Marathon Success – 6 Key Variables You Need To Consider

Wurtele guyUnderstanding a few key fueling concepts can be the difference between having a great marathon and not even making it to the finish.

Everybody is different, so it’s important how to customize an individual fueling plan to ensure race-day success.   It can take months of preparation to properly prepare for a marathon, and failing to understand a couple key nutrition tips is often what prevents someone from reaching their true potential.  Taking a little time to research, plan, test, and fine-tune your nutrition throughout all your training will significantly improve your marathon-day success.

This article will give you a starting point which you should adjust as necessary based on these six variables: body size, athletic background, total duration, pace, conditions, and training habits.

Consider a 150-pound, trained athlete whose goal is to finish a marathon in 3.5 hours in 65 degrees.    This athlete has a background of 2-5 years racing in endurance sports.

This athlete should consume 150 calories per hour (525 calories) and 53-ounces of water.  A balance of all five electrolytes should be consumed with a target of 400mg sodium per hour.  Again, it’s important to practice and implement this nutrition plan during your long training days.

courtesy Nils Nilsen photography

courtesy Nils Nilsen photography

Body size:  Larger athletes require more caloric fuel than smaller athletes.   There is no rule of thumb here because other variables need to be considered.  However, for a trained athlete, 1-calorie per hour per pound is a good starting point.   If you’re a 200-pound athlete, you should consider 200 calories per hour.   This general rule should be adjusted considering the following variables.

Athletic background:  Aerobic training brings about physiological adaptations that take a number of years to develop.   An athlete with a long history of endurance training has developed increased vascularization, more mitochondria and is more efficient at burning fat than an athlete who has no endurance training background.   Your body has to go through the process of adapting to stress in order become more metabolically efficient at longer distances.  The goal is to train your body to spare glycogen, burn fat more efficiently and use fewer calories per hour.

Total duration:  While you only have around 2 hours of stored glycogen (fuel), you have days worth of stored fat as fuel.   Again, the goal is to train your body to spare glycogen, burn fat more efficiently and use fewer calories per hour.

Your body prefers glycogen, which is then converted to glucose as its fuel for racing.   This means if your race lasts two hours, you can just consume water.  On the other hand, if you race takes four hours, you must consume enough fuel to cover the two additional hours worth of effort.  If you race ten hours, you’ll need enough fuel to cover a minimum of eight hours of exercise.

Pace/Effort:  How hard you plan to race determines which fuel you should use. The ONLY calories that need to bereplaced during the event are glycogen calories.  Fat calories do not need to be replaced.  If you plan to run your marathon at a fast past, which requires more effort, you’ll require more glycogen and will need to increase your calorie intake per hour.  If you plan to run at a slower pace, which requires less effort, you’ll rely on more fat as fuel and you can therefore consume fewer calories per hour.

Conditions:  Whether the race day temperature is cold or hot does not affect the amount of calories you should consume, however, it does affect the amount of fluid and electrolytes you should consume.    In a hot race, total fluid consumption is critical to success and you should drink no less than 12 ounces of water for every 100 calories.  In cooler conditions the total fluid can be reduced to as little as 6 ounces for every 100 calories.   The endurance fueling article reviews this in detail.

Training habits:  Athletes who’ve trained many months or years with few calories are able to also race with fewer calories.  If much of your long distance training has been done with very few calories you will have systematically improved your metabolic efficiency.   This means you’ve successfully shifted your body’s reliance to burning fat over burning glycogen.   Details on this can be found in the low carbohydrate training article.

Summary:  How you fuel for a marathon is greatly affected by your athletic background and other key variables.   Understanding these variables allows you to fine tune your unique fueling plan to ensure success on your next marathon.   During your marathon, consume the appropriate amount of calories and fluids based on your training and you can be assured success.



For a well-trained athlete running in a cool marathon a single EFS liquid shot flask should be all the fuel that’s needed.  EFS liquid shots deliver 400 calories per flask.  Take a small sip as you enter each aid station and chase it with a few ounces of water.

EFS electrolyte drinks are also great for training and racing as they deliver 96 calories and 1160mg of electrolytes per serving.

