Should Cyclist Fuel With 100+ Grams Of Carbohydrate Per Hour?

There’s been much press recently about the extreme carbohydrate intake that many professional cyclists have been reported to achieve on the bike. With talk of intakes as high as 140 grams of carbohydrates an hour, supposedly the new normal within the pro peloton and sports nutrition brands now even recommending it to the masses...

Science In Sport Beta Fuel 
Mathieu Van Der Poels Race Nutrition Plan 
GCN, Do More Carbs = Better Performance 

These extremely high carbohydrate intakes stem from research showing that we can use as much as 105 grams of carbohydrates per hour from sports drinks consumed during exercise when using a mix of glucose and fructose. However, this is not a recent scientific breakthrough; a study as far back as 2005 (https://pubmed.ncbi.nlm.nih.gov/15946410/) showed this.

Does this mean you, as an athlete, should be aiming for such high carbohydrate intakes, and more importantly does it even improve performance? Here are seven reasons why you shouldn’t and it probably won’t…

1.⁠ ⁠Oxidative Efficiency—At high carbohydrate intakes (i.e.,> 80 grams an hour), not all of the carbohydrates consumed are used by the muscle. 

For example, the highest amount of ingested carbohydrates ever recorded to be used by the working muscles during exercise was 108g/hr; however, to achieve this, more than 120g/hr of carbohydrates had to be consumed. 

The theory is that the excess is likely not being digested within the gut. This then means that over a period of a few hours, which is generally the only time that you’d recommend using high intakes of carbohydrates, you are accumulating undigested carbohydrates within the gut. Over a few hours of riding, this could translate into quite a large volume of undigested carbohydrates sat sloshing around your gut. 

Our ability to oxidise (i.e. burn) carbohydrates from things like sports drinks appears to be individual to us. There is some suggestion we maybe able to train this through a high carbohydrate diet. If we take the below figure from a recent study (https://pubmed.ncbi.nlm.nih.gov/35446596/) where participants were fed 120 grams of carbohydrates an hour, you can see how variable it is, with some athletes able to oxidise as little as 72 grams an hour and some as much as 108 grams per hour. 

We generally see the highest oxidative efficiency with intakes of carbohydrates around 90 grams an hour. Where generally, a very large proportion of the fuel ingested is utilised by the muscle, with little left accumulating in the gut. 

2.⁠ ⁠Stomach Issues — If you have a debilitating stitch or are jumping off the bike for the nearest port aloo, you’re not going to perform to your full potential in a race. High carbohydrate intake during exercise stresses the digestive system, particularly when you consider that based on point 1, ingesting very high intakes of carbohydrates is likely to lead to a backing up of carbs in the gut. 

Any stomach issues experienced from super high intakes of carbohydrates will likely negate any performance benefit of the extra ingested carbohydrate in the first place. 
Unless you have a highly trained digestive system and are well accustomed to high intakes of carbohydrates, it's likely going too high with your carbohydrate intake will cause you issues. 

3.⁠ ⁠Accelerated Glycogen Use — It’s been shown that carbohydrate intakes above 90 g/hr can actually increase the rate of muscle glycogen use and suppress fat oxidation, so you can end up using up your own precious glycogen stores quicker; this is not likely to be beneficial for performance and if anything is likely to result in premature fatigue. 

4.⁠ ⁠Performance — More carbohydrates don’t necessarily equal better performance. We have almost no data from well-controlled studies to show us that taking in high intakes of carbohydrates actually leads to better performance. In fact, the few studies we have (Here's one of the best out there - https://pubmed.ncbi.nlm.nih.gov/22968309/) that compare the effect of different doses on performance suggest intakes in the region of 80 grams may be better for performance compared to doses as high as 120 grams an hour. This could be related to a lot of different factors such as the exercise task, the individual's tolerance and their feeding regime. 

5.⁠ ⁠You’re Not A Pro — As an amateur rider, or certainly a rider not racing in the pro peloton and unable to sustain the insane power outputs that those riders can. You won’t be expending as much energy as one, so don’t try to fuel like one. 

The exercise intensity is a key driver of fuelling demands, and riders able to push our insane power outputs may see performance benefits to these high intakes, particuarly towards the end of exercise as stored glycogen becomes depleted. 

Always think twice before trying to replicate what pro cyclists are supposedly doing (many of them may not been doing what’s reported in the media). For best performance, go for a dose of carbohydrate that you can tolerate well. 

6. Total Daily Carbohydrate — Generally, our goal over the course of the day is to eat enough to meet our daily needs. If you’re smashing in 120 grams an hour, you’re eating a huge amount of your daily energy needs on the bike. To stay in energy balance, you’re then likely to compromise your fuelling pre and post-session which may negatively impact on your glycogen stores pre exercise and your recovery post exercise. Given that glycogen is really important for performance, and starting glycogen is likely more important than fuelling on the bike, too much fuel on the bike may not be a wise strategy. 

7. Logistics – Quite simply, unless you have the ability to be fed by a team car, or stack fuel on the route you’re riding, trying to carry sufficient fuel on the bike to achieve such high intakes is logistically a challenge. Also add in the challenges with simply eating that much whilst riding a technical trail or holding a position in the bunch and you can see some of the issues with doing this.

As with many things in sports nutrition, context really matters, and whilst this is an exciting and new strategy, it may not always be appropriate for you as an individual.

- Coach Ben