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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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April 12, 2012

Why Fast? Part Five – Exercise

By Mark Sisson
176 Comments

In previous installments, I’ve discussed the powerful effect of fasting on weight loss, particularly with respect to adipose tissue. I’ve explained how intermittent bouts of going without food have been shown to increase cancer survival and resistance and improve patient and tumor response to chemotherapy, and I went over the considerable evidence suggesting that fasting can provide the life extending benefits of caloric restriction without the pain of restricting your calories day in, day out. And last week, I highlighted how fasting may have protective and therapeutic benefits to the brain.

As such you might be thinking that I only recommend fasting to the sedentary, the aged, and the infirm. Surely I wouldn’t go so far as to recommend to the active, the athletic, and the jacked that they engage in vigorous physical activity without having eaten a solid square meal beforehand – right? I mean, no good can come of a fasted training session, as the gym bros with the sweet ‘ceps are so quick to intone.

So, Sisson, what’s the deal? Can we exercise in the fasted state and live to tell the tale?

Yes. And there may even be benefits to doing it. There’s actually not a huge amount of literature on the subject out there, with the bulk of it studying Muslim subjects during Ramadan and getting mixed, sometimes negative results. I’m wary of using the negative results of the Ramadan training studies to color our opinion of fasted training for the population at large for three major reasons: first, Ramadan restricts daytime food and water intake during the fast. If you’re sedentary, you can probably get by without guzzling water, but if you’re an athlete, or even just someone who dabbles in a bit of lifting, some walking, and maybe a few sprints, your performance and results will suffer without adequate hydration. And I’d say a complete and utter absence of water during daylight qualifies as “inadequate hydration,” wouldn’t you?

Second, since eating and drinking are limited to pre-dawn and post-sunset hours, Ramadan often means sleep deprivation. Studies show that sleep onset occurs later than normal, sleep duration is lessened during the month (PDF), daytime sleepiness increases, and general performance of daytime tasks decreases. We’re already aware of the importance of sleep for general health, but inadequate sleep can also translate to poor athletic performance.

Third, the subjects in these studies most likely aren’t on a healthy Primal eating plan. Heck, they’re probably not on a conventionally healthy whole foods diet. While it would be nice to believe that these Ramadan fasters were feasting on fresh lamb, high quality extra virgin olive oil, extra-thick pastured labneh, grass-fed breadless shawarma, and pomegranate salads, they were likely eating the same junk that everyone in the industrialized world eats. And as such, they were probably poorly equipped to shift smoothly and easily to the fat based metabolism required by fasting. Sure, they switched over to burning their own body fat out of necessity and a sheer lack of calories, but it wasn’t the easy, seamless transition that Primal eaters typically enjoy at the drop of a hat. For the carb-addicted, fasting is mentally, physically, and spiritually taxing. For the fat-adapted, fasting often just happens. As we often say around here, we eat WHEN – When Hunger Ensues Naturally. For folks with easy access to the fat-burning switch, skipping a meal (or three) doesn’t ruin the day and preclude exercise.

Right off the bat, then, I’ll say this: don’t even consider fasting and training if you’re not going to hydrate, sleep, and become fat-adapted.

Now that we have those caveats out of the way, let’s look at some of the purported benefits of exercising in a fasted state, as shown in the literature:

Improved Insulin Sensitivity

Intermittent fasting improves insulin sensitivity, as I mentioned before in the fasting and weight loss post. A recent study found that this effect is heightened when combined with exercise (in this case four days of endurance training each week). By the end of the study, subjects who fasted had lower body weights (the only group not to gain weight), better body-wide glucose tolerance, and enhanced insulin sensitivity. Furthermore, only fasted training significantly improved muscular adaptations to training.

Improved Recovery from Endurance Exercise

Three weeks of overnight-fasted endurance cycling (with caloric restriction to boot) improved post-workout recovery, maintained lean mass, lowered fat mass, and maintained performance. There was unfortunately no control group, but this study does show that fasting doesn’t hurt (and it may help).

Another study suggested that fasted endurance training may quickly re-activate the muscle protein translation that was negated in athletes who had eaten carbohydrates before training.

Improved Recovery from Weight Training

A 2009 study found that subjects who lifted weights in a fasted state enjoyed a greater “intramyocellular anabolic response” to the post-workout meal. Levels of p70s6 kinase – a muscle protein synthesis signaling mechanism that acts like an “indicator” of muscle growth – one hour after a fasted workout doubled levels compared to one hour after a fed workout (in the same group). In other words, fasting boosted (physiological indicators of) post-workout muscle growth.

For a further look, check out Martin Berkhan’s take on the study. Also note his recommendation that 10 grams of BCAA (branch chain amino acids) taken before the workout should boost the enhancement without taking you “out of the fast.”

Improved Glycogen Repletion and Retention

What happens when you train in a low-glycogen state? If you’re used to running on full glycogen stores, your performance might take a hit when you have to shift toward a more oxidative, fat-based energy pathway. That’s understandable. Another thing that could happen is you learn to make do with less glycogen by, well, making do with less glycogen. This is elementary stuff, folks. Just like your muscles adapt to imposed stressors by getting stronger, your body adapts to low glycogen training by learning how to train under low-glycogen conditions, thus sparing glycogen for when it’s really needed and boosting performance when glycogen is actually available. It’s the classic “train low, race high” idea that I’ve discussed before. It’s the specific adaptation to imposed demand (SAID) principle, only in this case the “imposed demand” is a low-glycogen, low-food environment.

A recent study exemplifies this phenomenon, pitting a group of untrained, carb-fed cyclists against a group of untrained, overnight-fasted cyclists and comparing both groups’ muscle glycogen content and V02 max. Who won? The fasted group improved their V02 max by nearly 10% and their glycogen content by over 54%, while the fed group improved V02 max by just 2.5% and glycogen by a paltry 2.9%. Lesson? Don’t eat 1.5 grams/kg body weight in cereal-based carbs pre-workout, and definitely do not eat a delicious shake of waxy maize during your workout (unless you really really like cereal and corn starch slurries).

