Why You Need Carbohydrates For CrossFit

Written By Kimber Rozier

With the popularity of Paleo and Keto in the CrossFit community, it seems like everyone is steering clear of carbohydrates. Whispers of how they’ll make you fat or sluggish radiate around the gym during warm-up. Talk of specialized paleo meal plans or keto supplements continues during the post-workout meal. Even intermittent fasters have skin in the game, as they often train on an empty stomach and don’t want to pack on those “dangerous” carbs without “earning it” first.

Clearly, there’s a reason for all of this hoopla. But how much of it is real, and how much of it is just very intelligent marketing? I hate to break it to you, but you might be surprised to learn that in order to excel in CrossFit, you need carbohydrates.

HOW MACRONUTRIENTS INTERACT WITH ENERGY METABOLISM

To start, let’s take an oversimplified, hopefully, less-boring adventure back to basic biology.

Your body has a few handy ways to produce energy. Its preferred method is taking glucose from the food you eat and breaking it down into ATP for energy through glycolysis. You can also break down fats to make energy directly in beta-oxidation, or use the degraded fat molecules to reproduce glucose through gluconeogenesis. Your body can break down protein into metabolites for either. Finally, you can use creatine phosphate for a quick burst, but we’ll get to that later.

Without spending too much time going into detail, the three main macronutrients can all form something called acetyl-CoA. In aerobic metabolism, this metabolite facilitates NADH and FADH reduction in the electron transport chain. This yields a ton of energy in its own right, but misses ATP production from the first few steps of glycolysis - substrate-level phosphorylation.

Hailing from glucose metabolism itself, your body can produce a few ATP molecules by creating pyruvate. This is basically step one of aerobic metabolism, before all of electron transport stuff, but it also serves as a critical generator in the absence of oxygen. During anaerobic metabolism, there are no oxygen molecules to receive electrons at the final step, so energy production is reliant on carbohydrates.

THE PHOSPHAGEN SYSTEM

OKAY, SO WHAT DOES THAT HAVE TO DO WITH METCONS?

As any savvy CrossFitter knows, metcon is short for metabolic conditioning. Your workouts are literally conditioning your metabolism to be more efficient in certain areas. That’s how you get fitter, stronger, leaner, and faster. It’s like improving any system - the better it can work as a whole, the more productive it is.

CrossFit uses every energy system that exists. Murph taxes your aerobic ability (and the will to endure) like no other. Fran or Isabel are pain-wrenching tests of anaerobic capacity. And squat 1RM test days rely on the phosphagen system. Just look at any Open or Games workout sequence and you’ll see what I mean.

Therefore, an athlete is only as good as their weakest link, your ability to perform relies on the conditioning of all of your energy systems. And without carbohydrates, you just can’t get there.

WHAT CARBOHYDRATES DO FOR CROSSFITTERS

First and foremost, carbohydrates are an energy source. A large majority of metcons test your anaerobic capacity, meaning you need glycogen or blood glucose to perform. Even aerobic-leaning metcons benefit from carbs, as fat oxidation takes forever, yields less overall energy than carbohydrates, and is heavily dependent on your respiratory quotient (RQ)

Your RQ is the ratio of CO2 produced to oxygen consumed. The harder you’re breathing during exercise, the more likely you’re experiencing an RQ closer to 1. Your respiratory rate increases in an effort to collect more oxygen from the air and expel carbon dioxide so you can keep training. The closer your RQ is to 1, the more reliant your cells are on carbohydrates for energy. Therefore, if you’re breathing heavily during a metcon, it’s safe to say your body wants carbohydrates.

CARBOHYDRATES HELP PRESERVE MUSCLE

CrossFit breaks you down. Period. You have to break down existing metabolites in order to produce energy. If there aren’t enough carbohydrates present around your workouts, there’s a chance your body will reach into your muscle.

Remember how we said protein can be broken down to make glucose for ATP production? That protein has to come from somewhere. As amino acids aren’t readily stored for future energy use, your body pulls from the best source it has - muscle tissue. Sure, it’s usually in cases of starvation that your body resorts to this extreme. But there’s definitely extensive scientific evidence that overtraining and improper nutrition can not only stunt muscle growth, but promote tissue breakdown.

CARBOHYDRATES HELP CONTROL CORTISOL

Carbohydrates directly reduce cortisol production. You may remember that cortisol is a stress hormone and is directly catabolic to muscle tissue. It also promotes fatigue when secreted, interferes with sleep, and is generally a negative for most recovery and adaptive processes. High carbohydrate consumption, especially after workouts, means lower cortisol levels and all-around better recovery. You’ll adapt better to training, which means more muscle over time.

CARBOHYDRATES HELP YOU RECOVER BETWEEN WORKOUTS

This applies to everyone who works out at high intensities. The nature of CrossFit requires you to push past your limits, which is what makes someone the fittest on earth. But even if you’re never going to be a Games competitor, most of us want to be able to walk the next day after DB step-overs and wall balls.

High-intensity exercise causes skeletal muscle damage, and carbohydrates can help limit that (see above). Damage to muscles reduces one’s ability to shuttle glucose into the muscle cell, which lowers the ability to replace glycogen stores, which makes for less recovery and more damage the next day. And so on and so forth in that cycle.

By feeding your body carbohydrates before, during, and after workouts, you mitigate breakdown, reduce soreness, and promote recovery. This is especially critical for anyone who trains or competes multiple times in one day, in both endurance and heavy resistance bouts. Get in quick-digesting carbohydrates as early and as often as you can around workouts, and gradually increase your general carbohydrate intake alongside training frequency.

WHEN IT'S OKAY TO RESTRICT CARBOHYDRATES

WHEN YOU SHOULD MAXIMIZE CARBOHYDRATE INTAKE

FINAL THOUGHTS

Training without carbohydrates is like trying to do a metcon in sandals - technically possible, probably not the best idea for optimal output. If you’re carb-restrictive, consider adding carbohydrates back into your pre-workout meals. You’ll probably feel better, and you might even shave a few seconds off of your best times. Remember - the harder you train at CrossFit, the more carbohydrates you need for fuel. And the more you can fuel your training, the better results you’ll get.