Fueling for a race, or just fueling for more demanding workouts can be a daunting task. We get asked all the time for nutrition tips for these events, especially leading up to a marathon/half marathon. As we are currently 3-4 months away from “marathon season”, now is a great time to establish a fueling plan. There are endless gels, Gu’s, waffles, and supplements on the market. So how should you be fueling for a race? What products are best? What diet is best?! These are questions we hear all the time, often within a week of a race. There’s also quite a bit of information about “carbo loading” and even some various diets on how to best fuel for your competition. The goal of this blog is to identify what you actually need! There will  be a mix of tips and common mistakes made with fueling, as well as some research and specifics for those who like the actual numbers/calculations! In addition, we will discuss how to actually implement these strategies!  So whether you participate in endurance sports, have your first marathon coming up,  or tenth, here are some important tips and research to consider!


Carbs are an easier fuel to burn and digest, and give us faster, more immediate energy. They are perfect for leading up to a race, or right before athletic activity. However, having a store of fats can be very useful, as oxidation of glycogen provides only ~2500 kilocalories of energy before depletion, whereas oxidation of fat provides at least 70,000–75,000 kilocalories of energy. I don’t expect many of you to remember this number by any means. But what I do want you to realize is how much more energy can be utilized from fats. Although fats are harder to digest, can upset one’s GI system, and take more effort for our bodies to tap into, they are still an important component to include in our daily diet. Athletes who chronically restrict fat to <20% of total energy are at risk of having low amounts of fat soluble vitamins and nutrients, so it is imperative not to neglect this aspect of your nutrition. However, be mindful not to consume a fat heavy diet right before a race (within a few days). 


Ultimately, making sure you are eating a balanced diet and steadily hydrating weeks leading into a race is key. While endurance athletes always hear “carbo-loading”, it is important to know that this isn’t the only key. During training blocks, especially after strengthening or more intense workouts, getting an adequate amount of protein is necessary as well. You can start carbo-loading about 2-3 days before your race, and decreasing fatty/ protein heavy meals. Do not eliminate them by any means, just have them be less of the total macronutrient intake. 


See below for daily carbohydrate requirements, and details of how to supplement, based on activity level. Right before race day will be different!

1 hour per day of exercise (Defined as 1 hour per day): 5-7 grams/kg of body weight

1-3 hours per day of exercise: 6-10 grams/kg body weight/day

4+ hours per day of exercise: 8-12 grams/kg body weight/day

For you ultramarathoners/ironman athletes out there, or those doing sustained exercise for 4+ hours, fats may be a better choice as a larger percentage  of your diet. Feel free to reach out to me regarding this topic or look more into it, as your supplementation will be different than someone preparing for a race day or two!



Carbo-loading (aka glycogen supercompensation) about 36-48 hours before your race/competition can be very helpful for races > 1.5 hours, with research demonstrating about a 2-3% improvement  in performance compared to those who do not carbo-load. A carbohydrate rich diet of at least 6 grams per kilogram of body weight is recommended, with this number increasing up to 7-12g/kg about 24 hours before. About 1-4 hours before the event, research describes “topping off”, where you have a single dose of 1-4 grams per kg body weight of carbohydrate to top off what you lost overnight! This is where little snacks like a waffle and syrup come in handy, or some performance gels if those are your preference.



The key to determining how to fuel during a race starts with identifying a few factors. First off, how long are you going to be exercising for? A systematic review found that for endurance events lasting less than 1 hour, no additional carbohydrate ingestion was required and just water consumption would suffice. However, for endurance activities that will be lasting between 1 and 2.5 hours, 30-60 grams of carbohydrate per hour is ideal in a solution (either a sports drink or combination of a gel/gu with water). For events longer than 2.5 hours, higher carbohydrate intakes, recommended at 60-70 grams per hour is recommended. To put this in perspective, about 1 energy gel every 30 mins (depends on the brand, etc). This is based on research regarding how much we can actually absorb and digest. It is okay to spread out the ingestion of these carbohydrates as well, as your body may need a few minutes in between consumption to absorb this optimally.  Up to 90 grams per hour can be associated with improved performance for these competitions, but they do come with risk of increased gastrointestinal discomfort. Your body can ingest at slightly higher rates when you provide it with multiple carbohydrate sources, which I will discuss further down in the “what fueling option is best for me?” section.



