Don’t Make These Fueling Mistakes

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When I ran my first marathon I knew next to nothing about fueling. Oh, I did plenty of research on the internet, but still my fueling on long runs was haphazard at best. There was the time when I ate a chicken dinner 2 hours before running 16 miles and it didn’t stay down. There were times when I got light headed from inadequate fueling.

In the last few months I’ve come across some information that has revolutionized my personal fueling. I can’t take credit for coming up with these ideas. Here are some guidelines for smart fueling success:

Before Your Marathon. . .

1. Don’t “Tank” Up!
Don’t drink excessive amounts of water or fluids in the days prior to a race or long run hoping to get a “head start.” The only thing you’ll accomplish is getting more exercise by running to the bathroom frequently. Instead make it a habit to drink water consistently throughout the day. You need approximately .5-.6 of your body weight in pounds in ounces during the day (depending on weather conditions and your activity level).

2. Back Away from the Pasta!
This refers to the infamous carbohydrate loading technique. You’ll hear a lot of conflicting advice about carb loading. For me the bottom line is not to do anything radically different than what you did in training.

Think back to the most successful long runs that you had and use a similar fueling technique. Leading up to a race you don’t want to stuff yourself with extra food. Any excess food that you take in will either be passed through your digestive system or stored as body fat.

The time period for training your muscles to maximize their glycogen storing is during training. You have a one-hour window of time after each workout where your muscles are most receptive to storing glycogen (this is the time to carb load).

3. Put Down the Salt
Don’t sodium load before a race. The average person consumes approximately 6,000-8,000 mg per day which is above the recommended dosage of 2,400 mg/day. Taking in extra sodium before your race can actually disrupt the hormonal system responsible for regulating sodium and your fluid balance. Sodium is only one electrolyte that’s necessary in the body.

If you’ll be running more than 3 hours or in hot, humid conditions (or you have a history of cramping) you may want to consider a sports drink with a full profile of electrolytes or some electrolyte tablets. Be sure to practice using any electrolyte supplements before race day.

4. Don’t Pig Out the Night Before Your race
You won’t cause your body to store extra carbohydrates. The only thing you’ll actually accomplish is clogging your digestive system and causing water retention. Eat that pre-race dinner until you’re satisfied and save any indulgence foods to celebrate after the race.

5. Don’t Eat the Morning of Your Race.
Here’s more of the story on this one. If your race is over 60 minutes in length, don’t consume any calories three hours prior to the race. Eating a prerace meal at the wrong time will negatively affect how your body uses its limited supply of glycogen.

Glycogen is how your body stores fuel and it is broken down into glucose to maintain steady blood sugar levels, which controls your energy level. If you eat less than 3 hours pre-race it will stimulate an added release of insulin which will cause you to burn through your glycogen more quickly.

Even though your stomach may be empty in the morning, your muscles still have their full supply of glycogen on board. The only thing that eating a pre-race meal does (besides filling your stomach) is to top off the glycogen supply in your liver (which is tapped into during your night’s fast).

Don’t sacrifice sleep to eat. If the thought of waking up at 3- 4am to eat sounds nauseating, a better strategy may be to consume 1-2 energy gels 5-10 minutes before the start of the marathon. This will top off the liver glycogen stores nicely, which is the goal of the pre-race meal. It will also provide some calories to increase muscle stores at the beginning of exercise without negatively affecting how muscle glycogen is used.

During Your Marathon. . .

1. Don’t Guzzle Fluids During the Race.
Keep your fluid intake between 16-28 oz per hour. Research shows that having a consistent fluid intake over 30 oz/hour increases your risk for dilutional hyponatremia, which is diluted sodium levels in the body. A recent study suggests only drinking when thirsty. Too much fluid consumption can be fatal.

The body knows that it can’t take in as much fluid as it’s excreting during exercise. If you try to match output with intake while running you’ll overload your system. Drink to replenish, not replace lost fluid. Have a plan for fluid replenishment and listen to your body.

2. Remember Less is Best
Maybe you’ve heard that the average runner burns 100 calories/mile. Doing some quick calculation you realize that approximately 2,600 calories are burned during the course of a full marathon. Don’t follow a calories in/calories out approach. Your body simply can’t handle this level of calorie replacement and will react with bloating, nausea, vomiting, or diarrhea.

