How Many Calories Should I Consume Per Hour?

By Shawn Dolan PhD, RD, CSSD

The primary reason to consume calories during endurance exercise is to provide carbohydrate to the working muscle and brain. This becomes increasingly important as the duration of training/competition lasts longer than 60-90 minutes due to the body’s limited capacity to store carbohydrate (glycogen). The ability to digest and utilize carbohydrate is dependent on the amount and types of carbohydrate consumed. Individual carbohydrate sources have different transport mechanisms in the gastrointestinal tract which allow for different rates of absorption. There is good physiological data to support an upper limit in our ability to breakdown carbohydrate during exercise. However, the upper limit is increased if there are multiple sources of carbohydrate consumed. By selecting a product with more than one source (e.g. sucrose and fructose), you are able to absorb more than when you consume a single source (e.g. glucose only).

The general recommendation is to consume 30 – 60 grams of carbohydrate per hour or 120 – 240 calories per hour during endurance exercise. Although at face value the recommendation appears straightforward, there are several influential factors each athlete should consider. Furthermore, the discussion should include both the science and the specific application in order for each athlete to develop an individual fueling plan and put it into practice.

Take a look at the following athlete scenarios and identify the differences.

Joe is an Ironman distance triathlete who typically finishes a race in 10 – 11 hours. He consumes 300 – 360 calories per hour (75 – 90 grams of carbohydrate) during the bike portion of the event, 200 – 250 calories per hour (50 – 60 grams of carbohydrate) during the run portion of the event. He consumes EFS Sports Drink and EFS Liquid Shot to obtain carbohydrate (calories). These products provide multiple sources of carbohydrate.

Then consider Brent – an ultrarunner who typically finishes a 100 mile race in 24 – 26 hours. He consumes 100 – 175 calories per hour (25 – 45 grams of carbohydrate). He relies on EFS Liquid Shot (with water) and snacks provided on the course. Again, multiple sources of carbohydrate are included in the shot.

Why does Joe consume more calories on the bike than the run? Why does Joe consume more calories than Brent when running, even though it is the same mode of exercise?

Consider the following factors that might alter the number of calories (carbohydrate) consumed.

Intensity of Exercise:  When the intensity of exercise is high (beyond lactate threshold), more carbohydrate is used as a fuel source, possibly requiring more to be consumed (depending on duration).

Duration of Exercise: When the duration of moderate to high intensity exercise lasts longer than 2 – 3 hours, more carbohydrate is recommended (up to 90 grams per hour) as long as multiple sources are consumed; however, if the duration is significantly longer (> 10 hours),  lower recommendations typically apply (especially when a single mode of exercise is performed).

Mode of Exercise: Athletes are typically able to consume larger amounts of carbohydrate during cycling than running due to the different nature of the exercise.

Fitness Level and Training Method: Athletes who have a higher level of fitness and train their aerobic metabolism have a greater ability to use fat as a fuel source during exercise and therefore rely less on carbohydrate.

Number of Carbohydrate Sources in Product:  If a training session lasts longer than 2 – 3 hours, select a product with multiple carbohydrate sources. If the training session is less than 2 – 3 hours, one source (e.g. glucose) may be adequate.

Source of Carbohydrate:  Some carbohydrate sources are more readily absorbed than others; glucose, sucrose, and maltodextrin are absorbed more quickly than fructose, galactose, and amylose.

Heat and Humidity:  In a hot and/or humid environment the body requires a greater amount of carbohydrate; however, the GI system is often less able to digest and absorb carbohydrate, requiring a fine balance between supplying enough but not too much.

Altitude:  At higher altitudes there is an increase in utilization of carbohydrate as a fuel source, which may require larger amounts to be consumed.

As you plan for your next race, consider the factors listed above to determine the best number of calories for YOU to consume per hour. Take a look at your sport nutrition product label to identify the carbohydrate sources and amount per serving to help you individualize your nutrition plan.  Taking the extra time to analyze your carbohydrate intake and modifying it to optimize your performance just may pay off.

11 replies
  1. Doug Baumgarten
    Doug Baumgarten says:

    Thanks for a good review. But most athletes USE 600-900 calories per hour during intense training or racing. So how can ingesting 120-240 per hour be sufficient for longer-distance events, particularly in athletes who have almost no body fat? While some loss of weight due to negative caloric balance is expected, why not consume more calories – closer to the number expended? I have an athlete training for Race Across America (RAAM), an epic bike “race” lasting 10-12 days. I can’t see 120-240 calories per hour being sufficient, as he expects to ride up to 20 hours per day….

  2. Rich
    Rich says:

    I am training for my first Ironman in November. I am going to be fifty at the time of the event and weigh 170 Ibs. I was wondering if it’s possible to use all EFS products during the event? I have trouble using GU products and powerbars. Also, I’m figuring that I will need to take in 300-350 calories/hr. for the bike portion and 200-250 calories/hr. for the run. Does that make sense and again is it possible with EFS sports drink and shots? Thanks so much.


  3. John
    John says:

    Doug –
    Just coming from a user of FE products, this isn’t an all encompassing article. Different extreme events require much different caloric needs. You can’t live off of FE products for a 10 day, 200 hour race and they will tell you that. Those super length races very much depend on many different sources of fuel including “real food”
    The second part is recovery is very important to the whole equation. You don’t need to take in unnecessary calories during your workout or race. Your post race recovery drink and meal are extremely important as is sleep.

