Marathon week carb loading: simplified
I originally wrote this post during Boston Marathon week last year, but am reposting because it’s about that time again! The Wednesday or Thursday before a weekend marathon are when I typically have my runner clients start their carb load, so this is the perfect time to review all things carb loading.
Carb loading may boost performance
It’s true that carb loading can improve performance in endurance events 90 minutes or longer, by about 2-3%. That’s because carb loading, if done correctly, can increase the amount of stored carbohydrate (or glycogen) in your muscles and to a lesser extent, your liver. What this means is it will take longer for your muscles to use glycogen stores and become fatigued.
When to start carb loading
Ideally, a carb loading “plan” should start 6-7 days before your marathon. I am not a fan of “depletion” phases in carb loading, in the sense that you are pairing intense exercise/runs with a low carb diet before “loading.” It’s stressful on the body and not necessary. However, I do recommend eating a “normal” amount of carbs (~60% of your daily energy/calories) until you’re about 3 days out from the race. Then, you’ll want to start focusing on carbs more and make about 75% of your energy intake carbs. That’s about 3.5-5.5 grams of carb per pound of body weight, which is a lot, and also where I tend to see things go awry in runners.
More carbs, not more food
Ok, this is really important! Carbs should be a larger component to your diet in those 2-3 days before your marathon, but the amount of food you eat doesn’t necessarily have to change. That means protein, veggies and fat can take a backseat in order to fit in the carbs that you need. Focusing on hunger and fullness cues is still important here, so you’re eating when you feel hungry but also stopping when you’re comfortable, not stuffed. What that could look like in a 130 lb runner, who will need ~550 grams of carbs is:
Pre- taper run: banana, sports drink
Post-run: fruit smoothie
Breakfast: 1 cup fruit juice, plain bagel with peanut butter and jam, 2-3 dates
Snack: 2 servings pretzels
Lunch: Turkey sandwich on whole wheat or sourdough, 1 serving pita chips, orange, sports drink
Snack: 1 slice toast with banana and honey, one fruit flavored yogurt
Dinner: 2 cups pasta with tomato sauce, 2 slices of crusty bread
Snack: 2 chocolate chip cookies
Some bloating and weight gain is normal
When your muscles store glycogen, they store it with water. This is why you may feel a bit bloated and puffy, and your weight may be up a few pounds, in the days leading up to the marathon or any time during the taper. As uncomfortable as it is, it also means you are doing carb loading and tapering correctly! The key is to notice the difference between feeling overly full, in which case you may be eating too much in quantity, and feeling a little bloated overall. The discomfort will become a distant memory as you begin your 26.2 mile journey, I promise.
Race day eve and morning
Back to race day eve, in which I recommend sticking with a plan like the above. The key is to spread your carb intake evenly throughout the day, as opposed to trying to fit it all in during your dinner the night before the race. In the morning, you should have a plan for a steady intake of carbohydrates starting 3-4 hours before the race (see this post for more on race morning fueling).
Nothing new!
It should go without saying, but the days leading up to your marathon are not for trying new foods or recipes. You know your body, and your gut, by now and whether or not you need to cut down on high fiber foods like beans, vegetables, fruits and whole grains to avoid race day GI distress.
Happy running, friends. I’ll be cheering somewhere around mile 25-ish!
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