Why Carbs are Essential to a Performance Diet

Nutrition
By Susan Kitchen
Despite some fad diet rules, carbohydrates are an important part of a high-performance diet

Athletes are just as susceptible to dieting trends as everyone else. Runners looking to transform into faster, leaner running machines might cut carbs or eliminate fat to get an edge. Other times, runners might omit dairy and grains from their plates in an effort to eat like human ancestors from thousands of years ago.

Fad diets are nothing new. From Atkins to Paleo, to Whole 30 and Keto (short for Ketogenic), many diets either eliminate a whole food group or have a starring villain. In some diets, carbohydrates are the bad guy. Carbs, namely sugar, are labeled the villain and come with a nasty reputation.

You’ve likely heard the rumors that carbs are unhealthy, cause weight gain, reduce the body's ability to burn fat or contribute to diabetes. But the truth is that carbs—the human body's favorite fuel source—are an essential part of an athlete's diet.

Let’s take the popular Ketogenic diet, a low-carb, high-fat diet that drastically reduces carb intake to <50g per day. It was originally developed to help reduce seizures in children with uncontrolled epilepsy but has since gained mainstream popularity.

Eliminating or drastically reducing an essential macronutrient, like carbs, should immediately raise red flags (unless you have a specific health condition). Here’s why.

The Role of Carbs in an Athlete's Diet

Carbohydrates are essential for health and serve as the primary fuel for the body. Before you even lace up your running shoes, your body requires about 120 grams of carbs (about 500 calories) per day to fuel the brain, support the central nervous system, and maintain red-blood cell production and immune health.

During exercise, your body uses carbs for energy in the form of glucose. This fuel assists in fat metabolism, delays fatigue and promotes recovery. In high-intensity exercise, carbs are responsible for converting fat to glucose quickly—it’s like burning fat in a carbohydrate-fueled flame.

The proverbial “wall” or “bonking” referred to by runners occurs when glycogen (long-chain glucose in the muscle) stores are depleted. In the absence of glycogen, no fuel is available to quickly convert fat into usable fuel.

The body’s glycogen stores in muscles and liver are limited, though. Fully stocked, we are fueled for approximately a two-hour effort at moderate intensity. But the higher the effort, the more carbs you use and the faster you burn through glycogen stores. That’s where eating comes in.

What you eat day to day and the timing relative to exercise directly impacts how much glycogen you have in the tank. Adequate carbohydrate intake that matches activity level can safeguard your glycogen storage, muscle tissue, support blood sugar levels during exercise, optimize recovery and protect your immune system.

Carbs are an important part of a runner's diet

Daily Carb Recommendations for Athletes

Some of the healthiest and fastest runners in the world consume a carbohydrate-rich diet. “Eating carbs is almost a universal practice among the world’s best endurance athletes,” says Matt Fitzgerald, a dietitian, writer and endurance runner. Fitzgerald explains the typical Kenyan diet is 78 percent carbs, and they dominate in distance running.

Still, the research and rumors on carbohydrates may, at a glance, conflict. However, you can experience great performance without sabotaging your health or body composition goals by prioritizing wholesome, nutrient-dense carb sources in place of processed, refined or nutrient-poor choices.

There are two types of carbohydrates: simple and complex. Both types of carbs break down into glucose (sugar), which fuels your body, but the difference is in how long that process takes.

Complex carbohydrates, like sweet potatoes, brown or wild rice, and oatmeal, are slow to break down and provide vitamins, minerals and fiber. These are the types of carbs you should eat before running. Simple sugars, like bananas, honey and table sugar, break down quickly. Reach for simple sugars to top off your energy before a run or bolster it during a lengthy race or workout.

Be choosy with your carb choices, and plan carb consumption around exercise sessions and the most active parts of the day. For example, a morning runner should include carbs at breakfast and lunch but can taper off carbs at dinner and include more veggies and fruit. (Exception: If it’s the night before a long, intense workout or race, don’t skimp on carbs at dinner.)

The amount of carbs you need depends on your weight, training volume and workout intensity.

A simple way to manage appropriate carb intake based on training load is by the portion size on your plate.

  • Off-season or lighter training days: 25 percent of your plate should be carbs
  • Intense peak-training days, race phase: Carbs should make up 50 percent of your plate

Once you start moving, though, you might need to take in more carbs. To maintain blood glucose levels and keep glycogen stores from hitting empty during your workouts, supplementing with sports nutrition products is wise during long or intense training sessions.