    Rich –
    I use nearly all the FE products, Optygen, Multi-V, EFS, Ultragen, and the bars and gels too. Look at their product usage guide under Research, to see how they recommend using their various products for different race lengths and how it’s safe to use all the products for all aspects of your training and racing.

    I enjoy all their products!

  4. Shawn
    Shawn says:

    Thank you for your comments. Please keep in mind, the general recommendations are a baseline to start calculating individual needs. Each athlete should experiment with different amounts during specific training phases. During certain types of competition, additional calories may be required and/or tolerated. It is very difficult for the GI to absorb significantly higher amounts of calories, particularly during very high intensity training. When competing is such a long duration race, the pre-race and recovery meals will be critical as well.

  5. Shawn
    Shawn says:

    Hi Rich,
    Your calorie calculations look appropriate for your Ironman race. The amount could vary depending on your goal finish time. You can certainly rely on FE products to fuel your race. I would recommend a high quality pre-race meal to start the day. During the race use the during drink, gel, and possibly bars. Be sure to outline your nutrition plan and practice using the products during your key long training sessions.

    John…thank for your input as well!


  6. H. Armstrong
    H. Armstrong says:

    Just looking at simple math, during a bike race I burn 900-1000 calories an hour. You’d find me in a ditch on the side of the road/trail if I ingested 300-400 calories an hour, especially if we are talking about marathon races and races such as Leadville. Ask yourself this: When is the last time you saw an *overnourished* elite athlete?????????

  7. Robert Kunz MS
    Robert Kunz MS says:

    H. Armstrong,
    You are correct in stating that you burn 900-1000 calories per hour. Understand that most of those calories are being supplied by your stored fat. Even the leanest endurance athletes have days worth of calories stored as fat. At efforts below threshold your body burns mostly fat, not carbohydrates. As your effort increases your start to burn proportionately more carbohydrates than fat. The purpose of fueling for short and long events is to keep your glycogen/carbohydrate levels as high as possible since its this energy system that determines how well you will perform in your racing. Most athletes only have an ability to absorb 120-400 calories per hour, which certainly can be enough for any distance racing. The goal being to replace as much carbohydrates as you burn.
    Of course at the end of the day your total caloric deficit does need to be replaced with your post exercise meals. At this point your body will convert those calories back into the glycogen and fat you have depleted.

  8. H. Armstrong
    H. Armstrong says:

    Thanks for responding. I have a few thoughts:

    Several comments:
    1) The article mentions “Athletes who have a higher level of fitness and train their aerobic metabolism have a greater ability to use fat as a fuel source during exercise…” Has body fat been measured before and after exercise in long duration exercise? So many athletes (especially those who would use FE products) have very little body fat to utilize in the first place. And not just any body fat can be used for this fuel. Someone with 4% body fat has nothing more to give as that 4% is essential for survival and protection of visceral organs.
    2) When glucose drops below ~54, the brain starts to suffer. Do we really know how often an endurance athlete is actually hypoglycemic. It’s probably often in my observation.
    3) In the hypoglycemic state the brain will utilize lactic acid and ketones as a fuel source.
    4) I think a fair question to ask athletes is: Do you really want your brain fed or not and what are you willing to do for that? Are you willing to give yourself more food during exercise (within reasonable limits) or carry just a bit more fat.
    5) Are there any studies measuring blood glucose levels during an endurance event while an athlete is consuming the number of calories suggested in this article. I think therein lies the real answer to the conundrum.

    ~Heidi Armstrong

  9. patti rosen
    patti rosen says:

    Interesting comments.
    If you look at what your heart monitor shows you, and I noticed this this weekend, when I do a workout at 90% the computer says my use of carbs is very high and my use of fat is fairly low. ON a race like I did this weekend which was only 2 hours, I can afford to start to with a hypoglycemic load (EFS bar) before the race and to use just EFS drink on the bike and sips of EFS shots a half hour in and an hour in while on the bike. During the run I can use just ultragen for fuel and fluids and electrolytes and get plenty of calories and feel strong. Because the shot is a fairly concentrated carb source if you want to increase your carb load for longer runs it can be done easily.

    I would do the same technique on an ironman except depending on heat I might add a salt supplement to avoid hyponatremia. I would also say be prepared to some extent before by teaching your body to use the fuel you need in a long race by training above threshold, in the heat and in the hills.

  10. Robert Kunz MS
    Robert Kunz MS says:

    Heidi Armstrong,
    You ask some great questions which can be researched in a number of different ways. One reputable method is to test RER which gives an accurate measure of an athletes fat burning vs glycogen burning at a given effort. With this calculation you can determine how much glycogen you are burning at a given power output and can then determine an effective energy replacement schedule.
    Also understand that its been widely documented that even athletes with 4% body fat have the available fat stores to go for days, so for the leanest athletes it is still not necessary to consume any fat.
    You are correct in that exercising often in a hypoglycemic state is not healthy and not something that is recommended. However the body is very adaptable and within reason exercising from time to time with lower carbohydrate consumption can improve your bodies ability to utilize fat as fuel source more effectively. Balance is key.


Trackbacks & Pingbacks

  1. […] How many calories should I consume per hour from First Endurance […]

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *