Fasted Workouts: When They’re More Effective (and How I Incorporate Them)

Fasted workouts are a controversial topic in the fitness world. To some, the idea of working out without “carbing up” or doing the pre-workout protein shake is unthinkable. Won’t my performance suffer? Won’t my muscles shrink? Won’t my body think I’m in the middle of some horrible famine and go into starvation mode?

To others, fasted workouts are sacred tools, the perfect antidote to modern decrepitude. When I train in a fasted state, I can will my adipocytes to release fatty acids and feel the heat as they burn, hear the barely audible *pop* of muscle satellite cells replicating and proliferating, and see visions of my future physique through my gaping third eye. 

Where does the truth lie? Let’s look….

To begin with, the evolutionary argument—the Grok logic—for fasted workouts is extremely appealing and intuitive.

Humans did not evolve with access to 24-7 fast food restaurants, grocery stores containing hundreds of millions of calories, and food supplies so ample that we often throw out half of it before we’re able to eat it. If paleolithic humans wanted to eat, they had to hunt or gather something—both of which require the expenditure of caloric energy—often on an empty stomach. In fact, these “workouts” for hunter-gatherers probably occurred more often than not in a fasted state.

This doesn’t mean that fasted workouts are ideal or optimal for health, performance, and fat loss. It does suggest that humans have the capacity for working out in a fasted state without falling apart or losing all the benefits normally associated with exercise. The question is if fasted workouts offer any special advantages.

Today, I’m going to dig into the literature to explore the most frequent questions and claims about fasted workouts and arrive as close to the truth as we can.

Are Fasted Workouts Good or Bad for Muscle Gain?

Let’s take a look.

One common argument is that since you’re not eating, which already “stresses” the muscles and deprives them of structural substrate, stressing the muscle with exercise causes it to “melt away.” This is overly simplistic, if attractive.

For one, that first bit is wrong. Reasonable durations of fasting don’t cause muscle loss. In fact, you can do a few days of fasting without incurring any significant muscle loss. The ketones generated during the fast have protein-sparing effects, and the fasting-induced spike in growth hormone also spares muscle from breakdown. There was even a study where blocking growth hormone with a GH blocker caused fasting people to lose 50% more muscle than fasters who didn’t get the blocker.

For two, strength training itself is a powerful signal to your body that your muscles are essential tissues vital to your survival. Your body generally tries to avoid burning through essential tissues. Lifting also increases growth hormone. Paired with the fasting-induced GH boost, your muscles will be in good standing.

Okay, so fasted workouts don’t appear to be bad for gains. Are they good?

Fasted training augments the anabolic response—the ability of muscles to take up protein and get bigger and stronger. A 2009 study found that, compared to athletes who lifted weights after breakfast, athletes who lifted weights in the morning before eating had an augmented anabolic response to a post-workout protein-and-carb shake.

Are Fasted Workouts Good for Fat Loss?

This one makes sense, doesn’t it? When you don’t have exogenous calories coming in, and you go for a run or walk or bike ride, your body should burn more body fat since it’s the only energy source available. But does it actually happen?

Well, short term studies find that fasted cardio increases fat oxidation in the body. People who go for a run in a fasted state have a lower respiratory quotient, an indication of greater fat burning versus glucose burning. One study found that a morning fasted cardio session increased 24-hour fat oxidation by 50% in young men.

An increase in 24-hour fat oxidation doesn’t say much about long term fat loss, however.

Another study followed a group of healthy women for four weeks, placing them on a morning fasted cardio routine. Three mornings a week, the subjects would perform 50 minutes of treadmill cardio at 70% of their max heart rate in a fasted state. Both the fasted group and the control group (who performed the same cardio, just not fasted) maintained a daily 500 calorie deficit. What happened?

There were no differences in fat loss between groups. Both groups lost weight and lost body fat, but fasted morning cardio did not accelerate the loss. A recent analysis of the available research came to the same conclusion: no difference in fat loss or weight loss between fasted workouts and fed workouts.

I’d like to see a similar four-week study done with men, who in my experience and from reading the fasting literature tend to have a more favorable response to extremes in caloric restriction.

