Carbo Loading for Runners

Carbo-Loading for the Marathon


You’ve probably heard that you need to “carbo-load” before long races like a half-marathon, marathon or ultramarathon. Here’s my take on carbo-loading, including what I ate before winning the US National Masters Trail Marathon Championship.

Carbo-Loading Origins

Carbo-loading came into vogue after exercise science perfected the muscle biopsy. I’ve had one done and while it’s not that invasive, it does involve the physiologist inserting a large needle into your muscle and pulling out a core sample. The sample of muscle tissue is then “stained” with different chemicals so the physiologist can determine lots of cool things like your percentage of fast twitch to slow twitch muscle fibers, glycogen levels, capillary beds, etc.

Muscle biopsies in exercise physiology corresponded with the first running boom in the early 1970s. Physiologists began testing runners to see what was happening when they were successful and when they were not. From the muscle biopsies of runners who “hit the wall,” muscle glycogen (the stored carbohydrate in our muscles) was low, thus began the quest to see how to increase the muscle glycogen stores to help runners avoid the “wall.”

Early Carbo-Loading Techniques

Coaches (who always seem to figure out what works before physiologists do) had already seen that using long distance runs could help runners avoid the wall and that increasing carbohydrates in the diet was helpful as well. There is even a story of Arthur Lydiard telling his Olympic runners to add another spoonful (or two) of honey to their morning coffee before heading out for their 22-mile long runs because they would perform better. And of course, Lydiard championed the idea that doing regular long runs could help runners of all distances delay fatigue.

Deplete, Deprive, Replenish Method

Taking it a step further, researchers wanted to see if they could really maximize muscle glycogen stores right before a long race by first depleting them and then refilling them.  It was known that when muscle glycogen stores are low, there is a really strong stimulus in the body to refill them. (You can read more about this in my Runner’s Ultimate Nutritional Recovery Routine article.)

From this research, the first carbo-loading regimen – deplete, deprive, replenish – was created. It is a logical and simple strategy, but does have some serious drawbacks.

In this strategy, you begin seven days before your race. You first do a big workout to fully deplete your glycogen stores. This is usually a speed workout with lots of repetitions to burn through your carbohydrate stores. But it could be any running that depletes your glycogen stores. Then, and this was the critical step in this method, you avoided carbohydrates over the next three days. That’s right. You purposely ate a low carbohydrate diet so as not to refill your glycogen stores.

Then, three days before your race, you began to eat lots of carbohydrates. Your body, having been deprived, would quickly and maximally restock your glycogen stores and you’d then have a “full tank” of glycogen for the race.

Sure enough, it worked! Research showed that if you followed this regimen, you would indeed have really full glycogen stores.

However, this big glycogen tank came at a cost. First, you had to do a really hard workout just seven days before your big race. This introduced a risk of injury, peaking too soon and was generally worrying for the athlete.

Second, by depriving the runner of carbohydrates for the three days after the glycogen-depleting workout, she would feel very, very bad in the next few runs. No energy. Very tired and often quite grumpy. The legs were dead and heavy and the runner often felt very, very unfit. As you might imagine, this is not the ideal mental state for someone with a big race coming up.  I have known runners who tried this original carbo-loading technique and from my perspective, it just wasn’t worth it given the mental beating the runners took.

The Modified Method

Due to the negative issues with the original carbo-loading method, researchers evaluated a modified version that would skip the depletion/deprivation phase and just focus on the loading phase. Luckily for all of us, it worked!

Just like with the deplete-deprive-replenish method, the modified method resulted in a big increase in muscle glycogen. Technically, the depletion method may have resulted in slightly more glycogen storage but the differences were minimal and certainly the ability to avoid the negative physical and mental issues with the depletion-deprecation-repletion method was well worth it!

As a result, the Modified Method has become the go-to method for carbo-loading. You eat your normal diet in the first few days of race week and then simply increase the proportion of calories coming from carbohydrates in the last three days. Because you avoid the depletion and deprivation phase, you feel better in your runs/workouts the last week of your taper and you also avoid the mental issues – grumpiness, loss of confidence due to poor workouts, etc. It’s just a much more manageable strategy.

If you search the internet, you’ll find some really detailed formulae on how much carbohydrate to eat based on your age, gender, etc. but to be honest I find that simply making sure you have a good carbohydrate component in each meal works just fine and is less complicated.

What this means is that in each meal in the last three days before your race, you make sure you include carbohydrates. It doesn’t have to be complicated but you simply make sure each meal is rich in carbohydrates.  I’ve included what I ate at each meal in the three days leading into my championship race at the bottom of the this article and you’ll see that it wasn’t complicated.


Though the modified carbo-loading method is very simple, there are a few caveats to be aware of.

