Does Your Size Determine Your Carbohydrate Intake During Endurance Sports?



A common question among athletes is whether a larger athlete should eat more carbohydrates hourly during training than their smaller counterpart?

It may seem counter intuitive that carbohydrate requirements could be the same for athletes of different sizes. Most would assume that if you are bigger with more muscle, you would need more carbohydrates during training.

Unlike daily nutrition, where we determine macro-nutrient needs based on an athlete’s weight, training intensity and duration, when it comes to training nutrition, carbohydrate intake is determined based on absorption rates of carbohydrates through the intestines. Basically, most adults have similar sized intestines, therefor their stature will not be the determining factor in their nutrition during training.

I’ve worked with 120lb athletes who consumed 80-90g/hour during 3-5 hour races and also worked with  180 pound  athletes who consumed 60-70g/hour during 3-5 hour races. Both had done trial and error and found their sweet spot and the carbohydrate needs that worked for them.

Single and Multiple Carbohydrate Sources:

Oxidation rates of single carbohydrates; for example glucose; consumed alone, max out at about 60g/hour.

Oxidation rates of multiple transportable carbohydrates; ex.glucose + fructose, glucose + maltodextrin; max out closer to approximately 100g/hour. There are some recent studies looking at additional intakes which haven’t seemed to improve performance. Higher intakes could also lead to GI (gastrointestinal) distress.

The majority of sports nutrition products have been produced using multiple carbohydrate sources: gels, chews, quality sports drinks. As a practical example, the average gel has 30g of carbohydrates and the average sports drink has anywhere from 20g-30g of carbohydrates. Alternatively a whole food such as a medium banana has approximately 25g of carbohydrates.


How Many Carbohydrates Do You Need?

The recommended range of intake falls between 30-100g of carbohydrates hourly. The duration and intensity of your workout, as well as your fitness level, will all factor into what works best for you.

For moderate to intense “training sessions” over 90 minutes in duration, consuming carbohydrates does delay the onset of glycogen depletion and improve performance. Research has shown significant improvements in time to completion during 40km time trial performances by doing a repeated mouth rinse with a carbohydrate sports drink, which means carbohydrates can even improve performance in high intensity efforts as short as one hour. This is related to the brain and carbohydrate receptors in the mouth, not glycogen stores. The mechanism is not completely understood, however it appears the brain gets the message that sugar is coming and the muscles respond positively.  This gives you good reason to start that 60-90 minute criterium or time trial with a few mouthfuls of sports drink or a gel and a water bottle on hand.

You can completely deplete your glycogen stores in 90 minutes of hard training. That would be even shorter if you went into an event with fairly low stores to begin with and if the event is very high intensity.

Focus On What Works For You, Not Your Training Partner:

Find a fueling strategy that works for you during training and execute it during competition for optimal performance. Practice what you will try on race day during training. Race day is never the time to experiment. You can train your gut to absorb carbohydrates better with practice.  It’s not only your legs and arms that can respond to training, your gut does as well.

Start a journal with your hourly carbohydrate intake during different types of training rides, along with how you felt by the end of your session. Assuming all other things were in place (daily nutrition included the proper macronutrient intakes and hydration), work from here. If you were fading during the session or as it was ending, up your hourly intake for the next session. If you were strong until the end, did you need as much as you consumed? By paying attention, you will find what works for you for each particular type of workout.

Keep in mind, the more intense your training is, the higher the oxidation rate of carbohydrates. One hour of high intensity training will use more carbohydrates than the same time training at moderate intensity. Not all workouts will be equal in their fuel requirements.

Remember, don’t look to your left and right on a training ride to determine what your carbohydrate intakes should be, because that lightweight rider beside you may actually need more carbohydrates than you do for a majority of reasons. Focus on yourself and your own nutritional needs.


NSAG – Next Level Performance Nutrition