This isn’t a perfect fasted workout study, but it’s better than nothing. A group of triathletes was placed on a “sleep-low” program: instead of eating a ton of carbs after their afternoon workouts, they ate none at all. They depleted their glycogen with the workout, ate a very low-carb dinner, and went to sleep. Then they woke up and did low-intensity cardio in a fasted state, which is the equivalent of a normal person going for a walk. The study was interested in performance, not fat loss, but the group who did their cardio in a glycogen-depleted, fasted state lost more fat than the control group.

An old bodybuilding classic for shedding fat is the fasted morning walk. Wake up, consume no calories, and go for a brisk 20-30 minute walk. In those who are already pretty lean but want to get very lean (like bodybuilders preparing for competition), fasted low-level cardio can be very effective. This is the hardest body comp transition—from lean to very lean. Lean is what the body “wants,” and going lower requires getting over the natural tendency to hold on to diminished body fat stores. A fasted walk, jog, or cycling session performed in the aerobic zone almost forces the body fat to release into circulation. Insulin is low. Sensitivity is high. The stage is perfect, in theory.

Are Fasted Workouts Good for Performance?

Yes and no.

To answer this question, we must note the distinction between training and competing. You might perform worse in a given workout if you’re fasting. You’ll probably perform better if you’ve eaten. But if you’ve consistently trained in a fasted state, the metabolic and muscle adaptations you’ll acquire will boost performance when you compete in a fed state. And that’s everything, isn’t it? While it’s fun to go hard in a workout, test your PR, and treat your training session like the world championship, the real reason we train is to adapt to the training and get better, fitter, and faster—whether for a legit competition or to simply get healthier. A fasted workout trains you to perform under difficult physiological conditions of low fuel availability, and that comes in handy. You probably wouldn’t enter a race or powerlifting match in a fasted state, but the fasted workouts you did in the months leading up to competition make you more likely to win.

The two are complementary. Train fasted, race fed.

Sprinting performance appears to suffer. In one study, sprinting athletes who had fasted had impaired speed and power thanks to less springiness. In another, fasted sprinting led to slower reaction times. Again—the question is, do the training adaptations you get from sprinting in a fasted state make up for the acute losses in performance?

Ramadan fasters (no food or drink during daylight hours) who engage in sprint training improve their soccer-specific endurance performance. They may suffer during the training, but they get good training effects.

As for strength training, there isn’t much solid scientific evidence that the fasted state improves or harms performance. One thing I’ve noticed—and have also heard from dozens of anecdotal reports—is that fasted workouts fill me with a special sort of energy. For lack of a better term, it feels more “Primal,” like you’re actually on the razor’s edge of desperation and performance, where your entire being is focused on lifting the weight, sprinting the hill, or spearing the deer that represents the difference between food for a week and total starvation. It’s pretty cool.

Some people report the opposite. Some people seriously lag if they haven’t eaten. They need something in their bellies to have a good workout. This is a subjective thing, and you’ll probably find that it changes from workout to workout. For example, strength workouts and low level aerobic activity (hiking, walking, paddling) go well for me on an empty stomach, while I prefer to have something light to eat before really intense Ultimate Frisbee matches. Figure out what works for yourself.

Implications for Certain Populations and Conditions…

Type 2 Diabetes

Fasted training improves several physiological markers that are especially relevant to people with type 2 diabetes. For one, it improves insulin sensitivity. The basic definition of type 2 diabetes is “extreme insulin resistance”; fasted workouts counter that insulin resistance. It also improves fat burning, another deficiency common in type 2 diabetes.

Keto Dieters

Keto dieters and fat-adapted folks on low-carb, high-fat programs seem to do better in the fasted state. If you’re already adept at burning your own body fat and training in a low-carbohydrate state, training in the lowest-carbohydrate state—a fasted one—isn’t a big leap.


As I’ve written before, women tend to react more poorly to intermittent fasting, especially fasts exceeding 14 hours. They are simply more sensitive to caloric restriction, seeing as how their biological “programming” prefers they have a steady source of calories in place for growing, feeding, and nursing babies. Whether you have kids or not, that’s what a significant portion of your DNA is geared toward.

That’s not to say fasted training doesn’t work for women. It just might not do anything special compared to fed training. For instance, this study found that whether overweight women did high intensity interval training in a fasted or fed state had no effect on the benefits. Both types of training worked equally well, improving body composition and the ability of the muscles to burn fat.

