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Training on an Empty Stomach: A Low Heartrate Alternative?

Posted by on Jul 2, 2012 | 24 Comments

Many of my ultra friends have started experimenting with low heart rate training. The technique is based on the idea that we can train our body to run faster while remaining in an aerobic zone (burning fat versus carbs as a primary fuel). Many people have had success with the method. I’ve played around with the idea, but found the long, slow running to be too boring. It took the fun out of running.

For years, I’ve used a different technique that accomplishes a similar task. I purposely fast about 12-24 hours before some of my long runs, then do not eat during the run. This forces glycogen depletion very early in the run- my body burns it’s available stockpile of carbs. At first, the crash is severe. It’s what marathoners like to call “the wall.” My average pace decreases dramatically and I feel terrible. After a few such runs, the crash becomes a lot less severe and I’m able to maintain a much faster post-crash pace. Furthermore, the subjective feeling evolves from “horrible” to “eh, this isn’t too bad.” In essence, I’m training my body to deal with glycogen depletion and utilize fat as a primary fuel source.

With low heart rate training, the goal is to increase your aerobic pace to decrease finish times. This works well if you remain under that aerobic threshold, or the point where your body is using mostly fat as fuel, for the entire race. Personally I don’t like to have that limitation. I like the freedom of adjusting my pace based on how I feel, the terrain, available food, competition… whatever.

Low heart rate training teaches your body to utilize fat as a fuel, which allows you to run faster while using more fat and less glycogen. Regularly training on an empty stomach does something similar. Check out these articles:

Piece of evidence #1:

Piece of evidence #2:

The Elite Question

People sometimes ask how elite ultrarunners run races while consuming very little food. Here’s an example. At Bighorn a few weeks ago, Damian Stoy, the 50 mile overall winner, ran the race on three gels. That’s roughly 300 calories. He would have burned between 5000-6000 calories for the entire race. Assuming he started with about 2000 calories worth of glycogen (stored in muscles and the liver), he would have had at least a 2700 calorie deficit over the course of the race. Most of that 2700 calories had to come from fat.

How is it he could have maintained a winning pace (9:22) over rugged terrain with lots of climbing while fighting a glycogen deficit? he had to rely on fat as fuel. But he clearly wasn’t running below his aerobic threshold (he was breathing hard when he passed me).

I would hypothesize he does what most fast runners tend to do- eat very little before and during training runs.

What Would I Recommend?

Low heart rate training is an invaluable tool… for building a good endurance base. The low intensity dramatically decreases recovery time and limits the occurrence of injuries. I highly recommend new runners use the method to build an endurance base regardless of your goal distances.

Once you build that base, however, low heart rate training is of little value. The slow pace will limit your speed. Doing speedwork like fartlek runs, tempo runs, and interval training will help make you faster. If you’re planning to run anything over a half marathon, adding foodless training will continue to develop your ability to use fat as fuel. This will limit the negative effects of the “wall” that cripples so many runners.

 Let’s look at a typical marathoner. Most marathon training plans top out at around 20-22 mile long runs. If a marathoner eats before a long run of that distance, it’s unlikely they will experience glycogen depletion during training. When running the actual race, they cross that line of glycogen depletion during those last few miles. Since it’s something their body rarely if ever experiences, it hits hard. Really, really hard.

They could eliminate this problem using a few methods:

1. Run the entire race below their aerobic threshold so they burn mostly fat. This would be the strategy recommended by the low heart rate crowd. The problem- you’re forced to stay below that threshold or you’ll hit ‘the wall.”

2. Eat enough to cover the deficit. In the case of a marathon, consuming 300-800 calories before or during the race will be enough to supply enough calories to cover that deficit. Personally I like this strategy, but it will fail if you can’t eat.

3. Train to run despite the wall. By training regularly on an empty stomach and purposely hitting the wall, you’ll limit the negative effects of glycogen depletion.

The best-case scenario would be to utilize all three. Build an endurance base using low heart rate training, During the race, eat if you can. If you can’t, your foodless training will guarantee performance won’t be impeded by a glycogen crash.

The Actual Training

I try to use this method at least twice per week. It’s pretty easy- just run long enough to deplete your glycogen stores. The longer you fast before your run, the earlier you’ll crash. If I eat immediately before a run, I’ll usually hit the wall around mile 18-20. If I fast for 12 hours, it usually hits around 13-15. If I fast for 24 hours, I may hit the wall within the first 5-8 miles. Your results will vary. Once you hit the crash, continue running for a few miles. I aim for about four to five miles.

The first few times are going to be awful. Your pace will decrease dramatically. You’ll feel drained. Stuff will hurt. You’ll probably feel depressed. Don’t worry- all of these symptoms will ease after a few training sessions. Eventually the “crash” barely registers. Furthermore, each subsequent crash experienced in the same run is lessened. In an ultra, this is important because most people decide to drop from races while in the middle of an especially bad low point. Make the low points more tolerable and your finish rate increases.

This method also teaches you to predict when glycogen depletion is about to occur. You’ll learn the subtle, often-missed early signs. In a race, these signs can be used as a cue to eat something, thus preventing the crash before it becomes worse.