LiquidShot berry 

14 replies
  1. Gaby Fishpaw
    Gaby Fishpaw says:

    Perfect reminders! Thank you. Topping off glycogen leading up to race day, liquid shot convenience and water I am ready for marathon success! :)

    • Robert Kunz
      Robert Kunz says:

      Many athletes do this with great success. Ultragen goes down very easily and helps top off the glycogen, amino acids, electrolytes..etc. Thanks for sharing.

      • Gaby Fishpaw
        Gaby Fishpaw says:

        Ok, that’s interesting.
        I’ve never used Ultragen for pre-run, only post. Would it be ok to do even though I’ve never included with breakfast before? Maybe shouldn’t try something so new so late?
        What about sipping EFS drink before the race. Also do that?

        • Robert Kunz
          Robert Kunz says:

          Sipping on EFS before the marathon is absolutely a great idea. In fact we recommend you have a full bottle of EFS with you from the time you have breakfast until the start of the race.

          Though there is likely little downside to having Ultragen along with breakfast before a marathon. We always recommend you try something first. Maybe you can try this on a light morning run to see how you stomach it.

  2. brian
    brian says:

    Without getting into details, it seems that Tim Noakes would recommend some alterations in this plan, mainly the so-called “critical” hydration and electrolyte recommendations made above. Most companies that market these products make similar recommendations, for obvious reasons. But, clearly, the science is simply not that clear that this stuff matters nearly as much as we are led to believe. Of course, he echos your recommendations on carbohydrate intake and, in my experience, I would er on the side of more than stated above. Like you said, though, this is pretty individual.

  3. Robert Kunz
    Robert Kunz says:

    There is scientific evidence and there is anecdotal evidence. With our recommendations we try and marry the two. Through years and years of experience working with many athletes we realize that slightly less works better. Runners notoriously train with very few carbohydrates, often running with only water. This alone causes a shift in substrate usage towards more fats and less carbohydrates. Furthermore we are talking 3-4.5 hour marathon for the vast majority which is only really a moderately long endeavor . Lastly asking athletes to push the calories further usually results in consuming bars, gels and calories that are so concentrated they don’t get absorbed or used during the event. Our recommendation, though on the lighter side, does allow for full absorption and utilization and for a strong focus on hydration.

    If the event were to last greater than 6 hours, we would shift this focus a bit more on calories.

  4. Spencer Cearnal
    Spencer Cearnal says:

    During an IronMan (9:30-45 hour guy). What are your thoughts on additional “PreRace” towards the end of the bike? The PreRace helps me to be laser focused and “amped up” ready to go but not jittery. Just wondering what some thoughts might be on more PreRace as an athlete enters the final leg of an IronMan.

  5. Robert Kunz
    Robert Kunz says:

    We recommend PreRace for efforts of 3-5 hours. In an Ironman it would be perfect to use at the end of the bike or at T2. For a marathon run you could use PreRace immediately before the start and you would benefit through the whole race.

  6. Gaby Fishpaw
    Gaby Fishpaw says:

    Marathon went great! I sipped on EFS drink before the start and with breakfast. I had 2 liquid shot flasks during the marathon and took a squirt at each aid station and chased with a cup of water. It was a cool, cloudy weather run so my hydration amounts were fine. I carried additional EFS drink in my waist pack, because I am accustomed to carrying, and only needed that additional for the last few miles when it actually did warm up more than expected. Thanks First Endurance!

  7. Mike
    Mike says:

    I am wondering what the best hydration plan would be for an ultramarathoner? My best 100-miler is about 17:45. I dropped on my last one due to dehydration/electrolyte imbalance and never want to experience that again. Thanks for any tips!

  8. Christopher Harris
    Christopher Harris says:

    I have a question about consuming a drink like EFS prior to a long race like a marathon – I thought consuming carbs would kick up my body’s use of glycogen at the beginning of the race.

    Is that true? I can see that being optimal for a 5k (speed out of the gate), but not for a marathon (need to conserve glycogen).

    I have been using First Endurance products for years – Multi-V, PreRace, Ultragen, Shots, EFS Drink….I love the entire line.


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