Let me start this conversation by saying that nutrition and fueling is highly personal and individualized. (Go back and read those italics again. ;) ) There is no one magical strategy that will work exactly correctly for everyone, but after this many years of coaching literally hundreds of individual athletes, I do believe it’s possible for each person to dial in on a strategy that works well for them. This article is intended to give you a starting point from which you can hone in on a plan that works well for you.
Determining your sweat rate is an important first step in this process, because it gives you a very solid starting range for fluid consumption per hour during exercise. The second step is determining how much fuel you should consume per hour.
Carbohydrates have been given a bad rap in popular culture over the last several decades, but let me emphasize this: Workouts are not the time to steer away from carbohydrates.
Carbohydrates are the body’s preferred energy source during exercise. Yes, there have been many fads over the years that try to steer away from this truth, but the basic physiology is this: the body works best during exercise when carbohydrates are the fuel source. Using carbohydrates for energy helps preserve your muscle tissue by preventing your body from using protein as an energy source. In short, consuming carbohydrates helps prevent your body from eating its own muscles as an energy source.
Consuming fuel (and more specifically, fuel that contains carbohydrates) during exercise keeps your blood sugar concentrations topped off. Metaphorically speaking, you are “stoking your fire” rather than letting it burn out. Most athletes have experienced hitting the proverbial wall, and fueling is what helps us avoid this.
You can consume foods that contain fat and protein during exercise, but you do not want the dominant sources of calories to be coming from these macronutrients due to the fact that it is harder for the body to metabolize fats and proteins during workouts. During exercise, blood flow is diverted away from the gastrointestinal (GI) tract and to the working muscles, so this limits and slows down in-workout metabolism.
Hydration is a critical part of the fueling conversation because the stomach needs a certain osmolality to trigger gastric emptying, which is the transfer of liquids and fuel from your stomach to the small intestine and the other parts of the GI tract. (Osmolality is a fancy word that refers to the ratio/balance of carbohydrates and other nutrients to liquids in the body.) Osmolality also impacts how nutrients are absorbed through the walls of the intestines and into the blood. Without proper hydration, your body will not properly metabolize your fuel (this applies during workouts as well as in your daily life).
As of the time of this writing (in late summer 2022), there are literally thousands of sports nutrition products on the market that make fueling “easy.” I put quotes on “easy” because the sheer amount of sports nutrition products can make this feel very overwhelming. Here are just some examples of sports nutrition products:
As an athlete, I personally have benefitted from using sports nutrition products (I’ve actually personally tried and/or used all of the products I listed above). They are easy to use in terms of packaging and portability and the nutrition information is easy to find (so I can map out my nutrition plan well). In the context of a “normal” busy life, those things have made it easy for me to make a fueling plan, stick to it, and therefore get the fuel I need (which helps me get the performances I want). For these reasons, I often recommend that athletes start with sports nutrition products when they are first formulating a fueling and hydration plan.
However, sports nutrition products may not be right for everyone. Whether it’s a personal preference, a budget concern, or a dietary restriction (personal choice or a limiter for health reasons), some athletes choose to forge their own path and make their own foods. Resources such as Feed Zone Portables or Rocket Fuel can help assist with this.
When determining how much fuel you should consume per hour of exercise, there are a few important things to keep in mind:
The body cannot metabolize more than 60 grams of carbohydrates per hour if the carbohydrate source is glucose alone.
The body can metabolize up to 90 grams of carbohydrates per hour if the carbohdyrate source is a blend of simple sugars, such as glucose, dextrose, sucrose, and fructose.
These numbers include all sources of carbohydrates, whether they are liquid or solid.
Again, everyone is different, so you’ll need to dial in on what works best for you. Very generally speaking, if you have a higher body weight, you will require more fuel. Your fueling needs will be slightly lower if your sport is a jostling one (such as running) versus if it is a non-jostling one (such as cycling). (Basically, if you are bouncing around a lot, your guts are also bouncing around, which slows down metabolism while you are exercising. This means that the total amount of fuel you can consume is limited in jostling sports.)
A good starting target range to aim for is 60 grams of carbohydrates per hour. You can tweak it based on your notes and feedback from your workouts to hone in on exactly what target range is optimal for you and your sport of choice.
