjective Experiences and Self-Regulation during Ramadan Fasting among Elite Archers: A Qualitative Analysis.

Findings: “Overall patterns revealed that experiences associated with physical, emotional, behavioral, and spiritual dimensions dominated in the first phase of fasting, while the mental dimension surfaced increasingly in the latter phase of fasting.”

7. Investigating Two Different Training Time Frames during Ramadan Fasting.

Findings: No difference in performance. But bodyweight dropped.

8. Effect of Ramadan intermittent fasting on aerobic and anaerobic performance and perception of fatigue in male elite judo athletes.

Findings: Fasting didn’t affect aerobic and alactic anaerobic performance. Anaerobic lactic suffered a bit.

9. Effects of Ramadan fasting on 60 min of endurance running performance in moderately trained men.

Findings: Didn’t affect performance.

10. Effects of Ramadan intermittent fasting on sports performance and training: a review.

Findings: “Whereas subjective feelings of fatigue and other mood indicators are often cited as implying additional stress on the athlete throughout Ramadan, most studies show these measures may not be reflected in decreases in performance. The development and early implementation of sensible eating and sleeping strategies can greatly alleviate the disruptions to training and competitiveness, thus allowing the athlete to perform at a high level while undertaking the religious intermittent fast.”

11. Intermittent fasting improves functional recovery after rat thoracic contusion spinal cord injury.

Findings: Perhaps intermittent fasting can enhance recovery?

12. Effects of Ramadan intermittent fasting on middle-distance running performance in well-trained runners.

Findings: “At the end of Ramadan fasting, a decrease in MVC was observed (-3.2%; P < 0.00001; η, 0.80), associated with an increase in the time constant of oxygen kinetics (+51%; P < 0.00007; η, 0.72) and a decrease in performance (-5%; P < 0.0007; η, 0.51). No effect was observed on running efficiency or maximal aerobic power.”

13. Effects of Ramadan fasting on physical performance and metabolic, hormonal, and inflammatory parameters in middle-distance runners.

Findings: Hormones mostly stayed the same through Ramadan, but there were some sleep disturbances and increased adrenaline overall.

14. The influence of Ramadan on physical performance measures in young Muslim footballers.

Findings: Zero performance effects.

15. Precompetition taper and nutritional strategies: special reference to training during Ramadan intermittent fast.

Findings: Experienced athletes are able to maintain performance.

16. Effect of Ramadan fasting on some biochemical and haematological parameters in Tunisian youth soccer players undertaking their usual training and competition schedule.

Findings: Zero effects.

17. Effect of Ramadan fasting on fuel oxidation during exercise in trained male rugby players.

Findings: Caloric intake reduced. There was more fat used as a fuel substrate and lower body fat levels found after Ramadan.

18. Impact of Ramadan on physical performance in professional soccer players.

Findings: Decreased performance. But what’s interesting is that players thought there would be.

19. Lipid Profiles of Judo Athletes during Ramadan.

Findings: Reduced body fat levels and able to maintain training load.

Trying to lose fat, build muscle, and build a body you’re proud of?

Maybe you’re a little lost right now.

Maybe you don’t have much motivation.

Maybe you don’t what program or diet to use.

I don’t know…

But what I do know is this:

Everything you need is inside of you.

You’re capable of more than know.

You just have to open your eyes.

My weekly column can help.

Just a small little honest note from me sent every Sunday.

Unless I’m hungover.

And then it comes Monday.

What I’m trying to say is that it’ll come Monday.

(These weekly columns don’t get posted to the site.)

Comments on this entry are closed.

  • Niko - no eXcuse fitness May 18, 2012, 3:10 am

    I regularly complete crossfit sessions in a fasted state. To be honest I don’t feel any difference in my performance. During these sessions I routinely wear a heart rate monitor and can see no difference in my heart rate, times or calories burnt. My hope is training in a fasted state will result in greater oxidisation of fat, obviously leading to fat loss.

    • Anthony May 18, 2012, 2:17 pm

      The research tends to say so. Thanks for the anecdote.

  • Freddie May 18, 2012, 4:34 am

    I have been fasting for about a year now and love it. One of the best benefits has been able to maintain a really lean bodyweight without any hassles, plus i just feel amazing not always worrying about food. I’m a big fan of Jason Ferruggia’s Renegade Diet

    • Anthony May 18, 2012, 2:18 pm

      Thanks for chiming in, Freddie.