What do you notice? Fasting does not instantly imbue its adherents with super powers. It’s not supposed to. Improved performance during a given training session isn’t really the point of fasted training. The point of fasted training, as I see it, is to maintain performance while enjoying the metabolic benefits, like improved recovery, higher glycogen stores, better insulin sensitivity, and improved muscle response to exercise. The point is that fasted training won’t kill you, won’t eat your muscles, and it might even improve adaptation to exercise by forcing you to train in a “less optimal” state, which can boost performance down the line. The Olympian isn’t going to be well-served by doing the main event on an empty stomach, but he just might benefit from occasionally training on one.

Mind and Matter Matter

The success of your training, whether it be lifting heavy things, running, sprinting, rowing, cycling, or climbing, isn’t wholly dependent on your physical state. The amount of glycogen in your muscles and liver, the mobility of your tissues, the structural size of your muscle cells, the distribution of the fiber types within those muscle cells, the V02 max – these all matter and help decide the amount of weight you’re going to put up, the time you’re going to hit, the miles you’ll be able to check off, and the number of pullups you’ll complete, and fasting will obviously have an effect on these and other markers. But just as important is your mindset, your personal approach to fasted training.

Me, I like a good long hike in the morning with maybe just a cup of coffee in me. It gives me exactly the kind of steady energy I want without negatively impacting my performance (which doesn’t really matter on a pleasant hike) or my enjoyment (which does). However, I don’t like playing Ultimate Frisbee on an empty stomach. I can do it, but I feel like it impairs my performance – and when I play Ultimate I play to have fun and win (as PrimalCon attendees are soon to find out). As far as lifting goes, I’ll sometimes do it fasted, but I’m a big fan of fasting after a strength workout. I do so to milk the post-workout growth hormone surge and because I’m just not that hungry immediately afterward. If immediately stuffing one’s face was required for optimal gains after a workout, you’d think we’d all be ravenous after lifting heavy things, but we’re not. I can do sprinting on an empty stomach, but I hit the wall quicker (probably due to the depleted glycogen).

Don’t let the results of a study (or my words) dissuade you from doing something that seems to help you. If fasted resistance training has you hitting PRs (or at least feeling like you could if you wanted), keep doing it and disregard studies that suggest “THIS IS IMPOSSIBLE. YOUR GLYCOGEN-DEPLETED MUSCLES WILL SURELY DISSOLVE INTO THE ETHER.” If fasted resistance training has you lagging, eat something the next time and disregard studies that suggest “YOUR POST-WORKOUT MUSCLE PROTEIN SYNTHESIS AND INSULIN SENSITIVITY WILL SKYROCKET TO THE HEAVENS ABOVE.” In the long run, it may not matter. People have gotten in great shape eating six meals a day or just one.

Whatever you do, don’t fall prey to paralysis by over-analysis, as did one of the Worker Bees. This guy got way too deep in the fasting literature. He was reading PubMed articles, scouring online weightlifting forums for anecdotes about fasted training and running multiple self experiments with his eating and training. He become so enamored by the idea that working out in a fasted state would elicit superior metabolic and performance effects that he found himself unable to workout if he’d eaten anything at all. And it wasn’t a physical inability; it was a mental hang up. He became frozen, stuck and often unable to reap all these wonderful benefits he spent so much time reading about, all because he felt guilty working out if he’d had so much as a few pieces of beef jerky, a couple eggs, and a banana. Don’t be that guy. He has since seen the light and now realizes that something is better than nothing, that even “non-optimal” training can still be effective. But he wasted a lot of time getting there because he obsessed over studies performed on people who were not him which suggested some (often obscure) benefit to working out in a fasted state.

Do what works for you and if you find that fasted training qualifies, so be it. But don’t think it’s a requisite of Primal living. While I absolutely recommend that people play around with it, and most people find that Primal eating makes it easier, fasted training is not required.

What are your experiences with fasted training? Have you tried it? What benefits, if any, have you noticed? What about particular activities, like sprinting, lifting, or jogging – how do they respond to fasting?

Here’s the entire series for easy reference:

Why Fast? Part One – Weight Loss

Why Fast? Part Two – Cancer

Why Fast? Part Three – Longevity

Why Fast? Part Four – Brain Health

Why Fast? Part Five – Exercise

Why Fast? Part Six – Choosing a Method

Why Fast? Part Seven – Q&A

Dear Mark: Women and Intermittent Fasting

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176 Comments on "Why Fast? Part Five – Exercise"

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liberty1776
liberty1776
4 years 5 months ago

I find when I fast and do intensive physical work that I start off slow and then my energy builds. I feel light and good afterwards. I do drink water though.

edearl
edearl
4 years 5 months ago

Brilliant liberty1776! My exact thoughts. I had this experience during my “lunch” break today. I do try to eat within the first hour post-workout. By that point I have typically been fasting for 15-16 hours (since supper the night before.) Great stuff Mark!

Joseph Fetz
Joseph Fetz
4 years 5 months ago
I completely agree, Liberty 1776. I often will skip breakfast and go for a quick 20 mile ride on the bike. After about mile 5 my energy is so high that I am peddling like a maniac. Then, after I am done I am completely full of energy, and this often lasts till lunch. This is not to say that I get sluggish near lunchtime, only that the super-duper energy has subsided to only super energy. 😉 Also, I’ve found that when I do a 24 hour fast every now and then, that my energy levels are good and steady… Read more »
Matthew Caton
4 years 5 months ago
During a fast your body is already up-regulating catecholemines such as epinephrine, norepinephrine, and cortisol. When you train in a completely fasted state, your body pumps out even more more adrenaline, noradrenaline, and cortisol to release fatty acids and glycogen from fat cells and the liver, respectively. The effects of fasted training is almost always a light focused feeling. You really can’t beat the benefits of fasted training. Not only will you see the metabolic benefits, and increases in performance, but you can actually REVERSE AGING. I talk about this extensively on my website, The Fountain of Youth and Strength.… Read more »
Jonathan
Jonathan
4 years 5 months ago

That’s interesting as I’ve finally got into the habit for an all-day fast to work out at 5pm or so. I just bought a container of BCAA’s to try and get some extra boosts to muscle growth and haven’t tried it yet. What is the evidence for/against BCAA’s breaking the fast?

