Your body runs on sugar. Period. Doesn't matter the source, except it really does. You can get it directly from sugar, by eating a candy bar. You can get it from carbs such as wheat, potatoes, rich, anything starchy. Or you can get it from fat.
Unfortunately, you can't actually digest fat. Your stomach can't deal with it. But the bacteria which live in your intestines can. So, you eat fat two days before the ride. You eat carbs the day before the ride. Then you eat sugary foods the day of the ride.
If you have no stored fat, like most serious cyclists, you HAVE NO CHOICE but to run off of eaten food. If you run out of that energy, you are DEAD IN THE WATER. Can't emphasize that enough.
Now, if you have stored fat, you can actually run off of that. You have to get your body to start digesting itself. As you might expect, your body does not do that lightly. When you get to the point where you need stored fat, your body will try to convince you to STOP doing whatever you're doing. You will become tired. You will become listless. You will become depressed. You will question why the hell you ever set out on the ride.
If you push through, your body will start to burn stored fat. If you have no stored fat, your body will start to burn muscle. This is extremely bad for your health, which is why your body will try to stop you. Push through only if you have stored fat.
Moral of the story: bring food unless you're trying to lose weight; in which case do not eat food (because that will stop the process of burning fat).
posted at: 20:54 | path: /life | permanent link to this entry