The piece of diet advice I champion most is to eat for what you do. Here’s a good example of what I’m always yappin’ about.
My friend Trent just got back from a month of training down in Tucson. Like me, his main two sports are riding and climbing. Unlike me, he’s been focused more on climbing than riding. With my injury, I’ve been forced to change my concentration from cycling to climbing because it’s all I can do. Trent’s trip to the winter cycling Mecca that is Tucson got him more psyched on riding. The first thing he said when he get back was that he was getting too glycogen depleted and had to adjust his diet and eat more carbs. My diet, in turn, has changed in exactly the opposite way; I’m eating less carbs and a ton fewer calories.
A big problem with diet books—or diets in general—is that they tend to prescribe a single way to eat for all circumstances. It doesn’t take a genius to comprehend how you might need to eat more when you’re active than when you’re sedentary. But diet books that often recommend eating a certain way all the time, then backing it up with a lot of bizarre science, can cause a lot of conflict within our logical minds.
In the simplest sense, carbohydrates are fuel for the body. Your body doesn’t store them in its tissue unless they aren’t burned off and it’s forced to; in which case they are stored as adipose (or fat) tissue. So it stands to reason that you’ll want the amount that you consume, and hence the percentage of your daily calories, to change as your activity level changes.
Furthermore, you’re body can only store about an hour or so of glycogen (carbs converted into glucose, or blood sugar) in your blood and liver. So the longer you exercise the more carbohydrate you need to eat to replenish your blood sugar. If you run out of blood sugar during exercise you’re body is forced to tap into its tissues, both fat and muscle, for energy. This is less efficient, so you can’t perform as well and is referred to as “the bonk” in sporting terms. This is the reason that sports foods are loaded with carbohydrates (and better yet, sugar, which speeds into your system the quickest—bad at other times but good during sports).
Long, steady exercise, like cycling, requires a lot of carbohydrate replenishment throughout. If you don’t eat carbs you risk doing a lot of damage to your muscle tissue. Your body will react by first slowing you down and then forcing you to stop. Protein and fats consumed simple aren’t absorbed quick enough to do you any good during a ride. In fact, they can lead to gastric upset because they are hard to digest.
Less steady exercise, like climbing (especially bouldering and short climbs, or cragging, but not mountaineering at all), doesn’t require the same type of replenishment. Other than hiking to the crag, the work is mainly anaerobic and done in short bursts. In a day of climbing you’re not likely to extinguish you blood glycogen, even if you eat a balanced diet that is very slow to absorb, because you aren’t going at a steady state for more than an hour.
So even though they are both doing a lot of exercise, a climber can be fueled well by a diet that has a different caloric needs and ratios than a cyclist. Since the cyclist is continually burning up the calories consumed, he needs to consume more in general. And, since most of these added calories are carbs, it makes sense that two perfectly fit athletes would have vastly different macro-nutrient needs. Hence, the old diet switcharoo.
pics: beata and i ready for some pizza, bob's no-carb except beer diet; they all work, depending on what you do.