I like to do these training sessions a few months before my goal race. Four or five sessions seems to produce good results. Eight to ten sessions seems to maximize the effect.


Training on an empty stomach can be an invaluable tool to your training if you plan to run longer races. It’s not difficult (though mildly unpleasant in the beginning). The potential benefits can be huge as it frees you from the shackles of maintaining an aerobic-zone pace and regular food consumption. Personally this method has been instrumental in my own training for 100 mile races.

What do you think? Do any of you do this now? Will you add it to your training regimen?






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  1. Greg Arwood
    July 8, 2012

    This information has been around for years. Professional Cyclist have used this method too drop weight, and teach you body to burn fat. It also prepares you mentally when you hit the wall on how to push through. The key to the method is that it is all about the heart rate. It must be kept low.

  2. Wild Runner
    July 6, 2012

    Hi Jason

    I have had quite a bit of success with low heart rate training, using the Maffetone method. I went from running 11:30 min miles at 137bpm down to 9:30 min miles at the same heart rate in a couple of months. I agree that the slow speed in not always that fun, and if you live in a hilly area, a treadmill is an effective method, again, takes away a lot of the fun of getting outside.

    I have found that training fasted has a good effect for me, not just running, but when doing resistance training too. I tend to fast overnight and then do a training session at midday or so, go home, and then eat. I find that my energy levels are much higher fasted, would seem like a contradiction but it works well for me. Cheers

  3. Jennifer P
    July 3, 2012

    I’ve read a few other bloggers that use this method, and I won’t lie – it terrifies me. I’m the first to admit that I overeat before, during and after runs because I am terrified of hitting the wall.

    As a mid-back of the pack trail runner who runs mostly 25K races, is there a benefit to giving this a shot?

  4. Rand
    July 3, 2012

    Great post, I have been struggling with the aerobic zone training thing for a few months now and getting no where – actually getting slower, and less interested in running all together. At the same time I have been reading about fasting (see Brad Pilon’s ebook Eat Stop Eat). Good stuff, both experiences seem to support what you are saying here. Thanks for giving me permission to run again and not feel guilty about ditching the Aerobic zone now and then!

  5. Barefoot Running University » Gluttony Training: The Other Side of the Fasting Training Coin
    July 3, 2012

    […] the Fasting Training Coin Posted by Jason on Jul 3, 2012 | No Comments Yesterday I wrote about fasting as a method of training. Learning to eat before and during the run is another useful training […]

  6. Ryan Banfield
    July 3, 2012

    I almost always eat lowish carb, and I train a lot. Run at lunch, sometimes high intensity at night+resistance. I find running on an empty stomach to be the most comfortable, and my runs aren’t compromised from the lack of food because I’m already adapted to low carbohydrate (glucose) in my diet. Fasts make a lot of sense too. On long endurance runs the crash can be severe if you haven’t trained yourself previously on low-carb. Once you do, you wont need that shot of Gu, or fruit so often, and you can go much longer without fatigue.

  7. Alex
    July 3, 2012

    To be blunt (and maybe rude), a lot of mid-packers’ easiest route to faster times would be to drop some pounds. And taking in less calories is, of course, the only way to do that.

  8. Kate Kift
    July 2, 2012

    My history is pretty lame, but I vaguely remember that before battle, medieval knights used to fast 12+ hours before to obtain similar results. If they fasted before battle, then any ‘crash’ would happen early on, but they could continue a long time afterwards on minimal food and water.

    Not sure how accurate that it -might be a myth. It’s a public holiday here in Canada, so I am not exactly with it.

    Also I used to think it was funny that people in my training group thought I was strange when I wouldn’t take anything with me in relation to food or drink on run’s 7 miles or less. I didn’t see or feel the need. Still don’t. I may take water on hot days, but nothing much on run’s. Even on 13 milers I may take a couple of gummy bears but that’s about it.

  9. Steve
    July 2, 2012

    Thanks for those pearls, Jason. I’ve started aerobic training as a result of reading your book. I’ll have to experiment with fasting once I’ve advanced far enough.

  10. BF in AZ
    July 2, 2012

    I haven’t tried this yet, although I have noticed that each long run I seem to require less food. When I first started marathon training a year ago I was eating a lot on long runs and still having a hard time of it. Over the months, I have gradually been eating less food, often a lot less food, and my body seems fine with it. I wonder if this means that some of the same benefits that you discuss can be achieved by gradually lowering amount of food you eat on a run. If so, this would be more pleasant than intentionally crashing a bunch of times.

  11. James woody
    July 2, 2012

    I am going to start using both techniques and see how it goes. Thanks for the blog I love it!

  12. chris
    July 2, 2012

    Good piece of advice for training. Ernst VanAaken talked about running while hungry. Good way to buiold that fat-burning endurance ultra runners require. I particularly like one comment you had:

    “In an ultra, this is important because most people decide to drop from races while in the middle of an especially bad low point. Make the low points more tolerable and your finish rate increases.”