Other research finds that women can benefit from fasted training, though men may derive unique benefits. In another study, men and women performed fed and fasted endurance training. Both men and women saw better VO2max increases when fasted, but fasted men saw bigger boosts to muscle oxidative capacity. Fasting helped both in this case. It just helped men a little more.

How I Use Fasted Training

These days, most of my workouts are performed in the fasted state. Anything resembling lower level “cardio,” like walking, hiking, standup paddling, and bike rides are all done totally fasted.

Before heavy lifting or HIIT sessions, however, I’ll drink 20 grams of collagen peptides with some ketone salts and often creatine monohydrate. This isn’t to “fuel” me. The collagen provides the raw material my connective tissue (tendons, ligaments, cartilage) needs to adapt to the training stress, the creatine provides the substrate for quick ATP generation for short bursts, and—this is speculative, mostly—the ketones provide brain fuel to prevent “bonking” and act as an epigenetic signal for muscle preservation. This drink doesn’t contain many calories, nor does it provoke a huge insulin response. I’m technically breaking the fast, but I’m retaining most of the benefits.

I always continue the fast after my workouts. Going a few more hours without eating enhances the HGH response, which helps spare muscle burning and augments the adaptive responses. The ability to comfortably fast after a training session is a good sign that you’re fat-adapted. If I were trying to maintain some elite athletic schedule, I’d refill my glycogen stores, but I’m not chasing performance anymore. It just doesn’t make sense to burn through them and eat a bunch of carbs only to go do it again.

I don’t train in a fasted state for magical effects. I’m not expecting any miracles and neither should you. But I do think every healthy human should be able to complete a fasted workout without falling apart or losing more than a step.

I can. How about you? Ever try fasted workouts? How do you use fasting to augment your training?

Thanks for reading, everyone.


Deldicque L, De bock K, Maris M, et al. Increased p70s6k phosphorylation during intake of a protein-carbohydrate drink following resistance exercise in the fasted state. Eur J Appl Physiol. 2010;108(4):791-800.

Marquet LA, Brisswalter J, Louis J, et al. Enhanced Endurance Performance by Periodization of Carbohydrate Intake: “Sleep Low” Strategy. Med Sci Sports Exerc. 2016;48(4):663-72.

Iwayama K, Kurihara R, Nabekura Y, et al. Exercise Increases 24-h Fat Oxidation Only When It Is Performed Before Breakfast. EBioMedicine. 2015;2(12):2003-9.

Schoenfeld BJ, Aragon AA, Wilborn CD, Krieger JW, Sonmez GT. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr. 2014;11(1):54.

Aird TP, Davies RW, Carson BP. Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis. Scand J Med Sci Sports. 2018;28(5):1476-1493.

Cherif A, Meeusen R, Farooq A, et al. Three Days of Intermittent Fasting: Repeated-Sprint Performance Decreased by Vertical-Stiffness Impairment. Int J Sports Physiol Perform. 2017;12(3):287-294.

Cherif A, Meeusen R, Farooq A, et al. Repeated Sprints in Fasted State Impair Reaction Time Performance. J Am Coll Nutr. 2017;36(3):210-217.

Aloui A, Driss T, Baklouti H, et al. Repeated-sprint training in the fasted state during Ramadan: morning or evening training?. J Sports Med Phys Fitness. 2018;58(7-8):990-997.

TAGS:  fasting

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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47 thoughts on “Fasted Workouts: When They’re More Effective (and How I Incorporate Them)”

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  1. I fast through the workout (nothing preworkout) and then fast 45min post workout at which point I drink a whey protein shake. Then I wait another hour or so to eat a fatty meal, a little after that when I get hungry I open up my macro’s.

  2. Thank you, Mark. Been wondering about the effIcacy of fasted workouts. I stopped eating breakfast when I went primal over 5 years ago. My workouts are always in the morning, sometime before lunch: Rock climbing, bouldering, HIIT, sprinting, four days a week. Plenty of rest days, though my job, bar tending at the site of the East Coast Primalcon, Mohonk Mountain House, involves lots of lifting, pushing, pulling and quick walking for 5 – 8 hours a shift. I gained 7 pounds in two years between physicals. My triglycerides are south of 40. Nothing in my blood work suggesting adrenal fatigue. Haven’t done anything differently in those two years, except adding collagen pre-workout. I’m 57. I am not a great sleeper, though a saw palmetto/bovine prostate combo have me sleeping much better over the last month. Could it simply be age-related metabolism slow-down?

