Carbs (not calories) during exercise
Carbohydrate intake during endurance exercise delays fatigue and improves performance. This has been known since the 1920’s. For most of us, it doesn’t have to be complicated. Unlike with fluid intake, there is no current research to suggest taking in a certain percentage of the carbs you’re burning, or a certain percentage of your body mass (during exercise). And no need to count total calories: intake of protein and fat is not necessary during exercise (but some athletes like a bit). The American College of Sports Medicine recommends 30-60 grams of carbs per hour for exercise lasting longer than 90 minutes (that’s about 1-2 energy gels per hour). Of course, there are still lots of questions you could ask. Here are a few.
I have never tried / I don’t like taking in carbs during a run. Will I still benefit from less than 30 grams per hour?
Yes. A recent study found a performance increase (1%) for endurance athletes taking in just 9 grams per hour! That’s about 150mL of sports drink. The study found larger improvements with larger amounts, but the point is that all is not lost if you can’t get up to 30 grams per hour. There are still benefits to be had!
I’m a 10k runner. Can carb intake still help my performance?
Yes. And it’s all in your head. In a shorter race, your on-board energy supply won’t run out, so your body may not need the extra carbs. But your brain still takes notice.Recent studies have shown that areas of the brain associated with performance get an extra boost when carbohydrate is taken into the mouth (before it is swallowed), resulting in improved performance. There are receptors inside your mouth that communicate directly with the brain. So all you have to do is drink, rinse (for about 3-5 seconds), and spit! The effect is still present if you use a tasteless carb source, but isnot seen if you use artificial sweetener. Even for long-distance runners, this “mouth rinse” protocol is an idea if you’re having trouble actually getting carbs down.
I’m a big guy. Do I need to take in more carbs than a smaller athlete?
No and Yes. The limiting factor for how much carbohydrate you can take in is how quickly the carbs can get out of your stomach and into your bloodstream. And there’s no evidence to say that a larger person can clear carbs from their stomach better than a smaller person. So your body mass does not dictate how much carbohydrate you are able take in. However, a bigger athlete does stand to benefit less than a smaller athlete from the same amount of carbs, so it’s still in your best interest to shoot for the higher intake ranges. Side note: If you’re small, recognize that there is a lot of potential for carbohydrate intake to help your performance! Your body gets more “bang for your buck” than a larger person!
I’m chasing a marathon PB and looking for an edge. Will more than 60 grams per hour give me any more of a performance benefit?
Yes, as long as your stomach can handle it. According to the same study that found a small benefit from 9 grams per hour, the performance benefits increase as the amount of carbohydrate increases, up to about 80 grams per hour. Performance improved by almost 5% at this level. But before you go and slam back 3 gels an hour in your next marathon, you need to seek out products with multiple types of carbs, and you need to train your gut:
#1 Find carb sources containing both glucose and fructose. There are different paths for getting carbs into your blood: one for glucose, and one for fructose. By taking in both types, you’re able to take advantage of both paths and increase intake beyond the “traditional” 60 gram per hour limit. Most sports nutrition products contain multiple types of carbs, and pretty much all the other names of carbs you’ll see (sucrose, maltodextrin, dextrose, brown rice syrup) boil down to either glucose or fructose or both. But each form does have differences in flavour and sweetness to suit different tastes.
#2 Train your gut! If you’re used to 1 gel per hour, it would be unwise to immediately go for 3 on race day. But just like your muscles, your gut is trainable. So build up your tolerance to more carbs in the same way you build up your tolerance to longer runs during training. But like with any training, it may not be possible for you to achieve the highest intake levels. Yet another thing you may have to leave to the pros.
Update: Here is a 2018 article from Alex Hutchinson talking about a recent study on gut training during exercise. The gist of it is - you will likely run into some stomach issues when trying to train your gut to take in more carbohydrate, but don't let that discourage you - your body can get better at taking in carbs if you continue to practice!
I have never tried / I don’t like taking in carbs during a run. Will I still benefit from less than 30 grams per hour?
Yes. A recent study found a performance increase (1%) for endurance athletes taking in just 9 grams per hour! That’s about 150mL of sports drink. The study found larger improvements with larger amounts, but the point is that all is not lost if you can’t get up to 30 grams per hour. There are still benefits to be had!
I’m a 10k runner. Can carb intake still help my performance?
Yes. And it’s all in your head. In a shorter race, your on-board energy supply won’t run out, so your body may not need the extra carbs. But your brain still takes notice.Recent studies have shown that areas of the brain associated with performance get an extra boost when carbohydrate is taken into the mouth (before it is swallowed), resulting in improved performance. There are receptors inside your mouth that communicate directly with the brain. So all you have to do is drink, rinse (for about 3-5 seconds), and spit! The effect is still present if you use a tasteless carb source, but isnot seen if you use artificial sweetener. Even for long-distance runners, this “mouth rinse” protocol is an idea if you’re having trouble actually getting carbs down.
I’m a big guy. Do I need to take in more carbs than a smaller athlete?
No and Yes. The limiting factor for how much carbohydrate you can take in is how quickly the carbs can get out of your stomach and into your bloodstream. And there’s no evidence to say that a larger person can clear carbs from their stomach better than a smaller person. So your body mass does not dictate how much carbohydrate you are able take in. However, a bigger athlete does stand to benefit less than a smaller athlete from the same amount of carbs, so it’s still in your best interest to shoot for the higher intake ranges. Side note: If you’re small, recognize that there is a lot of potential for carbohydrate intake to help your performance! Your body gets more “bang for your buck” than a larger person!
I’m chasing a marathon PB and looking for an edge. Will more than 60 grams per hour give me any more of a performance benefit?
Yes, as long as your stomach can handle it. According to the same study that found a small benefit from 9 grams per hour, the performance benefits increase as the amount of carbohydrate increases, up to about 80 grams per hour. Performance improved by almost 5% at this level. But before you go and slam back 3 gels an hour in your next marathon, you need to seek out products with multiple types of carbs, and you need to train your gut:
#1 Find carb sources containing both glucose and fructose. There are different paths for getting carbs into your blood: one for glucose, and one for fructose. By taking in both types, you’re able to take advantage of both paths and increase intake beyond the “traditional” 60 gram per hour limit. Most sports nutrition products contain multiple types of carbs, and pretty much all the other names of carbs you’ll see (sucrose, maltodextrin, dextrose, brown rice syrup) boil down to either glucose or fructose or both. But each form does have differences in flavour and sweetness to suit different tastes.
#2 Train your gut! If you’re used to 1 gel per hour, it would be unwise to immediately go for 3 on race day. But just like your muscles, your gut is trainable. So build up your tolerance to more carbs in the same way you build up your tolerance to longer runs during training. But like with any training, it may not be possible for you to achieve the highest intake levels. Yet another thing you may have to leave to the pros.
Update: Here is a 2018 article from Alex Hutchinson talking about a recent study on gut training during exercise. The gist of it is - you will likely run into some stomach issues when trying to train your gut to take in more carbohydrate, but don't let that discourage you - your body can get better at taking in carbs if you continue to practice!