    This is EXTREMELY true for me. When I hit those low points in an ultra (2am, 75 miles on the trails, achy, hungry, thirsty, tired, etc)…it’s easy to give up. If you experienced those lows in training–at least the glycogen lows–you’ll be prepared for them in a real race.

  13. Tuck
    July 2, 2012

    I actually have been thinking about this for quite some time. It seems logical that it would work, as being in a fasted state when fat-adapted means your body is going to be running on fats and ketones, the fuels that Maximum Aerobic Fitness training (aka low-HR training) is designed to encourage your body to burn.

    However, what seems to happen in practice is that your body will burn stored glycogen when it’s not fit enough to burn all fat for energy requirements. You can tell that this is happening when you finish a vigorous workout and you’re craving carbs. And yes, I’ve experimented with this for the last two years.

    When I went to see Phil Maffetone (one of the fellows with the most experience with low-HR training) speak, this was one of the questions I asked him, btw. He did tell me that he had a patient who went on a ketogenic diet (equivalent to fasting, from a metabolic perspective) as the low-carb initiation to the Maf program, as she was diabetic. She dropped her MAF pace from 8min/mile to 7min/mile in two weeks.

    There’s clearly a benefit to ketogenic diets and athletic performance, there’s clearly a benefit to fasted training (it induces your body to increase the size of the glycogen stores, interestingly).

    But it doesn’t induce your body to make the same adaption that MAF training will.

    “Once you build that base, however, low heart rate training is of little value.”

    This is clearly not correct. Mark Allen, for one, continued low-HR training throughout his entire career as pro triathlete. He continued improving each year, reaching his fastest MAF pace in the year he retired. His record for fastest time in the marathon portion of the Kona Triathlon still stands… He apparently did both fasted training and competition and low-HR training.

    • Jason
      July 2, 2012

      I just read your comments about AK’s training, Tuck. Seems to fit well with this idea.

      I’m not suggesting it induces the same physiological changes as MAF, only similar results. I believe a combo of the two will net the best results.

      Regarding the uselessness of MAF after the base is built- perhaps “of little value” was a poor term to use. I do think there’s a point of diminishing returns using MAF to get faster. At some point, speed work has to be introduced. I believe Allen is a proponent of that.

      The question- will non-MAF training increase MAF pace? I suspect it will, and training in a carb-depleted state will facilitate that.

      • Tuck
        July 2, 2012

        “I believe a combo of the two will net the best results.”


        “I do think there’s a point of diminishing returns using MAF to get faster. At some point, speed work has to be introduced. I believe Allen is a proponent of that.”

        Yes, you’d cycle back and forth between MAF and adding in some anaerobic training, to continue improving, as you will plateau with either approach.

        “The question- will non-MAF training increase MAF pace? I suspect it will, and training in a carb-depleted state will facilitate that.”

        I tried that for a year, and didn’t really see the same benefit that I did after I started explicitly training at the MAF pace for long periods.

  14. Jen
    July 2, 2012

    My boyfriend was trying to convince me that it would be good to train on an empty stomach, but I was a wuss about it. Thanks for giving him more ammunition. 😉

  15. Johnny boy
    July 2, 2012

    I’m a firm believer in what I call worst case scenario training. I like to go out on hot days, right at noon, not eat, not bring water, not sleep, run up all the hills in various combinations or all in one training run.

    I try to get some of this stuff into every 4th long run or so just to make sure I have good perspective on it if it hits in a race.

    Thanks Jason, good stuff!

  16. Dyay
    July 2, 2012

    This is awesome! i’m currently preparing for my first ultra 2 months from now. the low HR training really is making me nuts. this is really helpful jason. thanks mucho!

  17. Wiglaf
    July 2, 2012

    What if you just eat bacon before and during the race or training runs? Will that yield the same results?

    • Jason
      July 2, 2012

      Theoretically yes. And bacon is awesome.

      • Wilt Alston
        July 2, 2012

        …my personal experience suggests this immutable fact: If bacon doesn’t improve both your performance and your experience, you’re doing something wrong.

    • Dave
      July 2, 2012

      While on a long club run the other day, we actually were discussing the merits of bacon as a mid-run snack. I have yet to try it, but even if it doesn’t benefit my running, hey, I get to eat bacon, so that’s a win in my books.

      Having said that, it’s probably a good idea to get in a few BDRs (bacon depletion runs) leading up to a race, so that the race-day benefit of bacon can be fully realized.

      • Wiglaf
        July 2, 2012

        Excellent point! I ran a 52.4 miler a month ago. I had bacon and pickles every 13.1 miles. I also had other carb food including a half a can of red bull every 13.1 miles too, but my body had no problem whatsoever with bacon and running. It knows what’s good for it.

    • Paul
      July 9, 2012

      Interestingly enough there seems to be some evidence out there that eating foods with a higher fat concentration prior and during exercise can help increase your bodys use of fat oxidation as a source of energy. Something to do with the fats being redily available in the blood stream rather than first having to be ‘liberated’ from your stores.

      The bad news is that were talking good fats here, and not so much bacon…. although a bacon and banana on whole wheat drizzled with maple syrup certainly sounds appealing, ill probably stick with the banana and walnut version.