Just like with hydration, try to fuel to replenish, not replace. The best approach is to replenish calories at a rate that your body can assimilate them while allowing your fat stores to make up the difference. It’s important to keep blood sugar levels stable through calorie replenishment, but not worry about the calorie deficit that you create. A good guideline to follow is taking in approximately 200-280 cal/hour.

3. Not All Sugars are Created Equal
Simple sugars (like glucose, sucrose, fructose, etc.) are not ideal fuels for exercise and they’re health hazards when consumed regularly in your normal diet. These simple sugars give you energy peaks and crashes and are not absorbed very efficiently by the body. They need to be mixed in weak concentrations of 6-8% for efficient digestion, which means you can only take in about 100 calories/hour. You can consume more, but you can’t absorb more. You’ll only get sick trying.

Complex carbohydrates, however, absorb at about three times the rate as simple sugars. You’ll also avoid the “highs and lows” so common with simple sugars and get steady, reliable energy.

4. Don’t Sacrifice Muscle
When exercise extends beyond about two to three hours, your body begins to rely on some protein to fulfill its energy requirements. If you fail to include protein in your fuel, your body has only one other choice: your own muscle! This process is called “lean muscle tissue catabolism.” When your body starts using its own muscle tissue it hinders performance and increases fatigue.

Here are some observations that Hammer Nutrition has made over the last 23 years on fueling success and failure: *Note, the above link is our affiliate link. Our referral number will save you %15.

Fueling Success
Under 30 fluid oz/hr
Sodium intake between 300-600 mg/hr
Calorie intake less than 280 cal/hr
Minimal simple sugar intake, complex carbs
Body weight at finish decreased no more than 2-3%

Fueling Failure
Over 30 oz/hr
Sodium intake over 600 mg/hr
Calorie intake over 300 cal/hr
Simple sugar based fuels= stomach problems
Dehydration or weight gain


This has been a rather lengthy post but it is hard to re-educate ourselves without dealing thoroughly with these topics. In the near future we plan to have a fueling expert on the podcast. Stay tuned! -Angie

40 Responses to Don’t Make These Fueling Mistakes

  1. Trevor September 20, 2011 at 11:47 am #

    I think I’m finally getting a grasp on this whole simple sugars verses complex carbohydrate thing. I tried Hammer’s perpetuem solids on my 18 miler. They tasted like chalk with a hint of latte. The boost in energy without the crash was great!

  2. Hayley September 20, 2011 at 2:13 pm #

    The energy gels that you refer to for pre-race — are those like the gooey ones (like the Shot Gel) or are you talking about the gummy-like chews?

    And what kind of complex carb do you recommend for during the race?

    • Angie September 20, 2011 at 9:12 pm #

      Hi Haley,
      I prefer the Hammer gels pre-race (they have a gooey type consistancy but are easier to get down than GU). Hammer gels are made with maltodextrin which is a complex carb. I also use Perpetuem Solids (more of a chewable consistency) for runs over 3 hours. They contain the right combination of complex carbs and protein. I’ve seen the best results this way.

  3. Danny September 20, 2011 at 3:48 pm #

    Are gels and drinks, such as those by Lucozade or Poweraid, simple or complex carbs?

    Also, elsewhere on here, I think, I read a post recommending runners eat if they are running for over an hour. Does this advice hold true but the caveat is at least 3 hours before the race with a drink or gel to ‘top-up’ if not eating?

    I think I’m totally confused now!

    • Angie September 20, 2011 at 9:22 pm #

      Hi Danny,

      I’m not familiar with Lucozade, but I know that Poweraid contains only simple sugars. You can look at the label and find out fairly easily. It will say for example: carbohydrates 23g
      sugars 23g If the label reads this way and the ingredients list sucrose, dextrose, fructose, any ose you know that you’re dealing with a simple sugar.

      I definitely don’t want to spread more confusion about whether to eat or not before running. Simply put, I’ve changed my recommendations about eating before a run greater than 90 minutes. If you’ll be running/racing for more than 90 minutes make sure that if you eat you do so at least 3 hours before you start. This will allow for proper digestion and not negatively affect how rapidly your body uses its stored glycogen. If you have a morning race and don’t want to get up that early to eat and digest, simply have 1-2 energy gels 5-10 minutes before your race. This will top off your liver glycogen levels and give you needed energy to get started.

