How to Use Carb Loading to Prepare for Your Toughest Fitness Challenges

Perhaps the best part about preparing for an endurance event is carb-loadingthe borderline gluttonous consumption of pasta, bread, and all things starchy in the days leading up to competition. The goal is to top off the bodys fuel tank, and the crazy thing is that its not some made-up excuse to feast on all of the foods demonized by todays anti-carb culture. Science shows that carb-loading can help to boost your performanceif you do it right.

To understand why carb-loading works, you need to understand how the body actually utilizes carbohydrates, one of the three macronutrients that make up every food we eat. Many people think that eating carbs simply pads their waistline, but that only happens if you consume them in excess. Your bodys first priority when it comes to carbs is to store them as glycogen in your muscles and liver. During intense activity (e.g., a race), your body taps that glycogen to create glucose, which your cells use to produce energy.

Carb-loading (or as scientists call it glycogen supercompensation ) is a way to make sure that your bodys primary fuel stores are filled to the absolute brim. Most people have enough glycogen to sustain them for 90 to 120 minutes of intense activity, but if you train regularly and vigorously (as youll likely do in the months leading up to a race), you cant be sure that youre at full glycogen capacityand you definitely want to be if youre going to be racing for longer than 90 minutes.

Your move: As a general rule, if your event lasts less than an hour (think: 5k or 10K), you dont need to carb load. Simply eating a healthy, balanced diet should supply you with more than enough glycogen to get you across the finish line. But if your event will last longer than about 90 minutes (think: half marathon or marathon), consider increasing your carb intake beginning with the first meal after your last intense training sessionfor most people, that will be about three days before the event. During those final few days of increasingly lighter training, you want at least 70 percent of your calories to come from carbs.

To be clear, that doesnt mean you should be loading up on high-sugar foods like donuts and ice cream. You want to be chowing down on high quality carbs, such as rice, pasta, bread, potatoes, and lower-fiber fruits like bananas. You should also limit high-fiber foods, like beans, vegetables, and certain fruits (such as apples), as too much fiber can cause stomach discomfort when carb-loading. Supercompensating your glycogen stores in this manner wont make you faster, but it can help you go harder for longer, which might very well result in a new PR.