Matthew Caton
4 years 5 months ago
Well there are hardly enough studies to even really decisively conclude that fasted training is superior to fed training. I know there are no studies done, or coming in the near future, that analyze the differences between completely fasted training and training with BCAA, so we just have to use common sense. BCAA’s are extremely insulinogenic, and fasting is really defined as having low levels of insulin. So you jack insulin up with BCAA, you activate the mTOR pathway and you lose part of the benefits of autophagy. Not only this but the increased protein synthesis that occurs post-fasted workout,… Read more »
Jonathan
Jonathan
4 years 5 months ago

Ok that’s quite interesting and I didn’t realize that. Are the large GH spikes during fasting utilized when you finally break the fast for better growth response from muscles or does that all evaporate with the insulin reponse?

Nick Richardson
4 years 5 months ago

So Matthew,

If you were trying to achieve hypertrophy, would you train in a fasted state and not take BCAA’s and not eat for a few hours afterwards to increase GH? Or would you not be in a fasted state and take BCAA’s and then eat after? Or alternate between fasting and not fasting on workouts maybe?

p.s. I like the way you look at the primal thinking/way of living and combine it with physiological reasoning.

shane
shane
3 years 8 months ago

so are you saying that if i have been fasting I shouldn’t drink BCAA’s during my workout?

Tony
4 years 5 months ago

I agree. As an endurance cyclist, I was conditioned early on to train on an empty stomach; only consuming water during training rides. I’ve found my body adapted over the years. It has become efficient at utilising food – whether training or during recovery. I’ve also found maintaining my ideal body weight a breeze as a result of such conditioning Thanks Mark!

Jo
Jo
4 years 5 months ago

Thanks for the great post, and the link to the PDF, Mark.
I’m only going on my second week of eating this way and incorporating your fitness advice, and I am already feeling terrific results. In fact, I am Muslim, and one of the first things I thought about, once I started experiencing the lack of hunger when eating this way, was how much simpler Ramadan will be this summer. Yes, it will still be a challenge, due to fatigue and lack of sleep, but that carbohydrate-driven hunger doesn’t have to be a part of the equation. Brilliant.

Christina
Christina
4 years 5 months ago
I’ve had some experience with fasting and exercising and I’m still experimenting and trying to figure it out, but I’ll share my experiences so far and questions. First off, let me say that I had done 1 day fasts (from everything but water) prior to going primal (well, trying to be mostly primal…probably usually around 80%…sometimes much closer to 100, sometimes worse), and the difference is astounding. In the past going without anything but water for an entire day seemed like torture, so hungry, no energy, light-headed, etc. Now it’s no problem at all. Sure, I’ll get hungry, but I… Read more »
Matthew Caton
4 years 5 months ago

After around 12 hours of a light meal (600 calories) insulin will be at fasted levels and you will technically be in a fasted state.

If you were dehydrated that could have been the reason, but if you were fasting more than a few days, then didn’t do a large enough refeed, or if you didn’t eat enough protein during the refeed, then you probably had very low levels of leptin, and that could also explain your symptoms.

sdiguana
sdiguana
4 years 5 months ago
I recently ran an experiment based on this article series of fasting as 20 / 4 sequence, and i found that my mind was useless during the day (bad for maintaining gainful employment) and that in the evenings when i would eat, i’d end up with stomach aches and headaches (atypical for me… very rarely get either). Went at it for 3 weeks before i decided id push back to a 16/8 type fast, i’m testing it now, but i’ve only been at it a few days, so we’ll see what comes of it. (eaten paleo since mar 11, 12%… Read more »
Bruno
Bruno
4 years 5 months ago
Hi Sdiguana, I only eat two meals a day on most days, so I’m constantly on a 16/8 schedule, but I’m not anal about it. It’s been the best set up I’ve found so far. I supplement my mornings with coffee and never really go hungry. I recently started incorporating 2 – 24 hour fasts into the week too (Monday and Thursday) because… well.. because of all these Fasting articles. So I eat Sunday night, and then I fast on Monday, work out in the evening, and then feast. I added the Mon & Thurs fast just a couple of… Read more »
mkessler17
mkessler17
4 years 5 months ago

Hi Bruno,

I am doing the same exact schedule as you and appears to be working perfectly. Dropping fat like crazy and my strength is going off the charts. I need to buy more weights and new clothes! Thank goodness my food costs are down!

Gregg
Gregg
4 years 5 months ago

You are looking great!

liberty1776
liberty1776
4 years 5 months ago

Hunger and thirst are highly evolved feedback mechanisms, listen to them. Hungry? Then eat. Thirsty? Then drink. I do not pick my days or time period to fast, my body does. I just listen.

Joshua
Joshua
4 years 5 months ago

That’s great that you understand your body’s signals. Most of us though, until we’ve become fully fat-adapted and restore the default settings of insulin sensitivity and all that, and have fasted enough to remember what real hunger feels like, will confuse our body’s messages with cultural factors like time of day, boredom, and certain activities and days.

liberty1776
liberty1776
4 years 5 months ago

I echo the cultural factors, especially boredom. I use to do many detrimental things to my health when bored, like getting bombed on and then eating a whole pizza; which I ain’t gonna lie, it was pretty awesome! But now that I know the word for this behaviour I just say it to myself, “akrasia”. It has not failed me yet.

mars
mars
4 years 5 months ago

I agree with this. I don’t live by specific times to eat. I’m a pre-dawn runner and weightlifter, and I rarely eat before my runs or workouts. I’m just not hungry at 5:00 am. Unless I’m doing weekend long runs, I am fine running and working out on an empty stomach. I prefer it actually.

jake3_14
jake3_14
4 years 5 months ago

You can train your body’s appetite, to an extent. I took a leap of faith after reading leangains.com and did just that. Now, I “fast” 15-16 hrs./day, and my body gets hungry only at lunch and dinner times.