    1. Wouldn’t hurt to check your thyroid levels and your TSH levels.

      My thyroid started taking a dive near my 50 age mark. Runs in my family. Taking 50mcg a day of synthetic thyroxine made a difference I could notice even though I was not showing traditional hypothyroid symptoms.

      But yes, you can’t keep cruising though life counting on what worked in your 30’s. The 50’s are a tough transition. It’s really noticeable. So I have to keep adapting to new realities to maintain my fitness.

  3. Great article – thanks Mark. I do all morning workouts like this. I also occasionally race a local 5k fasted as I don’t rise earlier enough to eat – I might reconsider that one if shooting for a PR.

    This article answers many ponderments I have. However one question –

    Morning coffee?

    Do you take your coffee+cream prior to
    a fasted workout (on the back of you mentioned ‘breaking’ the fast with the collagen mix).

    Thanks for all you share. Phil

  4. Thank you for your article.

    As a woman, 36, 4kids, not on Keto, just maintenance carbs, I find those studies related to women’s performance in fasted state interesting. I am definitely no athlete but prefer to jog or do some lifting in fasted rather in fed state. With more than a coffee and some water in my stomach I get a lot slower/can lift less. When fasted I can maintain my performance I am more or less happy with and still do my chores without eating until 1 or 2 pm.

    So I guess I just keep doing what I do as I don’t plan to compete anytime soon and kind of like the status quo ?

  5. I’ve been fat adapted for about 6 or seven years. I ditched the energy bar before dawn patrol session about three years ago, and saw no loss of, and perhaps even a gain in endurance. It was clear that eating something before surfing was more out of habit than need.

    Then this month, right as a series of chest to head+ swells rolled for the entire month of October, I tried a 16/8 intermittent fasting routine. For me, since I get up between 3:30am and 4am to go surf in the dark, my eating window is 10am to 6pm. In bed around 8pm.

    I was already surfing fasted and naturally eating when ready after surfing so I was already kind of doing intermittent fasting already.

    The result?

    1. Faster recovery time and less DOMS (delayed onset muscle soreness)
    2. Deeper more restorative sleep
    3. More endurance (4 hour sessions in head high surf without bonking)
    4. Better focus
    5. Got even leaner.

    From my own experience I’d say the data is correct. IM and fasted exercising increases HGH which preserves and rebuilds muscle, helps sleep be more restorative, and increases metabolism. I suspect I also got a boost in my immune system.

    1. Hi Clay,

      I’ve enjoyed reading your comments on this post (and many others). Based on your mention of good surf in October, I’m guessing that perhaps you’re based in California?

      One of my primary motivations for following a Primal/keto/IF lifestyle is to optimize surfing performance. Seems we have commonalities here. Would be great to chat further.

  6. I can pretty much ONLY train in a fasted state. I usually work out around noon and won’t eat anything until afterwards. Sometimes I workout towards the end of the day instead 4-5ish and I have to make sure if I eat anything that I do it at least 4 hours in advance, maybe even more. Otherwise exercising will make me nauseous and my performance is much lower.

  7. Thanks Mark for the great article. I often workout in a fasted state and really don’t feel any negative impact at all. I often feel that my energy is high and a get a real rush out of the workout. I am also Keto, so I could be better adapted at burning fats for fuel.

    I am interested in the drink you referred to. Can you give us a detailed recipe for that?


  8. Hi
    I’m 59 year old female and 2 years ago I prepared to do a half marathon. I’d never run before though I did exercise classes to keep fit. I was interested in just finishing without stopping and not personal bests. Though the second run I completed in 2.5hrs not fast I agree but I did not stop at all on the way round. I have now done 3 half marathons in a fasted state. I also did not eat for several hours afterwards. Also I had no ill effects following the run and actually fully recovered in a couple of days.

  9. I’ve written in to Mark about this topic before, originally hoping to get an answer to a “Dear Mark” but I have noticed the “lag effect” ONLY when I eat before working out. Even if it’s two to three hours before a workout or anything as small as half a banana. If there’s anything in my stomach during a workout I feel significantly more lethargic, as if the process of digestion is consuming all my energy. This still seems somewhat out of line with what Mark posted today but interesting topic nonetheless.
    Does anyone else experience anything like this?

