Ahh, the pre-race pasta dinner. It's not just an opportunity to bond with fellow athletes, it's also the last remaining excuse to think of spaghetti as health food. Carb loading isn't necessary for everyone, but if you're one of the people who will benefit, it's time to learn the right way to do it.
Illustration by Tara Jacoby
Here's the theory: Spaghetti is made of carbohydrates and your muscles love carbohydrates. They love carbs so much they keep some around, in a form called glycogen, embedded in muscle tissue. Chowing down on pasta tops up the glycogen tank, putting you in the best possible shape for race day.
The unfortunate marathoner who doesn't top up her glycogen stores faces a terrible fate: hitting the wall. As you run, you burn calories from a mix of body fat, a little bit of body protein and glycogen. Run out of glycogen and you're suddenly missing a main fuel source. Your brain will tell your muscles to slow down and you'll be one of those people staggering down the street even if you felt great just a few miles before.
Who Needs to Carb Load?
Forget marathoners for a minute. What about the rest of us? Pasta parties are popular in team sports, but you don't need to carb load for a short race or an hour-long game: you easily have an hour's worth of glycogen in your muscles. The rule of thumb is to consider carb loading for races or efforts that will last more than 90 minutes at a moderate to hard effort. So marathoners, triathletes and anybody doing a multi-hour endurance sport should be thinking about their glycogen stores.
That means huge swaths of athletes are off the hook: basketball players, whose games are shorter than our cutoff. Baseball players, whose games might last a couple hours but involve a lot of sitting and standing around. Runners lining up for a 5k, where they will work fantastically hard but only for 20 or 30 minutes. This doesn't mean you shouldn't have a pasta party, just that the purpose is team bonding. If you don't have a team, shrug and say "This is my race week ritual." Nobody questions an athlete's rituals.
One more caveat: carb loading is only necessary if you can't eat during the race. Remember that we're just sating our muscles' craving for carbs. You can put carbs straight into your bloodstream by eating them. This is what gels are for, those packets of syrupy stuff that, while they may be gross, are easy to swallow on the run. Same idea behind sport jelly beans (yes, those are a real thing), energy blocks or chews, energy bars and so on. Ultrarunner Dean Karnazes famously ordered and ate a whole pizza while running a 199-mile race. (The secret, he says, is to request it unsliced, then roll it up like a burrito.)
Since most of us can't choke down pizzas while working out, carb loading is still valuable. We can only absorb about 60 grams of carbs per hour under the best circumstances. Less may leave you under-fuelled (especially if you didn't start eating until late in the race), and more isn't helping and could make you feel sick. Try out different foods while training — yes, you have to practice eating. Then, when race day comes, carb load as insurance.
How to Properly Carb Load
You twirl the pasta around the fork and then — wait, no. It's a little more complicated.
There are a few protocols that really maximise glycogen storage, and they work best if you're otherwise not exercising much. If you're already tapering to prepare for the race, they fit in perfectly. (The rule of thumb on tapering: one day per mile of your goal race. So a marathoner will gradually reduce their workouts over the 26 days before the race, or a half-marathoner for about two weeks.)
A carb binge the night before the race will add some glycogen to your muscles, and a few days of high-carb eating is probably better, but we can improve on that with a little physiological trickery. A fun fact about those glycogen stores: they're not a fixed size. It's possible to actually make them able to hold more.
The original carb loading protocol — which nobody does anymore — started a week before race day. You'd do a long workout meant to deplete your glycogen stores (so, running a marathon a week before your marathon) followed by a couple days on Atkins-diet levels of carbs: 10% of calories or less. (This is agonizing if you're not used to it.) The idea was to get your glycogen stores emptied out, so that the next time your body saw carbs it would grab them and kiss them and pack them in and want to hoard them and love them forever. In the three days leading up to your race, you'd eat 90% of calories from carbs, filling up those enlarged glycogen stores to their max.
There's a newer technique that achieves similar results without the pain and suffering: call it the Western Australia protocol. The day before the race — so Saturday morning if you have a Sunday marathon — you do a short but intense workout involving an all-out 30 second sprint. This will make your muscles hungry for carbs, and for the remaining 24 hours you oblige with pancakes and pasta. This is the easiest way to effectively carb load.
Listen to Your Own Body
While carb loading can provide insurance against hitting the wall, it's no guarantee — other factors can lead to fatigue, and fiddling with diet can't overcome problems that come from not training enough.
The practical side of carb loading involves knowing your body: can you eat while running? Can you binge on carbs for a day and not end up with diarrhoea? Do you even like spaghetti? If you choose to add carb loading to your race-week toolbox, make sure to test it out in training first. Since every gram of glycogen requires your body to store two grams of water, some runners would rather avoid maximizing their stores. It makes them feel bloated and stiff.
There's also some doubt about whether women benefit as much from carb loading as men. (Most of the research was, sigh, only done on guys). It seems like women can carb load, but need to up their calories to do it, which may mean taking in 30% more food than what they normally eat. Again, this is something to test out before race day.
Some athletes have luck going the opposite direction: instead of charging up their carbohydrate stores, they train their body to run more on fat than on carbs. (You'll always use both; they're just adjusting the proportions.) It may take three weeks to get used to exercising on a low-carb diet, but if you prefer bacon to spaghetti, this may be an approach worth trying. As long as — once again — you try it long before your race day.