Daniel Wallen
4 years 5 months ago
Same experience here. I used to think I was seriously hungry every four hours–but it was only my head, and the fact that I obsessed over what the “best diet was” and based on the literature I had read, small frequent meals was the way to go. Then I started reading about fasting and gave it a shot–it was hard to eat so much in one sitting at first, but I quickly got used to it. I have more clarity at work; have better workouts (I used to sometimes end up with an upset stomach during training if I ate… Read more »
Joseph Fetz
Joseph Fetz
4 years 5 months ago
Liberty, that is actually how my very first fast started. I was at work and our first break came up. Usually I will have a small snack or a salad during break, but I simply didn’t feel hungry. So, I decided to wait until lunch, but when it came around I still wasn’t hungry. I didn’t eat until around noon the next day when my hunger mechanism said, “ok, time to eat”. That entire time I felt awesome. I try to get in a 24 hour fast at least twice a month, but I don’t schedule it, I just wait… Read more »
Naomi Most
4 years 5 months ago

You don’t need to fast that long to get the benefits of fasting. And there is evidence that the hormonal state that produces the benefits of fasting comes from abstaining from CARBS (and excess protein), not abstaining from food entirely.

So effectively that means you can eat little bits of energy-sustaining fat (like coconut oil — try adding 1 Tbsp to coffee — produces ketones very rapidly) and still be in a fasted state.

http://www.dangerouslyhardcore.com/1270/intermittent-fasting-part-1/

Bruno
Bruno
4 years 5 months ago

This is very good info!

Bruno
Bruno
4 years 5 months ago

Tried it!

I’m not sure if it had much of an effect on my ketones… and it was kind of hard to choke down the feeling of straight oil, since the oil sits on top of the coffee.

I might try this again in the future, but I think I might just stick with plain black coffee on my fast days.

Matthew Caton
4 years 5 months ago
If you are training too much or too hard, as I find most people are, then you will not find fasting enjoyable, and you will not be coherent or productive during a fast. You shouldn’t have more than 2-3 hard training days every week. Hard training shouldn’t extend past an hour. Keep exercise light, such as walking, on other days. Some people have an issue getting in enough whole food in a 4 hour eating window, especially with the satiating effects of protein. You may have not been eating enough, which would have led to low levels of leptin. 16/8… Read more »
Kate
Kate
4 years 5 months ago

I agree, I workout (LHT),fasted 3 days/wk, and in between do some LISS, usually walking, I love it. I typically workout between hours 16-18and of my fast, my fasts are usually 16-20 hours with no problem. However,if I throw in a HIIT workout too often or my LISS becomes more intense than usual I can always feel it in my next fast right away.

Michal
Michal
4 years 5 months ago
I think that the series of articles was about IF, intermitent fasting. What you are doing is consistent feast /famin scenario. There are some great books on this type of ‘eating window’ lifestyle. eg. Ori Hofmekler has one, which might help “The warrior diet”. He dosent advocate a total fast in that non eating window either ! Fasting for me isnt so much about not going without food all the time, I fast 24 to 36 hours once a week ! Ocasionaly missing a meal and I dont eat past 6pm, but thats just me. Start off with one day… Read more »
Bruno
Bruno
4 years 5 months ago
I fast twice a week for 24 hours. I like to have a big workout right before my long awaited meal. I find that I work harder when I have a hot dish waiting for me, and it feels super rewarding to finally eat. I do feel like “that guy” sometimes, though, because I don’t like doing anything active on a full stomach – but a few pieces of jerky or a couple eggs wouldn’t be enough to dissuade me. I played Ultimate Frisbee just last night for the first time this season. I think this is the first time… Read more »
Matthew Caton
4 years 5 months ago

I’m with you on that. It’s not so much that I find I can’t perform when I’m fed, as much I find that the fed state is a time for relaxing.

I find the energy to train hard and be active when I’m fasting, and I know I enjoy it more.

Christina
Christina
4 years 5 months ago

And by the way, I’m very glad you’re writing about this! You’re right — there is not much out there in the way of resources about this! I’ve tried to find something helpful regarding keeping a consistent routine with my training (i.e. able to go as hard as I want when I want to (although for me that certainly doesn’t mean 100% every day anyway)) while able to incorporate fasting and there’s not much. Thanks!

Dan
4 years 5 months ago

Another valuable fasting resource, which I learned through MDA, is leangains. com

Primal Texas
4 years 5 months ago

Ditto. Leangains is a great resource of information and ideas on the topic.

He offers a variety of ways to approach it… because we lead a variety of different lifestyles.

One of Mark’s last lines really resonated with me: “Do what works for you and if you find that fasted training qualifies, so be it.”

Daniel Wallen
4 years 5 months ago

Christina, if you enjoy the Lean Gains plan, here is an easy calculator to get you started with calorie/nutrient intake guidelines. This saved me a lot of time, trouble, and stress. I don’t count calories on a daily basis, but think it’s good to begin with a basic plan. http://www.1percentedge.com/ifcalc/

Matthew Caton
4 years 5 months ago

I offer all my online clients a fasted workout protocol and meal guidelines. My entire protocol is centered around fasting and helping my clients work their way into fasting and fasted training.

Right now I am offering two weeks of my online services for less than 25 dollars.

If this doesn’t interest you, I also write extensively on the benefits of fasting and weight training on my website.

Tee
Tee
4 years 5 months ago

Have you no shame? Back off dude with the making money shit.

Cory Ellerbroek
Cory Ellerbroek
4 years 5 months ago

Personally, I appreciate all of the FREE knowledge Matt has shared with us. He obviously has a very good understanding of the subject and is nice enough to share it with the rest of us. I don’t mind the occasional plug for his business, he doesn’t do it in every post.

Steve
Steve
4 years 5 months ago

Really enjoy this series. I have been “primal” for quite some time (over a year) and have been doing 1-2 24 hour fasts a week ala Brad Pilon’s Eat Stop Eat for over a year now, and find that both blend perfectly well together and are easy for me. Some of my most intense workouts (measured against previous times/weights/reps, etc) have occured 23 hours into a fast. It’s all a matter of what works for the individual.

Kiki
Kiki
4 years 5 months ago

I have been exercising since I was 18 in a fasted state (swimming, hiking, weight lifting, stadium climbing etc). I usually exercise first thing in the morning. I am 44 now. I always perform better on an empty stomach. I do drink at least a gallon of water a day and more when I’m exercising. Since I cut out all grains (2 years now), I have noticed my performance and recovery have improved.