      Hopefully this helps to clarify!

  4. Stephanie September 20, 2011 at 7:34 pm #

    I am about to run my third marathon this year- and, after my 20 mile training run, finally realized what people are referring to when they say, “GI distress”. Wow, started the run completely dehydrated and although I ran it smooth and strong, the rest of the day and evening were spent trying to recover. Ouch. Thanks for the good advice.

    • Angie September 20, 2011 at 9:24 pm #

      Hi Stephanie,

      It’s exciting to hear that you’ll be doing your third marathon soon. It’s not so wonderful to hear about the GI distress. Not fun! This often results from an intake of too many simple sugars during running. I hope that you’re able to have many more great long runs (without the GI problems)!

  5. Trevor C September 21, 2011 at 1:51 pm #

    A well timed podcast.

    I just finished the Army 1/2 in Ottawa a couple days ago and was looking for information on fueling. I started to wobble at about 18k and lost a few minutes over the final 3k. On the bus home I talked with an ultra-marathoner and he said my issue was probably lack of steady fuel.

    Instead of fueling at regular intervals I was just taking in a bit of Gu when I felt like it. Setting an alarm (time or dist) on my Garmin is probably a better idea so I don’t wait until it is too late and then bonk during the end of the race. I also plan to experiment with the amount of calories to see what works.

    On the plus side I beat my old time by 10 minutes.

    • Angie September 21, 2011 at 10:01 pm #

      Hey Trevor,

      Great job with your recent 1/2 marathon. It’s always fun to PR. These races are also a wonderful way to start figuring out your fueling strategy. It’s important to take in around 200-280 calories/hour and space it out in a manner that gives you steady energy. Keep up the good work!

  6. Sarah September 21, 2011 at 5:21 pm #

    Can you suggest a protein source that I can buy in stores? I have only one long long run before my race and can’t get Pepetuem in time to try it out sufficiently.

    • Angie September 21, 2011 at 10:05 pm #

      Hey Sarah,
      I hesitate to recommend any other sources that I haven’t tried out personally. Check out this link to the dealer locator. You might be able to find a store in your area that carries the Hammer products (cycling shops often have the products too). I know that they also do faster shipping options if you want to pay extra postage. Hope that helps!

  7. alex September 22, 2011 at 10:34 am #

    Awsome show. And thanks so much for the information you posted on your site. I just finished my first ultra marathon. I know that I need to work on my diet during training and leading up to a race. My wife and I really enjoy your show. I plan to listen to this again and save it for future reference. I have been wanting to try hammer products I plan to check out there site and look foreword to your interview with them.

    • Angie September 24, 2011 at 10:18 am #

      Hi Alex, I’m glad that you’re enjoying the podcast. Congratulations on finishing your first ultra. I enjoyed reading about your experience. I’d definitely encourage you to check out the Hammer products. They have a couple fuels designed for long events (Perpetuem and Sustained Energy). They also have great customer service. Use our referral code (186409) and you’ll save 15%. Keep up the great work!

  8. Erin Avery September 26, 2011 at 7:50 pm #

    Hi Angie,
    I’m a big fan of the show. It’s a great source of motivation and entertainment during my runs and commutes. Your recommendation in this episode to not eat before a longer race or run blew my mind. I find the idea fascinating, but I’m curious to understand the physiology of it better. Can you recommend a source for this recommendation that could provide more detail? I thought that glycogen burning was slowed in the presence of insulin, rather than sped up, since the body knows that there is incoming glucose. I definitely want to try this, and it would certainly make race day mornings a lot easier to “stomach”. Thanks

  9. Jeff September 29, 2011 at 4:05 pm #

    I’ve been listening to the show the past couple months as I prepare for the Marine Corp Marathon. This particular episode on fueling was great as I have had problems in my past 2 marathons with proper eating, race day gels, etc. I am going to try the Hammer Pertetuem next week on my 20 miler.
    Keep up the good work! Thanks

    • Angie September 29, 2011 at 7:16 pm #

      Hi Jeff. It’s exciting that you’ll be doing the MCM soon. Hammer Perpetuem has really made a difference in keeping my energy stable during long runs (while avoiding stomach problems). I’ll be using the Perpetuem Solids during the Wineglass Marathon this weekend. I hope that you have a great 20 miler!