  • yannick noah May 18, 2012, 1:33 pm

    Great post ill have less doubts and worries in training during ramadhan.For me, in ramadhan the biggest challenge is hydration. Malaysia is hot and because i couldnt consume water then that will be the challenge.What i would do is usually in ramadhan i will cut down my training intensity, frequency, and volume. Usually i when it is near to sun down so my break-fast would be my postworkout meal.Or i would train at night.but training would be quite a hassle because muslims would go to the mosque and have prayers for ramadhan.

    All in all, i am not sure if ramadhan fasting per se did have a negative impact on my performance during training. I have tried other intermittent fasting methods like 16/8 and the warrior diet and i find that my challenge is not so much of hunger, but hydration.Because i can learn to thrive without food but not water.This goes to training and outside training.Well i could be wrong as for all i know this is all just in my head haha.

    However i have one question.some intermittent fasting methods require bcaa intakes before training. with the absence of bcaa intake during ramadhan and as the findings would state that it does not negate performance, where does the value of consuming bcaa before training while in a fasted state come in then?

    • Anthony May 18, 2012, 2:21 pm

      That’s a good question, Yannick. BCAAs have been shown to benefit protein synthesis because they get digested quickly. This is the whole performance vs. physique thing.

      I will say, however, it’s been a good year or so since I took any BCAAs. I would take them if I had them. But I’m doing just fine without them.

  • yannick noah May 18, 2012, 1:38 pm

    *Usually i train when it is near to sun down so my break-fast would be my postworkout meal.Or i would train at night.but training at night would be quite a hassle because muslims would go to the mosque and have prayers for ramadhan

  • bryan boon May 18, 2012, 11:05 pm

    great post. have been doing martin’s 16/8 for about two weeks and felt no drop off in energy. i have dropped a few pounds and am amazed at the simplicity. march 1st was at 221, so dropped all starches and most sugars that month; lost 12. second month dropped all crystal light; lost 9 more. started fasting 2.5 weeks ago; lost 5 more. went from 221 to 196 and still losing. it sure as crap was never this easy on a bodybuilding diet!
    have also found that after teaching trx or spin at 0600 i can still get away with no food until noon…

    • Anthony May 19, 2012, 11:06 pm

      Sweet, Bryan. And thanks for sharing your insights. Really appreciate and love it when people are willing to give their own stories!

      Glad you’re having success. How far do you want to drop?

  • Kasey May 21, 2012, 3:33 pm

    I really enjoy the 16/8 method of fasting, but being a competitive (collegiate and otherwise) golfer, I’ve been kind of playing around with different things. I almost always walk and carry my clubs and usually play in the morning during my fasting times. I have been weary about playing without anything in my stomach (usually will have something light or some BCAA), but tried it for the first time last week and saw no ill effects. Walked 18 holes carrying the clubs and played just fine. I need to experiment a little more with it before I’d bust it out in competition, but attempt was a success. What do you think of fasted during competition?

    • Anthony May 21, 2012, 9:54 pm

      I’d make sure you develop some sort of routine first. For instance, if you’ve been going fasted for six months and playing in the AM, the competition better be in the AM. If it’s in the PM or something, you don’t want a fit of hunger to hit you out of no where and disrupt your play. By the same token, you don’t want to eat and then be stuffed during competition as that can whack you as well.

      So you want to try to have a “routine” for your competitions. The best you replicate this routine, the better you will perform.

      It would be interesting to see the fasting difference though. Golf shouldn’t be an issue though, even though matches can extend rather long. Might be beneficial to have some fruit and bcaas or whey on hand “just in case” or something. Just to kick hunger, not really provide a nutritional kick.

  • Crista May 21, 2012, 7:38 pm

    Great review! I’m a dancer and I workout 1-2 hours during the day and then have shows at night until 3am. I’m in good shape but looking to hit some stubborn fat on my thighs and just lean down. I want a way of eating for life to keep me leaner then most due to my profession. Any ideas or tips for fasting with my schedule?

    • Anthony May 21, 2012, 9:59 pm

      That’s a toughie, Crista. Especially without knowing what you currently eat like and whatnot. How do you deal with hunger? That’s the first question. And how early are your practices? And how intense?

      A lot of variables here.