Harry Mossman
4 years 5 months ago

I do water “aerobics” mid-morning once a week. (I put aerobics in “” because it involves full sprints and lots of resistance.) Often I will supplement with some overhead weights in the gym. I nearly always do the workout with only water or (decaf) coffee and have plenty of energy.

zack
zack
4 years 5 months ago

“A 2009 study found that subjects who lifted weights in a fasted state enjoyed a greater “intramyocellular anabolic response” to the post-workout meal. Levels of p70s6 kinase – a muscle protein synthesis signaling mechanism that acts like an “indicator” of muscle growth – one hour after a fasted workout doubled levels compared to one hour after a fed workout (in the same group). In other words, fasting boosted (physiological indicators of) post-workout muscle growth.”

This makes total sense. You don’t eat the animal then hunt it… you hunt it then eat it!

Jeffrey of Troy
4 years 5 months ago

As much as our ancestors were HUNTER-gatherers, they were also hunter-GATHERERS. It’s not like animal food was all that was available, such that once they finished off the last animal, they had no food at all until they bagged the next one.

It is at least as plausible that they were eating the gathered plant food – i.e., carbohydrate – pre- and maybe also during-the hunt; then, high-pro, high-fat post workout.

“Fasting as much as possible” or “never fasting” are not the only two options.

Bennett
Bennett
4 years 5 months ago

Unless, of course, you have some jerky left from yesterday’s hunt. Or last week’s, even. Or you fished, or you caught something in a trap, or your family caught something earlier, or you went foraging for nuts, berries, roots, shoots, and insects, and then went hunting after breakfast, while you had a full stomach and high energy.

Helps to remember that not only were ancient humans resourceful, they were also social–or else they weren’t apt to be long-lived.

Matthew Caton
4 years 5 months ago
I agree with you on this. Hunting probably would have taken place when food wasn’t just lying around to be eaten, otherwise people would not have been hunting in the first place. Makes sense, right? However, these adaptions also make intuitive sense from and adaptive perspective. Your body will synthesize more protein and store more glycogen in response to fasted training, because it is adapting to the environment, or the state your body is when training usually takes place. Your body is trying to adapt to the metabolic demands you are placing on it by storing more glycogen and protein… Read more »
Fritzy
Fritzy
4 years 5 months ago
Thanks for the great post, Mark. As of late, I lift heavy and trail hike fasted–simply because it makes no short-term difference in my training or enjoyment of the activity and it’s more work to prepare and consume food before hand. I also wait until I’m hungry to eat after an exercise session, which is sometimes immediately and sometimes 1-2 hours post workout. I will have a peice of fruit 1/2 hour before sprints though, as I gas-out quickly if I do it fasted. I have noticed, over the course of the past few months that my strength has improved… Read more »
Dan
4 years 5 months ago

My wife noticed how much more focused and stronger I have become since working out in a fasted state. I hear ya!

Sarah Redmon
Sarah Redmon
4 years 5 months ago

I am training for a half marathon (and not enjoying it) and I have found that I have the most success with distance in the morning. I do have some coffee and maybe a smoothie an hour before going out to take the edge off and give me a little fuel, but much more than that and I feel sluggish and heavy. When I run later in the afternoon after work I feel like I am always struggling the whole time. I feel slow, heavy, and I tend to get side aches. So this all makes sense to me.

Philmont Scott
Philmont Scott
4 years 5 months ago

Sorry for pointing out the obvious, but if you are not enjoying your training for your half marathon, then maybe you should stop and do something else. I don’t mean this to be snarky or mean. I can’t imagine enjoying running that much.

Fritzy
Fritzy
4 years 5 months ago

I have to second Philmont Scotts sentiment–life is too short to put so much time and energy into an optional activity you don’t enjoy.

Lynna
Lynna
4 years 5 months ago

I can run and walk fasted, but if I do heavier exercise, such as my hour long TRX class or go to a BodyPump session, I need to have eaten earlier in the day or I run out of steam.

Matthew Caton
4 years 5 months ago

Those kind of training sessions deplete a severe amount of glycogen. Brief HIT strength training sessions lasting 30 minutes to and hour will not have this effect. Glycogen depletion will be moderate.

Ashley
Ashley
4 years 5 months ago
While reading this I realized that just yesterday morning I’d worked out in a fasted state. I was so motivated to work up a sweat and felt so energized that I hadn’t even considered eating something before. After my 30 minute session I didn’t eat for another few hours, just because I was busy with house work and I wasn’t hungry yet. I don’t always work out fasted but when I do, it’s not usually planned. I just do what I feel like and give my body what it needs. Definitely would NEVER have been able to go that long… Read more »
JoeBrewer
JoeBrewer
4 years 5 months ago
I have been mostly primal for 2 years now. I try and hold off eating each day until I get truly hungry. Sometime that is 9am, other times it’s after one of my 12 noon lifting workout and can be as late as 2:30. I have a loss of appetite after lifting for an hour or more. I have sometimes tried to hold off eating until after my noon lifting and I have found that on days when I had to really work at not eating due to hunger, the workouts suffered. On days when the fast came easily, the… Read more »
Cheryl
Cheryl
4 years 5 months ago

I walk 3 miles every morning fasted (usually about 10-11 hrs at that time) and find I am more energized afterwards. It also seems to make any “hunger pangs” disappear.

Dan
4 years 5 months ago
I have been participating in 16-20 hour fasts since the beginning of January 2012. I have also been following the Body By Science Big 5 workout since Christmas 2011. I have been Primal for more than two years. Yet my weight, lean body mass, body fat and measurements have not changed! Granted, I do have leaky gut and hashimoto’s; these have been leveled out through diet and lifestyle. I absolutely love IF and Primal as a lifestyle and will continue it indefinitely. Thanks Mark, for showing us the way! I just cannot figure out which piece of the puzzle I… Read more »
mommymd
mommymd
4 years 5 months ago

How about trying to get into and stay in ketosis? If your 100 grams of carbs come all at once, you will be leaving ketosis. Give yourself 3 weeks of carbs as low as possible (leafy greens only), no tubers, no nuts, no seeds. See what happens.