    1. Like you I can’t eat if I feel anything in my stomach. I have to leave 3-4 hours after eating if I don’t work out in the morning before I eat. I don’t feel the timing of my meals impacts my performance at all. Although When I have tried keto Ive found my legs feel really heavy after extended low carb periods. I’ve recently been upping carbs slightly on workout days and that has helped my performance.

      1. I meant I can’t exercise if I feel anything in my stomach!

    2. Natalie, you are not alone. Yup, I can’t workout at all with any food in my stomach. Well I can, but boy does my performance suffer. Very lethargic, weak and a heavy feeling. I feel like Superman working out in a fasted state. HIIT is also done fasted. No bonking at all in the last 7 years. I actually like to start an occasional 36 hour fast by doing an intense bodyweight workout session.

  10. What about for someone who isn’t fat adapted? I take a fairly liberal primal approach which is high in all 3 macros, am I likely to still see the benefits?

    1. I would say it will be harder. The reason being that when you are fat adapted your fat for energy utilization is very high and far more extensive then previously thought possible. Initially it was thought the human maximum was burning one half gram of fat per minute during exercise. It was also through that anything above 50%-60% of maximum effort would be 100% glucose based. But when they finally did a proper test with fat adapted athletes they were still burning fat at up to 80% of maximum output and their fat burning was 1.5 grams per minute ( three times higher than what was thought humanly possible).

      If you get fat adapted first it may be seamless to switch to fasted workouts and you may even prefer it.

      But like anything, your mileage may vary. Give it try and see what happens. Maybe you’re more ready than you think right now.

  11. This was a perfect article to read right after I finished a fasted trail run! Thanks Mark.

  12. I enjoyed this article Mark! I’m 54 and my normal weekday routine is to wake at 5:30 and then hit the 6:00 AM CrossFit class. I do the workout fasted and afterwards focus on drinking at least 64 oz of water before noon. I normally don’t get hungry enough to eat until after 11:30 or so. I’m curious about one thing, since I’m lifting several days a week, I like to take creatine monohydrate. Do I get any benefits taking it at dinner, 12 hours after my workout? Thanks!

  13. Does drinking your morning coffee affect the fasting process before working out?

  14. Mark,
    So what and where, exactly, is your gaping third eye located? Haha!

  15. I always do fasted workouts. They’re great. Fed state workouts feel sluggish and unnatural.

    Question: For aerobic exercise, I usually do short sprints but sometimes I opt for low intensity steady state MAF for 45-60 minutes. One of the benefits of a 45-60 minute session is my brain gets into the “flow” state and, I think, BDNF is generated. My question is, what’s the minimum amount of time of low intensity steady state exercise required in order to generate BDNF? I assume my 45-60 minute sessions are long enough but my short sprint sessions aren’t.

  16. 5 or 6 years ago I tried to get on board with fasting (both IF and one 24 hour period/week), I wanted all those magical outcomes for cognition and physical performance so I kept pushing it until I could no longer deny that it was just not making me feel good! I am happy that in recent years the online community has incorporates the voices of women and th e unique impacts fasting has on their hormone state. I now give myself a solid 12 hour break and eat when hungry (i pract 6 am Ashtanga, typically only with some fatty coffee) and feel so great! Thanks Mark!

  17. I feel best when I’ve had my morning coffee with cream then do any type of workout (weights, HIIT, walking, sprinting). I seem to have plenty of energy and don’t bonk. I mostly started doing my routine this way because I would always get nauseous when I worked out with food in my stomach. I’m usually working out anywhere between 12-14 hours fasted and then I seem to wait to eat until after I’ve cleaned up, maybe 30-45 minutes after I’m done with the workout. If I’m doing a long, strenuous activity for the day, say snowmobiling, I’ve found I need to eat before I attack a heavy physical day like that or I absolutely bonk. Great article!

  18. Sir, is it viable to do the fasted and fed training on a micro level? Eg: one week fasted training then following week go for PB? , then continue this on a weekly basis. Would one week fasted be enough for metabolic adaption or even say 3 weeks fasted?

