Your body uses three things for fuel: carbohydrates, fats and proteins. Let’s focus on carbs. Everyone knows you need to “carbo load” for endurance sports, right? But, why? And how? And when?

What are Carbohydrates?

For our purposes, carbohydrates include any type of sugar. They’re comprised of a few or many building blocks called saccharides. Your body converts saccharides to glucose, which fuels all activities—including exercise.

Kinds of Carbs

Simple sugars include the glucose in table sugar, the fructose in fruits, and the lactose in dairy products. Additionally, processed foods, white bread, pasta and white rice fall into this category. They’re “simple” because they’re comprised of just one or two saccharides. As such, they’re easily digested and provide a quick energy source.

Complex carbohydrates are what we stereotypically consider “carbs”. They’re long strands of saccharides found in foods like whole grains, quinoa and starchy vegetables like potatoes, beans and lentils. While it takes longer to digest complex carbs, they provide a much higher concentration and more sustainable source of fuel.

Carbs are stored as glycogen in the liver. When your body depletes readily available sugars during intense and prolonged exercise, it releases glycogen for fuel. Low levels of glycogen cause fatigue and reduced athletic performance.

Carbo Loading

Before Exercise

You should certainly ensure your tank is full prior to exercise. Aim to consume 6-10 g/kg of carbohydrates daily to maintain adequate glycogen reserves. That’s 409-681 g for a 150 lb athlete.

During Exercise

During physical activity longer than one hour, take in simple, easily digested carbohydrates to restore adequate blood levels of fuel. 30-60 grams suffices, which can be found in most sports drinks and gels, but don’t forget fruit and grains as more natural alternatives.

After Exercise

While preloading with carbs has gained the most publicity, it’s actually the 30-minute to 2-hour window after exercise that optimizes carbohydrate intake. This is when your body most efficiently converts carbohydrates into glycogen and enhances recovery. Adding protein to your post-workout snack not only facilitates muscle repair, but it also augments glycogen production. Aim to take in 50-70 grams of carbs and add protein at a 3:1 or 4:1 ratio for the maximal benefit. Chocolate milk, Greek yogurt with berries and a banana, protein shakes or bars, or commercially available recovery drinks are all excellent choices.

The Skinny on Low Carb Diets

Limiting carbohydrates in your diet, particularly as a weight loss strategy, is not recommended for athletes. Without an adequate fuel source, your body will break down muscle instead and increase your risk of injury and illness, prolong your recovery, and impair your performance.

The Bottom Line

Particularly during heavy training builds with intense workouts, no recovery day, or multiple workouts in one day restoring liver glycogen stores becomes of upmost importance. So carb up to keep up!