“Carbo loading” (or carbohydrate loading) is a concept that many have heard of, but few understand – and it can make or break your sports performance. As a sports dietitian I am often asked a litany of questions about carbs and the truth is they are not all created equally, especially when it comes to fueling workouts. Here’s what you need to know about carbohydrate loading and how you can use it to optimize your performance.

What is carbo loading?

Many assume a bowl of pasta the night before a game or a bagel the morning of a race counts as carbohydrate loading (CL). While not entirely wrong, there’s much more to this concept. The goal of CL is to increase muscle stores of glycogen – the stored form of energy in muscle and liver cells. Long-duration exercise tends to rely heavily on glycogen for fuel and stores can easily run dry, leading to sharp crashes in energy levels. CL allows your muscles to stock up on extra fuel and allow for more sustained energy during those longer duration exercise events (think 90 minutes or more).

But carbo loading properly requires much more than just eating more carbs. You also need a corresponding decrease in activity, which helps to ensure that the energy from those carbs is stored for later instead of being used immediately.

Overall, if you can get carbo loading right, it can be overwhelmingly positive (who wouldn’t want more energy?). But it can be difficult to achieve, and there may be unpleasant gastrointestinal side effects. The steep spike in carb intake can cause bloating, gas and stomach discomfort. Extra water is stored in the cells along with glycogen, leading to some extra water weight gain during a course of CL.

How many carbs should you eat when carbo loading?

A common recommendation leading up to an endurance event, like a marathon, may approach 8 to 10 grams of carbs per kilogram body weight. That comes out to 545 to 680 grams per day for a 150-pound person. This would be a fairly substantial increase from the 6 grams per kilogram, or 410 grams commonly recommended for endurance exercise.

How do you carbo load properly?

If carbohydrate loading seems worthwhile, use these strategies to create the right protocol for you. If you are a competitive athlete, you can seek guidance from a registered dietitian who specializes in sports.

• Get a Head Start: Instead of just eating a large high-carb meal the night before, increase intake of carbs for three to five days leading up to an event. This will give you time to maximize glycogen stores and manage any potential side effects.
• Choose Carbs Wisely: Choose carbohydrate foods you like and know you tolerate well. Foods too high in fiber can increase unpleasant digestive side effects, so lower-fiber options are the way to go, especially before exercise.
• Expect Some Weight Gain: Some water weight shifts are to be expected, so plan for how this might make you feel during activity. And don’t worry, they will subside.
• Practice During Training: Carbo loading should be tested out during training, not in the days leading up to a race or other event. For best results try it out in the training days before long runs or other endurance type training to help simulate a competition day environment.
• Don’t Skip the Team Dinner: While a pregame meal or pasta dinner the night before doesn’t really count as carbo loading, getting in a meal with plenty of of carbs will never hurt performance.

Bottom Line: Adding carbo loading to your training can help increase glycogen levels and help better fuel performance. For best results, increase carbs, while also dialing back on exercise to allow muscles to stock up on glycogen and test out your tolerance ahead of competition and other athletic events.

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