First, note that this is not overeating. You aren’t “stuffing yourself” to get fuller glycogen stores. You are simply adjusting each meal to have a larger carbohydrate component. Overeating (which is common due to nervousness) is not what you want.

Second, for every gram of stored glycogen there are four grams of water stored along with it.  As a result, you may see a slight increase in body weight so don’t worry if you are a pound or two heavier for race morning. That weight is extra glycogen and water and both will help you in the race.

Third, reduce your fiber intake in the last three days. This is the opposite of what you do normally. Normally, you are trying to eat more fiber in your diet but since fiber can be tough on the GI system, in carbo-loading, you reduce fiber intake. That means that instead of whole wheat toast (high fiber) you would select white bread toast (low fiber). I know it sounds crazy but for these three days you want to give your GI system a break and reduce the fiber intake. This is especially true for those that have had GI issues during races.

Lastly, practice your carbo-loading plan on a few long runs. This will help you dial it in just like you dial in your race nutrition by practicing it during some of your workouts. As is always the case, don’t try anything radical. Just eat things you normally eat with the exception of choosing lower fiber options. Then, once you know what works best for you, pre-plan your meals the last three days (especially for when you arrive at the race site) so you can relax and not stress about what to eat.

Final Thoughts

Because it’s so easy to carbo-load using the modified method, I highly recommend every runner carbo-load before long races. Note that the proper method is NOT just to eat a huge carbohydrate meal the night before the race (i.e., the traditional “pasta dinner”). It is a multi-day method and when done correctly not only results in full glycogen stores – but also boosts your confidence as you are never hungry, feel good on runs and know what will work with your GI system.  I’ve seen too many runners wait till the last day, then gorge at the pasta dinner then wake up race morning with an upset stomach.

To summarize: I’m a fan of adjusting the proportion of calories coming from carbohydrates in the last three days before your race but caution runners to not go overboard. You don’t eat more. Let me say this again, you don’t eat more calories but you simply include a bit more carbohydrates in your meals than you might otherwise. Remember, your training volume has reduced in your taper before the race so your stores are already less compromised than usual and I’ve found just a slight increase in carbohydrate intake works well (i.e., you don’t need to pig out on the carbo dinner the night before; just be reasonable.). Most importantly, eat what has worked for you in training and you’ll be fine.

(You might also like my article on Carbohydrate Periodization for how to use or not use carbohydrates during training.)

My carbo-loading strategy before winning the US Masters Trail Marathon Championships


Breakfast: Scrambled eggs, grits with butter, banana, black tea with cream and sugar

Lunch: Rice, roasted chicken, steamed broccoli, water

Dinner: Salmon, rice, sautéed kale, white wine

Notes: In between meals, I also drank water with electrolytes. I prefer mineral/sparkling water but will occasionally simply add electrolytes (like Generation UCAN Hydrate) to plain water. This was done each day leading into the race and I avoided over hydration but made sure I was never thirsty and was urinating every two hours and it was straw-colored. Dark color urine = dehydrated. Clear urine = over hydrated.


Breakfast: Scrambled eggs, grits with butter, banana, black tea with cream and sugar

Lunch: Rice, roasted chicken, steamed broccoli, water

Dinner: Chicken and pasta, red sauce, red wine

Notes: A creature of habit, I tend to eat the same breakfast and lunch during carbo-loading. I flew to the race site on Thursday afternoon so the dinner was at the hotel.

Friday (Day before the race)

Breakfast: Oatmeal, boiled eggs, banana, black tea with cream and sugar

Lunch: Pizza (veggie), lemonade

Dinner: Cheeseburger, fries, lemonade

Notes: All of these meals were at the race site. Breakfast was in the hotel (it was complementary) and lunch and dinner were at local restaurants that I had scouted before leaving home.

Now, I know what you’re saying, “You ate pizza and a cheeseburger the day before your race?!”  Here is the deal. I wasn’t eating fast food. I found local restaurants that were highly rated and offered healthier options for those meals. And secondly, I have found a healthy pizza to work very, very well for my stomach. I have it as my lunch (and feel it’s really my last opportunity to get in a lot of carbohydrates as I like to eat a “comfort” food meal for dinner) before races and have been doing it since high school.  So, it’s tried and true for me.

Lastly, I have two go-to dinners for the night before a marathon. I either have salmon and rice or if there is a good cheeseburger place, I eat a burger and fries. On this occasion, there was a local pub that was known for their cheeseburgers, so I ate there. From years of training and racing, I have found that I do better when I focus on the carbo-loading in the days before (modified method) and then have some comfort food so I sleep better the night before a marathon.  I’m not saying this will work for everyone and that’s why I suggest you experiment in training and figure out what works for you.

Saturday (Race Day)

Breakfast: Egg sandwich, black tea with cream and sugar, shake

Result: Master National Champion – Trail Marathon

As always, let me know if I can be of any help.


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