Originally Posted by
Machka
The better shape you're in, the less you need to eat. As you get into shape, your body improves its processing methods of whatever fuel it has.
Also ...
The theory is that if you are eating normally, you should have about 2000 calories in storage in your liver and muscle cells. Assuming that you're burning approx. 500 calories per hour, theoretically you should be able to ride for 4 hours before you've used up those 2000 calories. I can cover about 68 km in 4 hours right now, but back in the day when I was fast, I could cover 100 km in 4 hours.
Eat a 500 calorie breakfast before you go out, and you might be able to ride for 5 hours without food.
However, if you're still building up your fitness, and if your body doesn't process fuel efficiently, you'll probably manage about 2 hours before you start to feel it ... the early stages of a bonk.
Therefore, we recommend that people consume approx. half what they burn if they are on rides longer than 2 hours ... 200-300 calories per hour. If they eat that much, they won't bonk, and they will have the energy to complete the ride. Later, after having done many longer rides and feeling comfortable with longer distances people may discover that they can get away with less food ... and that's OK. After you're comfortable with longer distances, you can adjust your fuel as you see fit.
However, it is a good idea to have 200-300 calories available on a ride, whether you eat it or not. You just never know when you're going to encounter a bigger hill or stronger winds ... or maybe you're just not feeling particularly energetic. I've gone into the early stages of a bonk at some really odd places and times ... and thank goodness I had a granola bar on board.
As for riding long distances (ultra endurance stuff), it can be very important to start eating 200-300 calories right at the beginning and keep eating it as long as you can. Back to the 2000 calories you have in storage. Over a 4-hour period if you consume nothing, your 2000 calories is gone. But if you are eating 250 calories per hour, at the end of 4 hours you should still have 1000 calories to work with. In my ultra endurance days, I found that breakfast + approx. 250 calories per hour worked up to about 6-7 hours, and then I needed to stop for a meal. I was OK again (still eating 250 calories per hour) for about 4-5 hours, and then I needed to eat another meal, and so on until the end of the ride.
Fabulous post [MENTION=4588]Machka[/MENTION].
In my training notes, I have written down that your average cyclist has 1600 cal of stored glycogen. My guess was that was based on a 175 pound male and scaling that down for me at 135 pounds, I have used the working assumption that I have about 1200 cal of stored glycogen.
I also am not a hammer type rider, I ride long distances at a moderate effort for the most part and am rarely out of breath on a ride. I think I burn about 400 cal/hr, given my size and riding effort.
My third factor that I consider is that I think I am very well conditioned to my typical ride length/effort.
So considering that I would usually eat about 200 carb cal before I head out for a typical 4hr ride, I figure I have 3-4 hours of stored glycogen, so starting eating at the 2hr mark should leave me a good safety margin. Last weekend, I knew I was doing a tougher/longer ride and ate about 400 carb calories prior to the ride and 1000 carb calories on the bike. I didn't really think this through beforehand, but now I can see that I cut things a little close, by my own calculations (which admittedly are very approximate), I left myself at the end with only 100 carb calories or 15 min of riding. I was pretty tired at the end, which I thought related to the effort expended (maybe I was right) but maybe I was running out of calories too.
Thinking this through right now is a great exercise for me because I'm soon riding a century ride which will be tougher than my normal rides and I will probably ride it a little harder than usual. I think I will make point of eating a little more, I'll have to work out the math on it.
H