  • Dave May 21, 2012, 7:49 pm

    I’ve been trying the leangains thing for the last few weeks and just find it really easy to implement. Not noticed any drop off in training. Rugby training on an evening has been fine, but i generally dont lift on days that i have practice, so havent had to think about juggling those two. I normally lift fasted between 10 and 12 and then feed after. rugby is at 7 so i normally have 1 or 2 small meals at 1 and 5 then a big meal after training. Maintaining bodyweight and no drop off in performance. Definately think i look more muscular and leaner even though its only been a few weeks!

    • Anthony May 21, 2012, 10:00 pm

      Nice, Dave. Thanks for the reply, really. Hugely appreciate it.

      Quick question: what are the small meals like before your practices? Foods, and whatnot?

      • Dave May 22, 2012, 12:33 pm

        At about 1 it’ll just be a bit of protein and maybe a few carbs, so veggie omlet or a chicken salad wrap (home made). and then later on just a snack, a piece of fruit and half a shake or a few oatcakes with a bit of peanut butter and half a shake. like you said, just something so im not starving.
        Might knock back a few BCAA tabs right before but i think thats more for piece of mind than actually affecting performance.

        • Anthony May 23, 2012, 12:43 pm

          Little snacks, nice. That’s what I would have to do too. Big meals would be barf-tastic.

  • Joe February 6, 2013, 4:37 pm

    Thanks for your informative and interseting article. I am trying to slim down and tone up for the next ski season with an intermitant fasting 5:2 diet! This is just recreational! I’m not an elete athlete by any stretch, although reasonably fit! The diet allows 600 calories total on a fast day! I eat no breakfast, 1 carrot and 1 apple for lunch and then tea is baked fish with cous cous and steamed green veg (total 525 calories!) or something similar!

    Any how! I have noticed my performance in the gym in the evening a day after a fast day is significantely impaired! For example I can only do a fraction or normal activity on the stepper machine! I seem to feel a bit tired a lack motivation as well! (so psychological / physiological I’m not sure!) I wonder the reason for this. Perhaps the glycogen stores in the legs are somewhat depleted and this is not replaced by the next day!

    Interesting your studies do not find this at all.



    • Anthony February 7, 2013, 7:42 pm

      I don’t know enough.

      Are you saying you train the day after a fast? I think you are but you didn’t tell me if you eat anything that day after and before training.

      Regardless, you should get off the stepper. You can make better use of your time.

      If you aren’t eating, it’s probably your liver glycogen that’s giving you fits.

  • Anon August 23, 2013, 2:50 am

    Hi anthony… Im looking for performance and do a deficit for 1 month. My training is in the am (weights mod-intense) and martial arts in the afternoon. My question is, since more data sugests that i should do pre wo for performance, do you recomend me eating breakfast? I normally fast 16/8 and im used to training with bcaa on an empty stomach.
    I train 8 am..
    Thank you in advance

    • Anthony August 26, 2013, 8:35 pm


  • Oli September 9, 2013, 6:30 pm

    You mention that no one improved while fasting. Any reason why ? Might be due to short studies or whatnot, but I can’t think of a reason why I should maintain performance but don’t improve.

    • Anthony September 10, 2013, 3:57 pm

      Ramadan is a different beast than intermittent fasting, remember that. You’re taking people and radically changing their lifestyle, so it’s not surprise that they didn’t tremendously boost their performance.

      Also, maintaining is a bunch easier than improving.

  • Lando September 19, 2013, 6:13 am

    I’m a professional mma fighter, training 2x a day, 5-6 days a week, and have been doing miyakis intermittent feast, along with a 24 hour fast on sundays for well over a year now. And I feel amazing everyday.
    Check out my series I do for vice.

  • Valerie December 5, 2013, 12:12 pm

    Hi Anthony, great information. I have been doing leangains for almost one year while weight training at 6:30 PM and have lost 25 lbs, all body fat!!! So excited about that although I started weight training at 4:00 AM so now my eating is all different. I work from 7:45 AM and off at 5:00PM. I have been fasting
    from 8:30PM -12:30 PM.
    I can’t figure out when I should eat now. I know how important it is to eat after training. Please help. Thank you, Valerie

    • Anthony December 12, 2013, 2:22 am

      I don’t put much emphasis on PWO IMMEDIATE meals.

      If you eat at 4AM, I’d just snack on some vegetables or take some whey every once in a while until you start eating. Sometimes life makes us live less than optimally.

