Why Runners Need Carbs


You’ve laced up your running shoes, fired up your tunes and are ready to nail your run. But did you remember to get your carbs in? Yes, they get a lot of flack in certain circles, but carbohydrates can be the most important nutrient on tough training days. Here’s the low-down on how your body fuels up and uses carbohydrates for energy.


Carbohydrates, specifically glucose, keep you going during a run. Glucose is converted into energy that contracts exercising muscles — the faster and longer you run the more glucose you use. Key things to know about glucose:

  • Glucose is needed for you to optimally burn fat during your run. During long runs, fat is the other important nutrient that turns to fuel, but your body can’t properly use fat without glucose present.
  • Glucose is the number one fuel for your brain almost all of the time. The brain detects when glucose levels in the blood drop, and you experience it as confusion, disorientation and fatigue — hello, bonking! Having enough glucose on board can prevent you from hitting the dreaded “wall.”
  • You have a limitless capacity to store fat, but not glucose. Your body stores glucose in the liver and in your muscles in the form of glycogen. And your body can only store enough glycogen for about 90 minutes of strenuous exercise — which explains why many runners choose to “carb load” before a race.


Eating high-carb foods leading up to a race — or “carb loading” — stocks your muscles and liver with glycogen. But it’s only necessary if you’re exercising intensely and continuously for 90 minutes or longer. (If you did it before every run, you’d likely notice your shorts getting snug.) To get the most bang from your carb-loading buck:

  • 1–3 days before a long run, ramp up your carbohydrate intake with a high-carbohydrate diet. Average runners should aim for 5–7 grams of carbohydrates per kilogram of body weight, and endurance athletes should aim for up to 10 grams of carbohydrates per kilogram of body weight.
  • 3 to 4 hours before exercising, eat a high-carbohydrate, low-fat meal, such as a turkey sandwich with lettuce and tomato, or pasta with chicken and veggies.
  • Right before the race, opt for simple carbs that are easy to digest — like white rice, pasta, pancakes, cereal, fruit bars and baked goods — to avoid stomach trouble on the road.


Taking in carbs during a run slows down the rate at which you use your stored glycogen, and helps keep you going for longer — which explains why you’ll find sports drinks and gels at aid stations for long races. When you consume carbs and protein post-exercise, you set your body up to optimally restock glycogen stores for the next run and help rebuild muscles. A few things to keep in mind when fueling on the run and after:

  • 30 minutes before exercising, have a simple carbohydrate snack, like a piece of fruit, applesauce, a handful of dried fruit or crackers.
  • During physical exertion, aim to sip 8 ounces of sports drinks every 30 minutes, or consume  1–2 sports gel packets with water every 45–60 minutes.
  • Within 30–60 minutes after exercising, have a snack or meal that combines carbohydrates and protein. Some good options: a peanut butter sandwich, chocolate milk, a banana with a serving of almonds.

Be sure to connect MapMyRun and MyFitnessPal so can you can easily track your fuel alongside the calories you burn running.


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