CARB LOADING SIMPLIFIED
If you have bonked on a run, hit a wall, felt broken after, or aren’t seeing the results you want then this post is for you.
My first ever marathon, I ate pasta the night before and brought one sleeve of fuel and thought it was enough for 26.2 miles. If it isn’t obvious, I hit a wall after the first couple of hours and felt so sore the days after the race. Back in 2016, I was new to running endurance distances and despite my pharmacy degree, I did not put in the energy to understand why carb loading matters and how to do it.
One of the biggest points I make as a running coach for my half marathon and marathon athletes is the importance of fueling before, during and after long runs. Let’s summarize the key points on why you should carb load, when to do it, and some suggestions on how to achieve a proper carb load.
WHY SHOULD I CARB LOAD?
Carbohydrates are stored in muscles and liver as glycogen, which is the primary fuel source during moderate-to-high intensity endurance exercise. Research shows that carb-loading can increase your glycogen stores, improve endurance performance, and delay fatigue in events longer than 90 minutes. If you maximize your glycogen stores before an endurance event, then you can prevent severe fatigue aka “hitting the wall.” By delaying your fatigue, then you can maintain a higher potential pace. The higher carb stores can also provide a nice buffer if you run into issues tolerating taking fuel during the event.
HOW SHOULD I CARB LOAD?
First you have to decide if a 1-2 days carb load (half marathon) or 2-3 day carb load (marathon) works for you. Personally, I prefer the longer duration because it’s easier to integrate the lower end of the recommended carbohydrate quantity over more days.
You will want to calculate your carb target, which you can use my calculator here.
1 kg body weight = 2.2 lbs
Carbohydrates to be consumed (g) = Body weight (kg) x carb target (g/kg)
For half marathon athletes, carb target is typically 7-10 g/kg/day
For marathon athletes, carb target is typically 8-12 g/kg/day
Example: For a 150 lb athlete, racing a marathon 600-900 g carbs/day. This is a big range and I recommend if you aren’t used to eating this quantity of carbs to start on the lower end of the range.
Common Mistakes:
Eating huge dinners instead of spreading carbs throughout the day
Too much fiber, which can cause GI distress (reduce fiber the day before the marathon)
Trying new foods
Not hydrating (drink fluids due to glycogen binding water)
Example Carb Load ~700 g carbs
Breakfast: Pancakes or waffles with syrup, banana or berries, orange or apple juice
Snack: Smoothie + granola bar
Lunch: Turkey sandwich on white bread, chips, serving of fruit
Snack: dried mango or dried apricots + energy bar
Dinner: 2 servings of white rice or large pasta serving, lean protein (fish or chicken), dinner roll or garlic bread (or my personal favorite is half a pizza)
Snack: Pretzels or cereal w/ milk
Sports drinks, sour candy, fig bars, dried fruit, juices are all easy ways to add in more carbs if needed
HOW SHOULD I APPROACH RACE DAY?
Race morning you want to work backwards from the start time of your event. A lot of races are super early with 7 AM start times and so if it doesn’t make sense for you to wake up at 3 AM to eat, then you want to top off glycogen stores as best as you can that morning and rely more on the days prior. In general, 1-4 g carbs/kg body weight 2-4 hours before the race is what you want to aim for. I don’t expect you to pull out your TI-89 and do math but if you think about simple, easy to digest carbs such as bagel and a banana, oatmeal with honey, toast with jam and a sports drink then you should be able to get in adequate carbs.
During your race, it is important to fuel from the beginning since you will burn through those glycogen stores you have worked so hard to build up. It is also better to front load the carbs when it is easier to digest them versus the second half of the race where digestion can become harder. I will never forget a seasoned friend telling me early on that if you start to feel hungry while you are running that you are in trouble because you are already behind on fueling. A solid minimum is 30-60 g carbs/hr but data supports 60 g carbs/hr for exercise that is 2-3 hours (if tolerated) and upwards of 90 g carbs/hr for ultra endurance events (PMID 24791914). So how many gels is that?
Most fuel on the market has 19-25 g carbs per serving and some high carb options contain 30-40 g carbs. You will want to practice your fueling on training runs to train your GI similar to training your lungs and legs. I suggest athletes take their fuel every 20-30 minutes or every 3-5 miles based on their ability to tolerate carb sources.
Chase the dream. Chase the joy. Remember fuel is your friend.
Ives