One thing that can occur leading up to a race is inconsistency with hydration, where people can overhydrate right before or right after the race. A research study highlighted that in the Boston marathon one year, “an alarming 13% of finishers had hyponatremia which was even considered an underestimation, and 0.6% (90 finishers) were critical (≤120 mmol/L)” This means they had too much water in their body and it diluted their overall blood serum levels. While I am not advocating not drinking water, just simply chugging a ton of water all at once can actually do more harm than good. 


The short answer is: YES! Caffeine has been shown in several well-designed studies and in a meta-analysis to increase the time to exhaustion in running trials and improve performance. The optimal amount was found to be about 200 to 400 mg about 1 hour before exercise. In controlled amounts, caffeine does not have the diuretic effect we once thought it does which is great news! The key is making sure your source of caffeine is something you are used to, sticking with your morning coffee routine before a race is a simple way to get it. 

However, some people will over-caffeinate which can hinder your performance (> 9 mg/KG body weight can have side effects and impede performance). The key is if you do use some gels/gu’s with caffeine in them and decide to take them pre-race, that should be enough supplementation and the ‘morning coffee’ is not necessary. 


WHICH Energy gel/Supplement is BEST?

You have to find the ones that work best for you. The key is finding ones that have both glucose and fructose mixtures, as your body can absorb more and therefore provide more energy. Some have caffeine in them, which as we discussed above can be advantageous. However, too much caffeine intake can be detrimental, so not going outside of what your body is used to or has “practiced” is not recommended. An issue many run into is that they have trouble getting the proper amount of water with the stickier gu/energy gels. For these individuals, there are some that are more liquid based and do not require water at the time of consumption. There are many endurance sports drink mixes that will provide the adequate supplementation to help fuel you going forwards!



  1. First tip is HAVE A NUTRITION PLAN! This does not have to be something super innovative or even extremely detailed. But many run into issues that have more to do with nutrition/fueling/hydration rather than their actual running. One of the most common mistakes that is made when about to run a marathon is individuals will try a new fueling option either the same week, or sometimes even the same day.  Gastrointestinal distress is real, and many can run into issues on race day if they don’t know how their body will react to a product or change in routine.
  2. Don’t change your timing when you eat: If you always eat about 2 hours before you run, you may have to wake up early on race day to accommodate this. Do not change a routine that has been working well for you.
  3.  Over and Under-hydrating: This can be a bit daunting after what was discussed above, but the key is to listen to your body. One tip I have is when hydrating for a race, try and be consistent. You can start 3-5 days prior, but the key is taking small sips. One awesome tip I learned was to set a timer for every 15 minutes. When the timer goes off, take one swig of water. When at rest, your body can only absorb so much water before it just dilutes your blood serum levels and salt concentrations.
  4. Practice using your fuel source during several long runs leading up to the race. Don’t start a new gel/gu/waffle/drink the day of the race. It’s that simple! Feel free to experiment with a couple different brands to see how your body responds to them a few months before race day.
  5. Adapt to the weather: Did you know that in hot conditions, you should reduce your carbohydrate intake by about 10%? This is because your body’s oxidation rate is 10% lowered in hot environments. So focus more on consistent hydration. 


There is a lot of information to unpack in this blog, and this just begins to tap into that! This is something that we discuss with athletes who are in our run coaching program and in our marathon/half-marathon coaching programs! If these services are something you are interested in, email us at info@perfectstridept.com or call 917- 494- 4284


Written by:

Brian McLaughlin, PT, DPT, OCS, RRCA Run Coach, CFSC Strength Coach



Vitale K, Getzin A. Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients. 2019 Jun 7;11(6):1289. doi: 10.3390/nu11061289. PMID: 31181616; PMCID: PMC6628334.

Jäger R., Kerksick C.M., Campbell B.I., Cribb P.J., Wells S.D., Skwiat T.M., Purpura M., Ziegenfuss T.N., Ferrando A.A., Arent S.M., et al. International Society of Sports Nutrition Position Stand: Protein and Exercise. J. Int. Soc. Sports Nutr. 2017;14:20. doi: 10.1186/s12970-017-0177-8.

Burke L.M., Hawley J.A., Wong S.H.S., Jeukendrup A.E. Carbohydrates for Training and Competition. J. Sports Sci. 2011;29(Suppl. 1):S17–S27. doi: 10.1080/02640414.2011.585473. 

Wang Z, Qiu B, Gao J, Del Coso J. Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-Analysis. Nutrients. 2022 Dec 28;15(1):148. doi: 10.3390/nu15010148. PMID: 36615805; PMCID: PMC9824573.

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