  19. I personally have found that a brisk walk on an empty stomach in the morning works quite well for me. Two to three days a week I walk 30 minutes to my work place (an office job) and effectively do a 16 hour fast. 16 hours for whatever reason appears to be the sweet spot for me. Very easy to do with no side effects. If I push the fast to about 18 hours, I find that I often start to feel a bit of brain fog and my thinking seems to get a bit slower, so I tend not to do that if I can help it.

    I have never tried fasting and doing a high intensity workout. I suspect it would be much harder than a brisk walk.

    I find it interesting that people are asking about drinking coffee in a fasted state. I have tried it, but it’s something that I can’t do. I find I get terrible nausea and feel shaky. Perhaps I am not very well caffeine adapted 😉

  20. I seem to feel better when I train fasted. I will eat a salad at lunch then nothing the rest of the day and my martial arts classes are at 7:00 pm. 62 yrs old so I’m not a competing athlete , i do work 10 hr days in my business, I can also go sometime after a workout not eating without any problem. I’ve been a fat burner since and before your book came out. It’s worked well for me. Thank you for all you do

  21. Really interesting topic, Mark!

    I usually train in a fasted state, within an hour or two of waking up.

    Just to clarify, about how many hours are you considering fasting to be?

    Also, please share your thoughts on coffee pre/post workout. How would you reconcile morning coffee and fasted training? I like the idea of coffee as a part of a morning routine to wake up and start the day, whereas training first thing raises adrenaline and alertness, making me less inclined toward coffee.

  22. Interested in any documentation on whether MENOPAUSAL women respond to intermittent fasting & fasted exercise more like men, and get better benefit than pre-menopausal.

    1. Great question. So little research for menopausal women and the hormonal chaos we endure.

  23. I haven’t been a breakfast person in years; I ride a bike 14 miles to work in the morning and then back home at the end of the work day. The morning ride for me is so pleasant and easy and meditative. Lately I’ve been dabbling with skipping lunch as well as breakfast and when I do this I have found, surprisingly, that the the ride home, which is normally a bit of a slog (dark, hilly) is EASIER (less energy lull, less taxing, more capable on hills) than it is when I eat lunch. I also find that when I skip lunch and ride home I’m LESS hungry when I get there than if I’d eaten lunch.

  24. I primarily train while fasted. I get up around 5:30am and do the Simple & Sinister kettle bell workout. This is a series of 10 x 10 swings with a target of completing them within 5m. It’s essentially a HIIT.

    After the swings, I do 5 turkish getups each side, nice and slow. This takes another 5m.

    Then I do my Heavy Hands workout for 20m on weekdays and 45m on the weekend. No days off.

    I’m done by 6:10 so I cool down with some stretches (mostly hip, hip flexor, and related).

    I don’t eat until noon (usually).

    This routine helps me maintain around 12% body fat. As a 46 year old male, I’m pretty content with that. And the kettle bell HIIT has been the most effective approach to increasing my VO2MAX, lowering resting heart rate, etc. that I’ve personally encountered. Between that and Heavy Hands, my heart is in great shape.

  25. WRT fasted training and weight loss…

    The study you refer to behaves the way one would expect, but it doesn’t really test fasted training.

    The test should be ad libitum comparing the fasted workout to one with a meal ahead of time. I’m betting that the fasted workout will result in less overall food intake.

    Personally, I can do 3 hours on the bike pretty easily these days; 4 hours I tend to get hungry.

  26. Dear Mark,

    You write: ” Before heavy lifting or HIIT sessions, however, I’ll drink 20 grams of collagen peptides with some ketone salts and often creatine monohydrate. ”

    Could you please explain which product or products you typically use? In which quantity?

    Thanks a lot in advance.

  27. Have to read this fully later – skimming stuff.
    How about incorporating cold fasted workouts?

  28. I am surprised that in the fat loss section you did not mention the biggest reason that I make sure to do at least some aerobic exercise in a fasted state… Exercise in a fasted state will provide a greater increase in your insulin sensitivity. Which, of course, can make a huge difference in fat loss!!
    Also, I always took my noon run before eating anything, so that I would not end up feeling nauseous…
    I first learned the fact that fasted exercise makes a bigger impact on insulin sensitivity in “Just Ride” by Grant Petersen. In that book, Petersen’s simple summary of the inter-relationship of diet, exercise, and weight loss is one of the best I have ever read.
    Other than that, today’s blog is full of interesting information!

