Most people look at me bewildered when I explain to them my fueling strategy during ultramarathon training. It seems backwards at first, until the reasoning is explained.
When I do a morning run, which I do almost every day, ranging from 5 to 35 miles, I take full advantage of my low muscle glucose levels. I usually leave the house with no more than some diluted coffee, water, and a serving of honey in my stomach. This sounds silly at first but—trust me—it is very crucial to the success of an ultramarathon. I'm not a sports nutritionist, but I do know that the human body can store about 2,000 calories of glucose (ready-to-burn fuel in your body) in its muscles. At the onset of any activity that burns calories, the body tends to burn this fuel because it is the simplest to burn. As physical exertion continues, the body starts burning fat as well in attempt to avoid depleting its glucose, which is vital for other functions such as mental sharpness. God designed the human body to do amazing things. One of these things includes adaptation. If you constantly force the body to chose fat as fuel, it will become more efficient at using fat as a fuel. This is where the ultramarathon fueling strategy comes into play. In a 50-mile race, if I consume 1,000 calories and exhaust my glucose stores of approximately 2,000 calories, that leaves me well short of the energy requirements to run all 50 miles. (Probably over 2,000 calories short.) In order to avoid numerous highs and lows during a race, it is ideal to keep the body glucose levels as high as possible. If they are depleted too early, a death march to the finish line will surely ensue.
By not fueling up before my morning runs, I train my body to burn fat early and often during my morning workouts. After a while the body gets really good at turning to fat as a fuel source. In the long run (No pun intended... Oh, who am I kidding? Pun fully intended.) this helps the body preserve and stabilize its vital glucose levels. This means fewer highs and lows while on the course. I prepared like this for the Fall 50, and if you read my race report you will see I only had one low while on the course. Those of you who have run an ultra—or even a marathon—can vouch for me that only one low over the course of 50 miles makes for a much more pleasant experience than average. I really believe in this training philosophy because last year at TNF Madison I did not train like this and, although I felt like I ran a solid race, I had multiple highs and lows over the course of the race.
One thing I did not mention that needs to be recognized is when I take on really long runs of 25 plus miles I do take in some fuel and water along the way. I want my body to adapt, but I don't want to pass out on the side of the road. A quick example will help: If I am going for a 30-mile run, I would probably consumer 200 calories before I start, and take in 100 calories per hour and 40-60 ounces of water over the course of the run.
Two major challenges need to be recognized before anyone tries a plan like this one. First, you have to make sure you are taking in enough calories over the course of the rest of the days to adequately replenish and heal your body. Too many bouts like this with inadequate recovery fuel will certainly end badly. Second, it does take some getting use to. Running on empty, which is what is happening during this type of plan, is much harder. This is why I don't do it for all of my runs. If I am doing an intense speed workout I tend to fuel a little more. After all, if your training is suffering from this plan, then it's not doing its job. Also, race fueling can do funny things to the body. It is wise to “practice” fueling with the product you plan on consuming during a race. If you plan on drinking gatorade and GU, then you should incorporate these products into a couple of runs in order to test how your body will react.