In lieu of grams of carbohydrates per hour, calories per hour can also be used as a target (and this is best done for athletes who are consuming real foods or sports nutrition products that have calories coming from more macronutrient sources than just carbohydrates). Again, your range is specific to you, but a good starting target range is 200-300 calories per hour. In general, you should be replenishing at least 25-35% of the calories you are burning per hour (no matter what type of activity you are doing). This range will help keep you going strong and prevent you from hitting the wall.
However, remember that you are not combiningthe grams per hour and calories per hour target totals. Choose one or the other and stick to that. Then, consume that amount each hour that you are exercising. This isn't meant to be an "average per hour;" you literally need to be consuming a specific and set amount of fuel each and every hour that you're exercising so you can keep those blood glucose levels stable and keep your energy levels where they need to be to sustain the workout or race you are doing.
Now that you have a starting point for how much you should be consuming per hour, you should plan to break that number up into smaller intervals.
I strongly recommend using duration-based nutrition and hydration plans. Duration-based plans allow for you to ensure that you are getting in the proper amount of liquids and nutrients each hour. You may hear of people doing this based on miles, but that can get dicey since the amount of time each mile (or group of miles) takes is not always the same. Duration is a more consistent way to control your fueling plan, no matter what sport you’re doing, what conditions you’re in, or what terrain you’re on.
Generally speaking, breaking each hour up into quarters works well for a lot of people. So, for instance, you would be fueling or hydrating (or a combination of the two) every fifteen minutes throughout an hour, and therefore every fifteen minutes throughout your workout or race. To accomplish this, you would divide the total number of liquid ounces you want to consume for hydration by four; you would do the same thing for the total number of calories or grams of carbohydrates per hour that you want to consume. Then, every fifteen minutes, you consume a quarter of the amount of each thing (fuel and hydration) that you want to consume over the course of the hour.
You can ultimately opt for whatever time intervals you like (such as every ten or twenty minutes), but the point here is that you want to have small enough intervals that you can take in a sufficient amount of fuel without overwhelming your GI tract and have them be regularly timed so you can keep that metabolism fire stoked. Whatever you do, you don’t want to be consuming all of your fuel and hydration for a single hour in a single serving. That’s asking for trouble to come knocking at your back door. (Pun intended.)
Mapping It Out
Now that we’ve gone over some of the basic elements of fueling, it’s time to map out your fueling and hydration plan. I highly recommend that you plan this out in advance by writing it down. (Yes, with an actual pen and paper.) To assist you with this, I’ve created a handy Fueling & Hydration Plan Worksheet that you can download and use.
Since reading a plan while you’re out on your workout or in your race is impractical, you’ll ultimately want to formulate a plan that is easy for you to memorize (which snowballs into making it easier to execute). For this reason, I’ve found that fueling and hydration plans are best executed when they are relatively simple.
By “simple,” I mean that sticking to the same hydration sources (such as one sports drink and water) and limiting your solid fueling options (such as sticking to just Picky Bars or just chews) can streamline this process. Fueling during a workout and/or race is serving a purpose; you are doing a job. This is not the time to seek out a full smorgasbord of options and flavors; save that for after your workout or race.
May The Fuel Be With You
You can read about fueling and hydration all day long, but the only way you’ll learn what works for you (and - sometimes more importantly - what doesn’t work for you) is by making a plan and trying it out. Map out your fueling and hydration plan, give it a go, take good notes about how it went, and then tweak it moving forward. Once you dial-in on a plan that works for you, I recommend that you stick to it. (If it ain’t broke, don’t fix it!)
Now, go forth, and May The Fuel Be With You!
Disclosure: Some of the links above are affiliate links, meaning, at no additional cost to you, I will earn a commission if you click through and make a purchase. Thank you for your support!
Coach Laura Henry
Laura Henry is a Syracuse, NY-based coach who is a USA Triathlon Level II Long Course and Level II Paratriathlon Certified Coach, USA Cycling Level 2 Certified Coach, VFS Certified Bike Fitter, and has successfully completed NASM's Certified Personal Trainer course. Coach Laura is passionate about helping athletes of all ability levels reach their goals and has coached many athletes to success.