  • Low intensity, 45-75 minutes: No fueling is required*
  • Moderate to high intensity, up to 75 minutes: Hydrate and fuel if needed
  • Endurance/intermittent high-intensity, up to 2.5 hours: 30-60 g/hr
  • Endurance/ultra-endurance, more than 2.5 hours: 60-90 g/hr

*Water is recommended. Electrolytes may be necessary for extreme sweating. “Low intensity” includes activities such as golf, yoga and walking the dog around the neighborhood

A woman sets her Garmin Forerunner 645 Music watch

Prioritize Carbs for Recovery

Post-workout recovery fuel is designed to speed up the repairing of damaged muscle tissue, replace glycogen/energy stores and promote physical adaptation. Immediately following a training session, muscle cells are open, insulin sensitivity is elevated and the body is primed to absorb simple sugar and protein. The faster you refill the tank, the faster the body gets the green light to lean up and burn body fat.

The optimal recovery window to jump-start the process is within 30 minutes after a workout.

Insulin sensitivity declines and muscles take longer to absorb glucose from the bloodstream as time goes by, making glycogen storage less than optimal. What’s worse, failure to replenish lost glycogen can mess up your hormones, which creates a stressful environment for your body. Your body in turn releases cortisol, a stress hormone that promotes fat storage, especially around your midsection.

By consuming a recovery snack within 30 minutes, you can extend your ability to effectively refill glycogen stores. You can maintain that ability for up to eight hours by snacking on carbs every couple of hours.

If you skip a recovery snack, your glycogen stores fall to <50% about two to two and a half hours after a workout. This lack of glycogen stores doesn’t bode well for recovery or for the tidal wave of cravings that will hit you later.

Refueling is not essential, though, after an easy recovery workout or an after-dinner stroll. Consuming regular, well-balanced meals will suffice on easy or rest days. The recovery fuel is intended for intense, extended or tough workouts or when you are feeling depleted and wrung out.

How Many Carbs to Eat After a Workout

Athletes should eat a snack or small meal that contains carbs and protein within 30 to 45 minutes after a workout. Men should follow a 3:1 ratio of carbs to protein, while women need a tighter 2:1 ratio immediately following workouts to jumpstart anabolic triggers that repair and aid muscle growth.

It’s important to include both carbs and protein because they work in tandem to boost glycogen storage, reduce inflammation and boost immunity. Research shows that athletes who consume a recovery snack with the right carb-to-protein ratio can restock glycogen stores four times faster than those who refuel with carbs alone.

The amount of food you eat, though, depends on the length and intensity of your workout. Here are some general guidelines:

  • Workouts lasting less than one hour: Eat 20-30g protein and 40-60g carbs
  • Moderate workouts of 1-3 hours: Get 20-30g protein and 60-90g carbs
  • Long endurance workouts of 3-10 hours: Consume 25-30g protein and 60-90g carbswithin 30-45 minutes of finishing. Add another 0-30g protein and 60-90g carbs within two hours of your workout. Grab about 20-30g protein and 60-90g carbs at the four-hour mark.

It’s common to have a decreased appetite following a hard workout. If you're not into eating solid food right after exercise, choose a cold liquid that sounds refreshing and goes down easy.

Blend up a mango smoothie with a scoop of whey protein and either fat-free yogurt or sweetened almond milk. Or pour a glass of low-fat chocolate milk and eat a handful of almonds or Greek yogurt for added protein.

But don't worry about counting each gram of carbs and protein—consuming specific amounts of each nutrient is not nearly as important as just making sure you eat something within 30 minutes of finishing. Find something you like with roughly more carbs than protein—a peanut butter and jelly sandwich is a great option—and you'll be on your way to a healthy recovery.

Here are some common ingredients you can use to refuel:

  • Cow's milk: 12g carbs, 8g protein per 8oz
  • Fairlife milk: 12g carbs, 12-13g protein per 8oz
  • Whey protein: 20g protein per 1 scoop
  • Almonds: 6-7g protein per 1 oz (about 20 almonds)
  • Peanut butter: 8g protein per two tablespoons
  • Greek Yogurt: 15-20g protein per 5-8 oz, depending on brand
  • Sweetened almond milk: 14g carbs, 1g protein (unsweetened 1-2g carbs)

Knowledge is empowering. You can get closer to achieving your goals by understanding carbohydrates’ role in supporting your body, health and active lifestyle.


By Susan Kitchen. Susan is a Sports Certified Registered Dietitian, USA Triathlon Level II Endurance Coach, IRONMAN Certified Coach, published author and founder of Race Smart, a sports nutrition and coaching company.