An Ode to Carbs
SNACK girl is my freakin’ unicorn. Stomping around in desperate demand to be fed is a favorite past-time of mine and my internal hangry-toddler usually emerges full force when I’m training. I want all of my athletes to channel this energy too, pursuing giant chocolate chip cookies and pizza and breakfast burritos with as much gusto as they do running or biking. But…wait…all of the foods I just listed are…carbohydrates. Aren’t carbs bad for endurance athletes?
No. No. No. No. . . NO.
There’s so much nutrition information out there these days that is often misconstrued and oversimplified. One of the more prevalent ones that never seems to go away is the idea that carbs are bad. For endurance athletes, the notion that carbs are bad is often twisted into the idea that they will only be successful if they change to a high fat diet in order to become fat adapted. This last statement is oversimplified (explained more below). SNACK girl and I are here to tell you that when you’re training a f*ck ton, you should be eating a f*ck ton, and what your body needs is a f*ck ton of carbs.
Why does my body need carbs? If I’m an endurance athlete and I reduce my carb intake, won’t my body just turn to using fat instead?
There is often the idea in exercise that our body only burns one fuel at a time. In certain scenarios, this can be true. Max effort sprints will preferentially use carbohydrates. A Zone 1 multi-day backpack in the woods will preferentially burn fat. However, multiple factors affect the fuel source utilized during exercise. Exercise intensity, duration, the length of time you’ve been training and your fitness level, muscle fiber type, and the food we eat during will all play a role in the type of fuel we use.
When we eat carbohydrates, our body breaks them down into their individual building blocks for absorption so it can use them for energy. The main sugar building block of carbohydrates is glucose and it is our body’s primary preferred source of energy. That’s right. In a game of middle school dodgeball, glucose is that annoying kid in the front of the pack that always gets picked first. Once our body has used up glucose for all of its daily functional needs (i.e. living) it stores the remaining glucose it has as glycogen in our liver and in our muscle (so long as it gets enough from the diet). Our body can only store so much though, which is why we need to eat carbohydrates to keep the stock full.
The main sugar building block of carbohydrates is glucose and it is our body’s primary preferred source of energy.
In general, during sustained exercise at submaximal intensities (~65% of VO2Max) , glycogen is utilized as the preferential fuel source for energy along with some fat. However, if the bout of exercise continues past 2-4 hours and the athlete consumes little to no carbohydrate during the effort, our muscle and liver glycogen stores become depleted. Most of us have felt this at some point in training, the dreaded bonk.
While trained athletes can shift into utilizing fat for energy, it does not negate the body's need for carbs. In fact, our body's can actually (and will) break down stored protein in our muscle and transform it into glucose to meet its needs. This same scenario occurs with an athlete who is training every day and not eating enough carbohydrates in their daily diet to replenish their depleted glycogen. That’s right – the muscle you’ve been training and putting in hours of work to build and adapt is being broken down so the body can make glucose for its everyday needs. When you’re training or simply exercising consistently, your energy needs increase substantially. So in addition to eating carbohydrates to simply feed your body, you need extra to properly fuel your workouts and extra-extra on top of that to replenish your glycogen stores for the next workout. If you want to make gains in your training, you have to give your body the fuel it needs and it needs carbs.
A lot of sports nutrition is situational and there are a lot of different factors that play into substrate utilization, like the training type and status of the athlete. For example, an untrained or beginner athlete who is just getting into endurance exercise may quickly go into carbohydrate utilization during an easy hour run. Whereas an athlete whose training has consisted of 85-90% sub-max Zone 1 and Zone 2 workouts for, say, 3 years will easily use fat as a fuel source for a 2-4 hour event EVEN if – wait for it – they eat carbohydrates. The body can still burn fat during endurance exercise even if you consume ample amounts of carbohydrates both during and outside of exercise. Eating carbohydrates puts some money in the (glycogen) bank and helps to spare protein, allowing your muscles to recover and adapt to the training load. (Plus, as a fun perk, eating carbohydrates keeps your body, you know, alive and all that).
Carbohydrates are not bad.
Bottom Line: Being an endurance athlete does not negate your body’s need for carbs. Fuel use in the body is not singular and your body needs fuel sources from all macronutrients to function and recover properly. Adapting as an athlete depends on the culmination and combination of consistent training, the type of exercise you are doing, and your diet. There is a lot more situational variability to this subject; however, this blog post is simply meant to debunk some of the myths surrounding carbohydrates and give a general 101 into how your body utilizes them and why they are necessary in your diet as an endurance athlete.
Nutrition should be individualized just as much as our training is individualized. (If a coach gave an athlete completing their first ever 30k trail run the same training plan as a veteran ultra-runner completing their dozenth 100 mile, you’d question their sanity. The same mindset should apply to the food we put in our bodies). There is no one diet that works for all endurance athletes. There is no one macronutrient that works for all training modalities. And bottom line: Carbohydrates are not bad.
In addition to being one of your favorite coaches at TMP, Colleen is about to complete her Master’s in Dietetics and Nutrition from Montana State University.