For someone who has spent the last year losing 35 pounds and being fairly careful with his diet, carbo loading is a scary thing to do. Carbohydrates are the enemy of most dieters. But to maximize performance in a marathon, you need to consume lots of carbohydrates, not just the day before the race, but for three days before the race. It's not possible to elevate your glycogen levels enough to make a difference in just one day. But eating a diet that is 75 to 90 percent carbohydrates can cause you to (hopefully) temporarily gain weight.
Most guides I've read suggest that carbo-loading will lead to temporary gains of two or three pounds. I've found my weight fluctuates more than that from day to day, so I wouldn't be surprised if I end up gaining five pounds or more. Gaining five pounds in three days after spending a year losing weight is the stuff nightmares are made of!
From what I've read, many runners fail to adequately carbo-load because they don't realize just how much carbohydrate consumption is necessary to elevate glycogen levels. During a distance run, your muscles can get energy from two sources: Glycogen stored in your body, and fat. Glycogen is the preferred option because it's much easier for your body to metabolize, but you have a limited supply. Even a very thin runner is probably carrying over 5 pounds of fat, which would be plenty to get you through a marathon, you just wouldn't do it very quickly.
A typical runner has about 1,500 calories worth of glycogen available for quick metabolizing. Unfortunately, a marathon takes about 4,000 calories to complete, with most of them coming from glycogen. You can eat some food during the course of a race, but your digestive system won't process it fast enough to come up with the extra calories needed, so by the end of the race, if you don't carbo-load you'll be relying on fat stores to get you to the finish. This is one way runners hit "the wall."
The solution has actually been known for decades: Build up excess glycogen supplies in the body before the race. This used to be an arduous process involving a long run just a week before the race, three days of glycogen depletion, and three days of carbo-loading. Fortunately, more recent research has found that the long run and depletion are not necessary, and may be counterproductive as they could wear you out just when you need to be restoring yourself. All you need to do is reduce your mileage (taper) and eat more carbs in the three days leading up to the race.
But how many carbs do you need? This article suggests that you need quite a lot: 3.6 to 5 grams of carbs per day per pound of body weight. I weigh 192 pounds, so that's a minimum of 690 grams of carbs in a day. Since every gram of carbs has about 3.5 calories, for me that would mean eating 2400 calories a day in carbs alone, and since it's hard to find foods that are 100% carbs, it probably means eating a lot more than that!
And there are other potential problems with a major diet change right before a big race. Your digestive system can be thrown off. If you eat a lot of high-fiber foods (which also tend to be high-carb foods) like whole wheat bread and fruit, you can get gas, constipation, or diarrhea. Not a pleasant thought halfway through your first marathon. Fortunately my diet is already fairly high in carbs, and I can increase the ratio of carbs in the diet with fairly minor changes. I can also add some foods that are just straight carbs so I don't overload with fiber. Sugar is the ultimate carbohydrate, so pancakes with lots of syrup, toast with lots of jam, and even sugary cola work fine as part of a carbo-loading diet. Yesterday I ate a huge plate of pancakes for lunch, and this morning I actually bought a 20-ounce bottle of non-diet Coke for the first time in decades.
To make sure I'm getting plenty of carbs, I decided to record everything I eat over these three days. It's actually sort of shocking when you see it all in print. Here's yesterday's menu:
1.5 cups Life Cereal
3/4 cup milk
1 glass V8
1 large banana
3 slices toast with strawberry jam
1 Nutri-grain cereal bar
1/2 cup maple syrup
1 large banana
1/2 cup raisins
The biggest plate of spaghetti I've eaten in years; about 1/3 of a pound, cooked.
1 cup marinara sauce
1 cup roasted eggplant
2 ounces mozzarella cheese
2 glasses red wine
That adds up to over 4,000 calories, and about 760 grams of carbs. Some protein and fat snuck in in a few places: The milk, the toast, the pancakes, and the pasta. The calories from carbs alone are only about 3,000. When I weighed myself this morning I was already up to 194 pounds. Yikes!
Now I'm on a plane on my way to California. I figured it would be hard to find carbs unaccompanied by fat and protein along the way, so I brought a bag of cereal bars and fruit to eat as I fly across the country. I will definitely be heading out for a run sometime this afternoon in California. It will be refreshing to get a couple easy miles in, and I'll feel better if I burn off at least some of those calories.
So far I'm finding that I'm actually fairly calm about the race that is now less than two days away. I didn't have any trouble sleeping last night; here's hoping I can maintain that calm as the race approaches.