Mike P
Mike P
4 years 5 months ago
I exercise in a fasted state 5 days a week. I exercise first thing in the morning before I go to work, so I don’t really have time to eat something, let it digest some, and then exercise. I go into work early in the morning so I can leave earlier in the afternoon… so I have time to play at night 🙂 If I am going to exercise with a meal in me, I need to have at least 30-60 minutes post-meal before I feel like I can exert myself without feeling gross. I have been exercising in a… Read more »
Lisa
Lisa
4 years 5 months ago

I have been eating primal for over two years and last year did most of my long distance cycle training in a fasted state. Three and four hour rides at low intensity felt wonderful! I participated in 5 “events” and usually ate a banana or homemade trail mix during the ride. Bananas are perfect high octane! I had my Best season ever.

Pete
Pete
4 years 5 months ago
I have exercised twice now at the end of a 24 hour fast. First was a week or so ago, I was just curious how I would do cycling on hour 23. Did a 12 mile ride, had a great experience and felt no loss of energy or Bonk. Still had the tingle of hunger, but nothing that wasn’t easily manageable. This week I went for a 3 mile trail run after fasting. It was a little more difficult, but still overall a good experience. So much for the need to carbo load prior to working out. I also went… Read more »
cancerclasses
4 years 5 months ago
Here’s the absolute best reason to exercise and work out in a fasted state, and specifically a carbohydrate and glucose restricted or fasted state: CARDIAC FUNCTION.  “Methodist DeBakey Heart & Vascular Center scientists learned that starved heart cells maintain normal calcium cycling and basic mitochondrial function far longer than non-starved cells during periods of extreme stress. The findings… add to a growing body of scientific evidence that suggests the consumption of less energy — while maintaining balanced nutrition — can benefit tissues by enhancing cell performance and reducing DNA damage associated with the aging process. “We are connecting several loose facts… Read more »
Wafaa
Wafaa
4 years 5 months ago
Thanks for the great post! It might be interesting to note as well that during Ramadan, people tend to gorge themselves on “sweets”. I mean seriously ridiculous amounts of sweets with all that sugar syrup. They seem to think they won’t last the day without loading up on carbs! I think the wisdom of spending a month eating less gets lost, and a lot of people end up stuffing themselves and eating more in those few hours of dark than in a normal day. Last year’s Ramadan was so much easier when I had given up all sugar, and tried… Read more »
Imran
Imran
4 years 4 months ago
Hi Mark, Thanks for this post. I am a Muslim who went Paleo in July last year, 2 weeks before the start of Ramadan. I had read about it, and then experimented on myself. Where I live in London, the fast was from about 4am to 8/830pm in the evening. I went completely cold turkey on refined carbs: no grains, no wheat, no potatoes, or corn, and very little fruit. If I had fruit, it was only a little and late at night so I wouldn’t experience the hunger cravings that came followed the sugar rush. I didn’t have any… Read more »
Vanessa
4 years 5 months ago

I have been doing a 16/8 daily IF for 1 1 /2 years and training in a fasted state. I have played with all different pre/post workout fuel options and prefer to train fasted and then eat a large meal afterwards.

Gillian
Gillian
4 years 5 months ago

I’m confused.
One should eat protein and carbs 30-60m post workout to build the muscles
Am I wrong?

Matthew Caton
4 years 5 months ago

What is best for building muscles is not always best for your health. I try to balance these two goals.

Phil
Phil
4 years 5 months ago

As I have heard it, no. That’s commonly heard, but leaving eating 30 mins plus means you get the most out of a post-exercise growth hormone surge (GH and Insulin compete for receptors, so carbs are a no for GH)..and increased post-exercise insulin sensitivity (which will drive more protein/nutrients into muscles for muscle synthesis) lasts a few hours after the exercise. So, it’s best left a bit.

thomjen
thomjen
4 years 5 months ago
Due to these articles, I have been trying just fasting 8-9 hours a day. Picking a time when it is inconvenient to eat, or easy to skip eating. I felt really great. I drank mint tea – peppermint helps with hunger – and I noticed a big difference. I still had three meals, I am just giving my body a break from digesting. I ended one of them in a cross fit workout, which as someone else mentioned, started slow, but felt better as I progressed. My mind is much clearer and I felt some weight loss. I am really… Read more »
Ghee
Ghee
4 years 5 months ago
I am a HUGE proponent of fasted training. After a glutenous honeymoon in September, I decided to give fasted training a try. Now I typically begin a fast after dinner, continue it through the morning, workout around noon, and then break the fast with a nice refeed for lunch. I do follow Martin Berkhan’s advice and have 10g of BCAA before a workout, but other than coffee (black) and water, that’s it. I got over the mental hurdle (CW telling me that I needed to eat for energy) pretty quickly and I can honestly say that I haven’t noticed even… Read more »
Jake
Jake
4 years 5 months ago

im impressed that you can follow 5×5 fasted

Ghee
Ghee
4 years 5 months ago

Thanks! I’d love to say that I’m a beast for being able to do that, but really I saw no change in energy when I went to fasted workouts (I technically started 5×5 a few months before starting to train in a fasted state).

BTW, although my honeymoon was no doubt filled with gluten, I really meant “gluttonous.” hehe.

Seth
Seth
4 years 4 months ago

I find everyone’s comments interesting. Although there may not be a lot of tests regarding fasting and training I highly recommend everyone to check out Brad Pilon’s Eat Stop Eat. In my opinion it is the best technical and informational guide there is and definitely has good information regarding training.

Katrina
Katrina
4 years 4 months ago

To me, that’s the best part of fasting–simply not worrying so darn much about food and eating! I used to plan out my six “balanced” meals a day (protien, fat, carbs, fiber, etc.) I had lists and lists with the counts for everything! I carried food with me everywhere! I still carry nuts with me, but now I just eat when I’m hungry and eat simple things like nuts, meat, occassionally some veggies and fruit, and cheese. Easy Peasy Lemon Squeezy!