      • Jeff October 9, 2011 at 10:57 am #

        Hi Angie, I used Hammer Perpetuem this past week on my final 20 miler before MCM and it worked great. No stomach issues and did not “hit the wall” or “bonk”. Even had enough energy to mow the lawn later that day. I will be taking the Hammer Perpetuem with me to MCM. Thanks for all your advice and help!

  10. Mallory November 7, 2011 at 2:44 pm #

    I looked on the Hammer website and can’t find where the little individual gels are. I only saw the big bottles. Will I have to buy one of those kits?

    • Angie November 7, 2011 at 2:53 pm #

      Hey Mallory. You can buy a gel sampler pack (all nine single serving flavors). If you want to order a specific single serving flavor you just have to select “single serving” when it asks for serving size. Once you select the serving it will ask you about the flavor and quantity. Hope that helps.

  11. Mallory November 17, 2011 at 11:23 am #

    I have good news! I ran 12 miles this Saturday without eating breakfast just like this site recommends. I have to admit–I was scared and a little leery at first. I drank some coffee an hour before I headed out. I halved a bag of candy and ate every hour. Plus, I drank around 6-8 ounces of Gatordade to wash down the candy. I finished my twelve faster than I finished my eleven the week before. It was under 2 hours, and I’m happy about that! I had more energy, my legs didn’t hurt towards the end like normal. I’m now a believer! I have a 10k race this weekend. I’ve always heard that glycogen burns faster when you’re going at a faster speed. Am I going to end up feeling weak if I don’t eat prior? Thanks again!

    • Angie November 18, 2011 at 10:32 pm #

      Hi Mallory. Great job with your 12 miler! I’m glad to hear that your fueling strategy worked well. I can’t say that I totally endorse fueling with candy and Gatorade, but it sounds like you’re getting on the right track.

      If you’ll be running for less than 90 minutes you can eat beforehand (leaving time for digestion) and your glycogen supply should be adequate. If you eat less than 3 hours before the race it will cause the glycogen to burn more quickly, but you should still have around a 90 minute supply. All the best!

  12. Brian March 25, 2012 at 6:34 pm #

    I am just testing Hammer products (endurolytes and their gel). So far so good their gel sure is smooth compared to GU.

    My last marathon I cramped up bad in my quads, 1 leg at mile 14 and the other at 16. I started ro run/walk then shortly after 21 I was forced to walk the rest of the way. My fluid intake was good along with the GU every 45min. Sure wish I knew what happen being it never happen in training.

    Any other thoughts?

    • Angie March 27, 2012 at 12:20 pm #

      Hi Brian. It’s good to hear that you’re testing some Hammer products. It sounds like your cramping may have been caused by an electrolyte definiency. You may need to take a couple Endurolytes before a race as well as every hour for the duration of the marathon. Each person’s body responds a little differently. I’d also encourage you to try the Perpetuem. It has a great combination of carbs and protein to spare muscle during endurance events. Good luck!

  13. Brian March 27, 2012 at 7:19 pm #

    Thank you for the response Angie.

    Can you take Perpetuem and Hammer Gel durring runs?

    • Angie March 29, 2012 at 8:02 pm #

      @Brian- Yes, both Perpetuem and Hammer gels work great during runs. Here’s an example of how I fuel for a long run: I don’t eat before a morning run then I have 1 gel and 2 Endurolytes 5 minutes before my run. I eat 2-3 Perpetuem solids every 20-30 minutes for the duration of my run. You can throw in another gel or two into the equation for some variety. I also take two Endurolytes every hour during a long run and wash it all down with water. A person’s fuel needs will vary based on their exertion, body weight, and the environmental conditions. However, the average runner can digest 200-240 calories/hour while running along with 20-24 oz of water. Hope that helps!