  29. Virtually of my morning workouts are performed in a fasted state, and have been for over 10 years. Anything up to 90 minutes of low intensity aerobic work just feels better without consuming calories beforehand. If I am uncertain about the duration (i.e. exploring a new trail), I will often carry a handful of nuts or a couple of dates (as a rescue snack). I never set out to do anything other than what felt best for me and my body, and it’s worked well for me. Even in my heavy carb eating days, this fasted training helped me to maintain some level of fat burning capacity to avoid constant sugar intake.

  30. My buddy and I just finished a 10 mile obstacle course race in GA in a completely fasted state and performed and felt great. We train fasted, are fat adapted and in ketosis always. Anytime I eat prior to a workout I always end up saying afterwards, I shouldn’t have eaten. The “feeling” of training fasted and not eating after a workout is its own high. Thanks mark.

  31. For what it’s worth, It’s my understanding that Mark Mattson, professor of neuroscience at the National Institute Of Aging (and a rock star in the fasting universe) runs 6 miles 14 – 16 hours into a daily fast. He’s published more research than I can ever read so I think he knows what he’s doing. He starts many comments with the preface “From the perspective of evolution…”

  32. I crossfit 3x/week fasted (black coffee only) and surf fasted about 2x per week; both in the morning. I usually eat my first meal at around 11am, which is a large, high protein, eggs/omelet/leftover meat combo.

    I’ve lowered my carbs in the past few months by eliminating fruit and starches. After an adjustment period, my workouts are now going well; particularly the longer ones (20min +). I like a longer warmup, but seem to have more consistent energy once I find the rhythm, tempo of the workout.

    I’m 45, but identify as a 25 year old. haha. I’m going to stick with this for a while and see what happens.

  33. This is a very timely article as I’ve been questioning whether continuing the fast _after_ is advisable.

    I’ve always been a morning exercise person and never been able to exercise after eating so I’m always exercising fasted.

    But now I want to fast up to midday and I wasn’t sure if that was a good idea – thanks for adding the detail I needed on fasting afterwards Mark!

  34. Does coffee before an early morning workout (done maybe an hour later) change any of these points you brought up? Those would be my fasted mornings…coffee, then workouts with amino acids, usually finishing with some kind of short bursts, then another couple of hours before I have some food. I do this regularly. Should I be mixing it up more often to keep my system on it’s ‘toes’? My bigger days may start with hi fat coffee (swim to SUP to bike to running short hill sprints to lawn work…then eat!) because I’m not really ready to go for 4hrs and up without that slow burning top off in the morning.

    Keep up the great work! Thanks for all the help you are throwing out to us!

  35. I’ve read some scientific tests that state fasted training doesn’t increase overall fat loss, but does increase fat lost from stubborn areas of low blood flow (belly, thighs, obliques). What’s more if whilst fasted you take a supplement yohimbine, it shuts off the negative alpha receptors in these stubborn area’s. So fasted + yohimbine = more blood flow die catecholamines to travel and latch on to receptors, and fat receptors very willing to release fat. I think fasted is much more beneficial than fed, I’ve personally seen better results (I’d say it feels quicker but maybe just where the offset of additional fat in stubborn area’s is actually reduced).

    1. Interesting. Yohimbine is quite powerful and if I recall correctly care must be taken if you are on an MAOI. In my reading I believe that most of the benefits of training fasted come from 3 things:

      1) Hormone-sensitive lipase that mobilizes fatty acids for use

      2) Low-insulin levels which are necessary for the above to operate.

      3) An amplification cascade caused by norepinephrine to empty the cell of glucose.

  36. Hi, Mark, and thanks for your blog.
    I workout at 6 AM, so my window to eat is from 1 to 9PM.
    I usually sip on BCAA during my workout and during my fasted time, but I have an important doubt in order not to lose muscle:
    Will I be doing any harm by not drinking my protein shake after working out?
    Thanks in advanced

    1. Choose EAAs instead of BCAAs. They provoke less of an insulin response and are the full spectrum of essential amino acids — providing your muscles with important building blocks.

      From the research I’ve read, when training fasted you are better off eating/drinking your protein shake after working out.

      If I were in your boat I would still wait for ~2 hours before refeeding.

  37. ” Going a few more hours without eating enhances the HGH response, which helps spare muscle burning and augments the adaptive responses.” I’d like to find scientific evidence of this. Do you know of any papers?