I receive lots of questions and comments from long distance riders about nutrition. Often times they want to know what I use during my ultra events and 24-hour races. Many are surprised to hear that my strategy generally involves relying solely on liquid nutrition and very little if any solid foods. Here are some thoughts...
During a ride over 2 hours like Amtrak or the Bear, you will definitely be burning more fatty acids than glucose to produce energy. This is where you want to be for a century.
The body can store about 1,200 to 1,900 Kcal worth of glycogen, a substance deposited in the muscles and liver as a store of carbohydrates. It is a polysaccharide that forms glucose on hydrolysis. If you are producing energy and expending about 600-900 Kcal an hour on the bike, that means you will burn through this store in 1.5 to 2.5 hours. From that point on, your primary source of energy will come from stored fatty acids. Even an extremely trim pro athlete has about 80,000 to 100,000 Kcal of stored fatty acids that can be converted to energy. But fatty acids will not give you the instant surge of energy; it burns at a different rate. Think of the difference being like kindling wood and a heavy log. The kindling is easily ignited, burns quickly, and yields a lot of heat energy (glucose---sugars). The heavy log will burn at a slower rate (fatty acids). Over time the log has much more potential for producing energy.
"Bonking" is thought to be caused by an increase in serotonin. The rising levels of serotonin are caused by increased delivery of tryptophan to the brain. This increase in free tryptophan in the blood is due to the increase in free fatty acids in the blood. There are some who think that this is one of the causes of "central fatigue". To make matters worse for the endurance cyclist, the brain’s production of dopamine (the neurotransmitter responsible for generating feelings of excitement, reward, motivation, and pleasure) begins to drop even as serotonin levels are rising, which can be the cause of the voices in your head telling you "I cannot do this thing" and having your attitude go negative.
One of the best way to help avoid bonking is to reduce the intensity of exercise (that pacing thing again). While proper fueling will help, finding a manageable pace is more important.
Regarding fuel, you should still take in calories to help replenish your glycogen stores, but after ~two hours when most glycogen is gone, your body turns into a fat-burning machine. There have been cyclists who have ridden extremely long distances (over 500 miles) without eating anything. They had to stay hydrated, but they took in no calories.
So...what to eat? I have seen pro mountain bike riders eating some weird stuff during races: Pop Tarts, cookies, pastries, candy bars, trail mix, pizza. Hey, you can't argue with success. But I have also seen some of these same pro riders drop out of long-distance events because they were feeling sick.
When you are doing a century, try to avoid "comfort foods". Yes, you are a fat-burning machine, but you want to try to ingest foods that are rapidly assimilated and will not spike insulin levels. This typically means staying away from simple sugars. Bananas, energy gels, some energy bars, fruit chunks (like melon), carb replacement drinks, energy blocks all work.
Here are a few tips:
- Don't assume that the rest stops will have food items that are good for you, or agreeable with your system. Carry most of your calories on board in a jersey pocket. (Side note: OCW always has fresh fruit at their rest stops). I use 3x5 ziplock bags I get from Office Depot or Staples.
- Take in calories while on the bike. Your water bottles should contain a supply of calories whileg hydrating and also include some electrolytes.
- No more than about 250 calories an hour. Remember: less is better.
- A mix of carbs and proteins (4:1) is beneficial for longer rides.
- Avoid Whey as a protein source during exercise; Soy is much better. Whey is a cheese byproduct and breaks down quickly when warmed up; after about two hours, the sports drink mix with whey protein in your bottle will taste like spoiled milk.
- Avoid whole grains and fiber if you can. No need for unplanned pottie breaks.
- Do not overdo it (eating that is).
- Do not eat for three hours before the event. If the event starts at 8 AM, don't wake before 5 just to eat. Your sleep is more important than ingesting calories.
- Start fueling as soon as you get warmed up on the bike.
- Track your intake.
- Caffeine (if your system can tolerate it) will help your body metabolize fatty acids. This is why many of pro riders drink espresso.
- Experiment with fueling during training. Do not experiment during the event. Know what works for you, and stick to it.
If you want to try it, you can carbo-load. You will need to start early enough though; the process generally takes 1-2 weeks. Gorging yourself on pasta the night before won't do it. In a nutshell, for a two week loading schedule, take in more proteins than carbs for the first 5 days (40/60 carb to protein ratio). Then go 50/50 for four days. Then switch to a 60/40 ratio of carbs to proteins to finish out week 2. I usually do a one week load for centuries and a two week load for races. Remember that loading will only add minutes of stored glycogen. Not real helpful for a seven or eight-hour event.
Here is a link to an article by Carmichael Training Systems (CTS) that talks about the three most common nutrition mistakes athletes make. If you read anything, read mistake #1.