      • Dora May 12, 2016 at 10:48 pm #

        Angie, I am running my second marathon on June I tried Perpeteum powder in water and it worked but carrying it was inconvenient. I am planning to try Perpetuem solids in my second half part of 20 miles next week. I am drinking powerade the first half.
        Do I need the same amount of water (16 oz per hours)? Do I dissolve the Endurolytes tables in water or can I chew them and drink water right after?
        Thank you

        • Angie Spencer May 13, 2016 at 9:07 am #

          I hope the Perpeteum Solids work well for your long run next weekend. They’re definitely a bit easier to carry. Most people need approximately 16-24 oz of total fluid per hour of running (so this would include your PowerAde and any water you consumed). The Perpetuem Solids do have a bit of a chalky aftertaste so washing them down with water can be very helpful. If you have the Endurolyte capsules it’s very easy just to swallow them down with water. However, if you have the Endurolyte Fizz (the tablets) you’ll need to dissolve them in at least a little water. I’m guessing that they could possibly be chewed although I’ve never tried it before. Good luck!

  14. Cyndi June 5, 2012 at 10:23 pm #

    I’m curious about what kind of running belt you are using. My struggle is how to carry my iPhone (for safety & I love the Runmeter app), gels, Edurolytes, solids, water, etc… I wish I could just tie up the laces and go, but as my distances increase, I have to take more and more with me. I would love to hear your strategies on this.

  15. Angie June 13, 2012 at 5:09 pm #

    Hi Cyndi. It does get to be a challenge to carry all the needed running accessories. I’d suggest that you use a waterproof armband for your iPhone. I use hand-held water bottles (Nathan quickdraw elite) and carry fuels in either a SPI belt or my Race Ready shorts. I often make a loop on long runs to pick up more water or stash it along my route.

  16. Vanessa August 28, 2012 at 8:13 pm #

    I re-listened to this podcast on my 12 mile run last weekend and it was so helpful! I am new to running (and any sort of activity that requires consuming fuel while doing it!). I am training for my first marathon on October 28 – the Marine Corp Marathon in DC.

    I tried the no eating before a long run plan that you’ve mentioned a few times on your podcasts. Like Trevor, coffee is a must, but I did half a cup only 🙂 I had a couple of GU chews before I left and used sport beans on the run. When I got home I read the package on the beans and realized they were pretty high in sugar so I am thinking they are not the best choice.

    My challenge has been trying to find appropriate fuels based on your recommendations that are soy free. I am allergic to soy, peanuts, and tree nuts. Any suggestions for protein/complex carb fuels that don’t have these? Hammer Gel doesn’t have soy, but Perpetuem does. Can I get away with just using the Gel on 2 hour+ runs? Thanks!

    • Angie August 28, 2012 at 8:28 pm #

      Hi Vanessa. It’s exciting to hear that you’re training for your first marathon. It sounds like you do have a few challenges in finding good fueling products with your allergies. You can use just Hammer Gel for a marathon, although you will lose a little muscle tissue in the process. What I’d recommend that you do is to call Hammer and talk to a customer service rep. They are very helpful and have probably run into this situation before. Good luck!

      • Vanessa August 29, 2012 at 11:41 am #

        Hi Angie – I called Hammer and they were very helpful. They suggested using brown rice protein mixed with HEED. She sent me some recipes from Steve Born along with some other recommendations. Super helpful people! Please let me know if you want me to forward you that information so you have it for reference.

        • Angie August 29, 2012 at 12:49 pm #

          Great! I’m glad that Hammer had some good suggestions for you. I’d love to have that info. You can email it to when you get a chance. Thanks!

  17. Adam Haesler October 5, 2012 at 5:17 am #

    Hey Angie, sounds like great advice and does seem to still translate to my own long runs which are above 40km. I think what was most interesting is how I found out through trial that my body wanted protein about every 3 hours, so great to find out my hypothesis about my body considering catabolism is cool.

    Thanks for the advice and have a great day, Adam.

    • Angie October 12, 2012 at 2:42 pm #

      Hi Adam. Thanks for sharing your long run fueling observation. I’m glad to hear that you’re giving your body some protien for those long runs. Keep up the great work!

  18. Sam July 16, 2013 at 2:44 am #


    Thanks for the very insightful advice. I’d be ever so grateful if you could share answers or point me to articles that can answer any of the following Ques. First, some background — I am running the NYC Marathon this Nov, goal time 3 hours. Only other marathon I have run is a rural marathon in 2009 in 2:55 — I did not follow a proper ‘training’ for that race, consumed no energy/food during the race, and relied upon the water stations (and only water!) every 3 miles or so for hydrating — in short, I ran that race without any of the tips experts advise. Since 2009 I have kept in good running shape (served 3 years in the army) and before training for NYC, ran a hilly half-marathon in 1:28 in March. For NYC this November, I want to follow proper guidelines, including hydration, energy intake, etc.