  • Tom Edwards December 13, 2013, 3:49 am

    In summer break in college I was a mover, weight trained after work and did the Ori Warrior Diet. The next summer was the same except for not doing that diet. My strength gains were slow and consistent while on the Warrior Diet. But I never had enough energy to train endurance and had some embarrassingly bad performances in some wrestling matches because of that. The summer that I stuffed my face, I had initially much higher strength and mass gains. But they stopped and actually regressed when I got too fat. I was also trying a strength program that emphasized taking a lot of days off. I think after a while that program just stopped working for me. But around the end of summer I when I wanted to focus on conditioning I was able to train that much harder even though I was fatter.

    • Anthony December 17, 2013, 1:39 am

      Thanks for sharing your experiences.

  • Kimberley January 15, 2014, 4:09 pm

    Hello! Your site is great. Thanks for the info! I am a triathlete – 2 performance sessions per day. I’ve had some fasting experience before & wanted to try IF for several reasons: 1-I have mild colitis & feel better on an empty stomach , 2- I’ve put on about 5 pounds during the off season to 132 & 3- I am a busy mom who would love simpler meal times (not feeding me while trying to feed kids).
    Today would’ve been my 10th day. I’d been fasting from 10pm – about 1:30. My 2 training sessions are at 5:30 am & 9:30 am. Before IF my first session was fasted, and I’d have eggs & toast between sessions. Sports drink during 2nd session. 2nd meal within an hour of finishing session 2. Now, with IF, I’ve been having aminos pre & post workout 1 & bulletproof coffee post workout 1. To break fast @ 1:30: a big sandwich, crackers & cottage cheese for meal 1 with Chia seed + coconut water shake. Snacks: fruit, granola, fruit/veggie smoothie. Meal 2 – chicken or beef, veggies, rice. Meal 3: bowl of granola + cereal & coconut milk. I’ve been moderately hungry during my eating period; these past 3 days, not as hungry, but still eating.

    My 1st week of IF went fine. I was down to 128 lbs (some water im sure). No noticeable performance decrease. No sleep issues. Enjoyed the simplicity & increased focus during mornings. Something changed this week though. My weight has moved back to 132, and I’ve felt fatigued in the afternoon, but the kicker is I’ve felt terrible my last 3 workouts. Tuesday mornings swim, my perceived exertion was 9-10; usual PRE for this workout would be 7.5-8. Ame exact experience during this mornings run. I just could not hit my usual paces and I just wanted to stop. I’m not sick & this is the only change I’ve made.

    What are your thoughts? I really like the idea of IF. I do take 1 day off per week & could certainly do it that day. Any way I can try to work this differently that you see?? Thanks a bunch!

    • Anthony January 16, 2014, 8:28 pm

      IF isn’t for everyone, and it gets tough when you move away from training on a “normal” schedule. You don’t.

      I don’t think back to back training sessions on an empty stomach would go well, and that’s all I really have to say.


      • Kimberley January 17, 2014, 4:42 am

        Thanks! I felt much better today with light electrolyte drink (~100 calls) during my 5:30 am swim and a light breakfast (1 egg, 1 piece toast, coffee) afterward @ 7:30. Bike ride @ 9:30 with electrolyte + BCAA drink. Good energy; better power.

        I still delayed my big meal til 1pm but plenty of water + BCAA. Felt better this way. Then, 8 hours of regular eating/drinking. I know this isn’t IF because of my morning food, but back-loading most of my calories feels like a good modification for my double training session mornings. Thanks for your input!

        I also think I was having a really rough week hormonally & this may have played a role in my poor Tues-Wed. performance – especially since the week prior on IF was great all-around.

        • Anthony January 17, 2014, 11:49 pm

          There’s a lot of things that go into performance, no doubt. I think some of what Ori Hofmekler says might be of use to you. He usually recommends whey + some other things during an “underfeed” (not fast) window.

  • Cat July 2, 2015, 8:37 am

    I’m interested in this, as I am an endurance athlete (triathlon) and healthy eating coach.
    For some people (myself included) fasting seems to be the only way to manage weight-part psychological, part physical.
    However when I fast I personally feel better/look ‘better’ but I am concerned about recommending the practice to a) athletes who do long workouts and could ‘bonk’ or drop performance and b) people recovering from eating disorders or who struggle with food emotionally as I think it can encourage food-obsessive behaviours.
    What are your thoughts?

    • Anthony July 16, 2015, 11:58 pm

      IF isn’t for everyone. The two populations you listed would be some of the people I’d shy away from IF with.