Nate
4 years 5 months ago

Wow…fasting every other day sounds a bit intimidating, but maybe introducing some fasting periods a few times a month would be a good place to start. I’m definitely curious since I’ve heard all of the studies about calorie restriction and increased lifespan.

kamaile73
kamaile73
4 years 5 months ago
I have been committed to the primal diet since January of this year and recently (last month or so) began experimenting with IF. Mon, Tues, Thurs & Fri I’m on a 16/8 schedule and I fast all day Wednesday which usually amounts to about a 30-36 hour fast. On the weekends, I eat when I’m hungry… I dance hula on Wednesday nights for about 2 hours duration (about 20 hours into the fast) and have found that my endurance, mental clarity and ability to focus on the dance have all increased since I started fasting. It’s not a consistent, intensive… Read more »
yoolieboolie
yoolieboolie
4 years 5 months ago
I am a Bikram yoga fan, and over the past 18mos I’ve found that the 90 minute classes are easier for me to enjoy in the morning, when I haven’t eaten for 12-16 hours. I do sometimes eat 1/2 a banana an hour or two before class so I don’t bonk before class is over, and after class I’ll often drink a coconut water to help with recovery. Usually I end up going 20 hours without a meal because I’m not hungry after class. Since going Primal last month I’ve reduced my classes from 4-5x/wk to 2-3x/wk so I can… Read more »
WaltZ
WaltZ
4 years 4 months ago

@yoolieboolie: Thanks for sharing the insight with Bikram yoga in the mix! I’m also curious if others have successful strategies for incorporating fasting with primal and Bikram Yoga. I’m going to try it this weekend, fasting from dinner Friday until after a noon Saturday class.

Odille Esmonde-Morgan
4 years 5 months ago

Interesting stuff, thanks Mark.

I always fl much better doing my early walk or swim on an empty stomach, or just a cup of beef extract at least an hour before. Anything more in the tum makes me fel nauseous. I’m so glad to see it is helping my muscles too!

Stacy jett
Stacy jett
4 years 5 months ago

Remember, there is nothing natural but only damaging if one chooses to use “chemotherapy” as a cancer “therapy”- building of the immune system is number one priority- something chemotherapy does the exact opposite of. Natural foods and methods are much more productive. :~}

DavidDP
DavidDP
4 years 5 months ago

I’am on a paleo diet for just over 6 months now, but I can’t do a fast of any kind and always hungry. I see all this talk about listen to your body and how you should feel sated eating primal, but I eat 4-5 times a day total around 3.500kcal (60% fat, 30prot, 10carbs). Does anyone have similar issues?
(sorry about poor english, I’m from Brasil)

WildGrok
WildGrok
4 years 5 months ago

Hi:
I have a friend at work with the same issue. Check again your carbohidrate grams per day, maybe they are more than you think. Some people have more difficulties than others. It will not hurt if you check your thyroid with your doctor. Regards and good luck!

Shuahh
Shuahh
4 years 5 months ago

I’m a hardcore skier, and on powder days I’ll head out the door with nothing but coffee in my belly then charge hard for hours before I lose energy. Then I usually eat post-ski. But I can ski many thousands of vertical feet in a fasted state just fine.

Matthew Caton
4 years 5 months ago

I have written extensively on the benefits on fasting and strength straining on my website. I explain how growth hormone, autophagy, and telomerase all benefit from fasted training and how these things can actually reverse aging.

I always try to train completely fasted. No BCAA or whey protein, beforehand. I just deadlifted 315 lbs for five reps three days ago completely fasted.

Pekka
Pekka
4 years 5 months ago

Matthew,
What`s you opinion if I break my fast after 14 hour with 15g wheyhydro at 10am and again 15g wheyhydro at 1pm, weight training at 3pm.
Do you think it`s better to go totally fasted till training ( 19hour fasting )?
Hope you answer or somebody else.

PrimalNewborn_M
PrimalNewborn_M
4 years 5 months ago
I’m relatively new to the primal life — went low carb about 2 months ago and finally primal about a month ago — and recently discovered intermittent fasting too. Before ditching grains, sugar and starch, I never would have thought any kind of fasting was for me, but now that I am fat-adapted I have found that I thrive on a noon to 6pm eating schedule, ESPECIALLY when I have done some kind of moderate cardio exercise (a long walk or a 40-minute workout on the elliptical) with nothing but a coffee beforehand. For me, working out in this condition… Read more »
WildGrok
WildGrok
4 years 5 months ago

I fast once a week (almost 24 hours), usually on Tuesdays. The fast day does not interfere with my workouts. In the beginning of my fasts like one year ago at the end of the day I felt hungry like hell and as soon as I got home I had to eat something. Not anymore: after the (usually) 22 hours I am ok, I could go on easily for 20 hours more.

John
John
4 years 5 months ago
I’ve been eating Paleo for about 6 weeks and have lost an amazing 23lbs. Started at 213lbs. and now weigh 190. I just started adding IF using the 16/8 ratio 3 or 4 days a week. I recently checked out leangains.com and it seems he is quite fat conscious which surprises me and seems to embrace carbohydrates as well. Not sure what to think as his clients get amazing results. I’ll probably stay Paleo focused while including IF as I’m feeling great and see no need to change. Anyone else wondering about this feel free to comment, I’d be interested… Read more »
Daniel Wallen
4 years 5 months ago
John, Martin is catering to a crowd of people who want to get buff. Mark seems more focused on general health and fat loss. I think if someone has a lot of weight and isn’t too concerned about building muscle, primal is the way to go. If someone is skinny and trying to gain muscle, Lean Gains would be a better fit. I used to be 220 lbs and mostly followed a primal diet. I cut down to 170 and decided to switch focus to building muscle, so now I’m following Martin’s suggestions on spiking carb intake. Both approaches work,… Read more »
Chris
Chris
4 years 5 months ago
I recently (2 months) started following the Martin Berkham Leangains method to IF, and lift at the end of the fast and eat immediately afterwards. I actually prefer this as I like working out on an empty stomach. I look back to all my training over the years when i thought you HAD to eat beforehand, and there were some times I’d go to the gym on an empty stomach because my schedule didn’t allow a meal beforehand. I went in expecting to have a crappy lifting session, and would be surprised to have a really good one. Thought it… Read more »
Daniel Wallen
4 years 5 months ago

I used to be the same way. I’m happy you actually had productive training sessions–if it happened to me, I was so obsessed with frequent intake that I created a self-fulfilling prophecy: I expected a shitty workout, so I had a shitty workout. Now that I understand why fasting works, I don’t have the same problem–they’re actually more productive than before. It makes more sense, too, from Grok’s standpoint.