    1. Since the NYC-Mara has water stations at every mile, how often should I go for a drink (per background and 3 hr pace)?

    2. Should I drink water? Gatorade? Switch off at each water station?

    3. Energy gels — I’ve read that a gel every 30 minutes is advised (every 4-5 miles at my pace), which would mean 5-6 gels in the race. How many would you advise for a 3 hr pace?

    4. I was fascinated that you advised against eating pre-race, as every other website says to do so! Since the NYC-Mara requires waking up a good 5 hrs before the 10am start to arrive in time, would you say in this case, eating a meal 4 hours pre-start is wise? I tend to always be hungry in the morning and cannot imagine not eating for 5 hours while waiting for the start of the race!

    5. I’ve read that the golden rule is train with the hydration/energy strategy one will run with in the race. My Q is that I cannot afford to consume expensive Gatorade and Gels during my training runs (dont have budget to buy ’em). How much at risk am I putting myself by training only with water? Could including Gatorade/Gels in 2 long training runs be enough to get body accustomed pre-race day? I realize this question is somewhat conditional but still appreciate your general thoughts!

    6. Final Question! On training runs, I always always increase my pace or even sprint up hills, a habit instilled from the army, an ol’ running buddy, etc. I’ve read that it is crucial in a race to maintain pace up hills and not waste energy going faster. Does this mean I need to change up my years-long training approach to hill running?

  19. Trevor Spencer March 16, 2014 at 11:40 pm #

    Here’s my answer to Sam’s questions for all you future readers coming to this page.

    (1) Always drink to thirst. Which simply means when you feel thirsty take a few small sips.
    (2) Always use the fluids that you have practiced with on your long runs
    (3) Yes, a gel every 30 minutes would equal to about 180 calories per hour. Not bad.
    (4) Yes, if you are getting up 5 hours before the race then by all means have some breakfast. You will have plenty of time to digest.
    (5) Bite the bullet and get yourself some proper fuel to train with. No, water will not be enough. You need some calories. If you can’t afford gels then bring some real food along. I know runners who fuel with yams (not me)!
    (6) Pace yourself carefully during the first half. Conserve your energy. You can charge the hills during the last 10 miles or so.

    Thanks for the questions!

  20. Sheree Dickinson August 26, 2017 at 12:39 am #

    Hi I am currently training for my first marathon. I’ve run 3 halves and would love to conquer the full. I’ve set aside 18 weeks to train. I’m at week 13. So far distance wise I’ve covered 27kms. I felt quite good. While I’m not the fastest runner I enjoy it while I’m out there.
    I’ve been using GU chews and shotz electrolyte drink, without much problem. Taking the chews every 7km or roughly 45mins. Plus drinking from 5km onwards, taking a sip or two every km.That was until I attempted to run 30km. I’ve made it to about 8-10km and been struck down by a very upset stomach. I tried the 30km again this morning with the same results, making it only to 16km before I could run no further due to diarrhea. My other 3 weekly training runs are without problems. Could it be that the GU chews and electrolytes are too much? Should I only be drinking the electrolytes and skip the chews? Any info would be appreciated. I’ve started to get a bit disheartened. After all the training I’ve put in I really want to achieve my goal of finishing.

    • Angie Spencer August 27, 2017 at 12:57 pm #

      Hi Sheree, It’s awesome to hear that you’re training for your first marathon. It’s good that you’re experimenting with fueling so that you have a good system down by race day. It’s very likely that you’re being affected by one of the sweeteners in the GU chews or electrolyte drink resulting in the GI distress. You may want to switch to a fueling method that’s a bit easier on the stomach. Many people swear by Tailwind and we use Generation UCAN (since most traditional fueling methods make me sick to my stomach). The nice thing about UCAN is that most people typically need less fuel and the result is stable energy levels. You can use promo code MTASPARTAN if you want to try UCAN out: Wishing you all the best!

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