Tracy Seman
4 years 5 months ago

I have always trained fasted by training at 5 a.m. But I would rush home and have that post workout balanced meal.

The past 8 weeks I actually started leangains protocol and finish dinner by 7:30 p.m. CrossFit at 5:30 a.m. and eat first meal @ 11:30 a.m. I am so happy with the change. My workouts are not suffering and I have leaned out. I actually feel like I have more energy.

Ben
Ben
4 years 5 months ago

Coming from the Leangains approach are you doing the 10g of BCAA a couple of times between your crossfit session and your fast breaking? It sounds pretty similar to my situation but I’d prefer not to supplement but worry that I’m doing more harm then good by working out mid fast.

nate pennington
4 years 5 months ago

Thanks for the insight Mark..glad I came across your blog. Running is what I have done for the past 20 years. I certainly feel your post makes a great deal of sense. I have done some of my best long runs without even eating breakfast…did a 20 miler in 1.50.02 (5.30 aver. per mile) on water alone…more running coaches are gearing more to depletion type efforts to teach the body to run with less in the tank.

Brad
Brad
4 years 5 months ago

The thing I don’t get is the absolute fastest any protein food can be digested is about 1.5 hours, with many types of proteins being significantly longer. I would imagine most fats except coconut oil would be similar. So setting aside BCAA that might be absorbed fast, if you drink a pre-workout (low carb) protein shake, would that break a fasted workout? It seems the nutrients wouldn’t really hit until after the workout. And if you want to make sure the nutrients hit right after, you should drink it about an hour before exercising? thoughts?

Brad
Brad
4 years 5 months ago

In my case I’m talking about a 20 minute HIT weight lifting session.

Brad
Brad
4 years 5 months ago

Btw, does anyone else get muscle cramps at times? I’ve noticed since I started eating Paleo lowish-carb and started doing high intensity exercise like sprint intervals and HIT lifting that I get calf cramps sprinting, toe and calf cramps from the leg press, and minor forearm cramps from doing pulldowns and deadlifts.

Shadowfax08
Shadowfax08
4 years 5 months ago

I am also curious about the increase in tendency for cramps. Is it due to the primal diet or perhaps have I become deficient in some mineral/nutrient due to cutting so many carbs( limited veggies/fruits as well for Ketosis).

Bruno
Bruno
4 years 5 months ago
I’m kind of the opposite. I used to get cramps every time I would play a soccer or ultimate frisbee game. Every time! And I used to stretch beforehand every time. I stopped stretching. I’ll just do one of the low super-squat stretches for a good 30 seconds or so before I do anything active. My legs seem good to go. I haven’t had a single cramp since going Primal and dropping ‘standard’ stretching. Some suggestions are to be sure you are hydrated. Squeeze a lemon or lime out into some water and put 1/8 or 1/4 tsp on salt… Read more »
Scott
Scott
4 years 5 months ago
Those of you experiencing dizziness, light-headedness and headaches during fasting period might consider increasing your salt/mineral intake by drinking a few cups of boullion during the day. Your body will use water more efficiently during carbohydrate restriction and will tend to shed it along with the minerals which will cause the above symptoms. Alternatively you could make your own bone broth on the weekend (a gallon or so) to be consumed throughout the week. In this case, you can of course make use of sea salt. This subject is treated extensively elsewhere on this website as well as in “The… Read more »
Vlad
Vlad
4 years 5 months ago

Should fasting be considered when you try to GAIN weight? Right now I am actually eating 3 meals a day and exercise 2-3 time (LHT), sprints once a week and of course of lot of walking – in order to gain some weight.
What do you think of that?

Tom Parker
4 years 5 months ago

Hey Mark – I’ve not fasted for a while but I have worked out fasted in the past and it’s worked fine for me. I didn’t really see any massive improvements in my performance compared with working out after a meal but I didn’t suffer either.

Chris
4 years 5 months ago

As mentioned at the tail end of you article – I have definitely benefitted from strength training on an empty stomach in the past. Both my squat and deadlifting PR’s have been on a fasted saturday session.

I get the feeling this is due to the body not having to ‘split focus’ on digesting and strenuous physical activity but have no hard evidence – thoughts?

Christian
Christian
4 years 5 months ago
Mark, here’s my story. I’m in IT but at night/weekends I’m a recreational rock climber. I climb at a 5.10+ / 5.11- level and I’m 290 pounds. Let that soak in for a sec 🙂 Prior to going on the Paleo Diet + IF in January 2012 I weighed 340 pounds and I was climbing at a 5.10 level (not 5.10+). I always ate before I went climbing and I felt sluggish. Now I often go to the gym in a fasted state and I find that climbing in a fasted state vs. full/happy tummy is interesting, I can push… Read more »
Ben
Ben
4 years 5 months ago

I love fasted training. My only concern is the timing of everything – I typical use an eating window from 12:00-8:00 pm, however my only chance to consitently lift heavy is first thing in the morning (6:00 am). I don’t mind working hard fasted and I feel great doing it but I feel almost ‘obligated’ to eat afterwards which would require shifting my window which wouldn’t really work for me.

Anyone have experience training mid fast instead of ending one with a workout? I’d be interested to hear others experiences.

Sian
4 years 5 months ago

Thanks to these articles I’ve started fasting one evening a week (am taking it slow!).

Am amazed at how easy it is (been primal for a year) and how I actually now really look forward to doing it. I love the feeling of calm contentment it gives me and the wonderfully refreshing sleep it produces. I feel like it gives me a weekly ‘reboot’. The more I adhere to the primal principles the easier it is. Who knew fasting could be so enjoyable?!

trackback

[…] Train Fasted – Don’t drink a smoothie or eat a Cliff Bar before you exercise. This is a topic too large to cover in this post. The short reason is your body is primed for fat loss and muscle gain when you train fasted. This is how nature works. Recommended reading: Why Fast? Part 5 Exercise. […]

Alex Good
Alex Good
4 years 5 months ago

I’ve technically been fasting for about half my life (running late for school and not eating until I got home most days) and I can definitely confirm that my performance suffered back then.
It does not now so food choices do affect the efficacy of fasting.
Also, I find that my training is definitely better fasted.

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