Ken C. M. wrote:
I have come to the certain conclusion that this is a bad thing. I have
done it a couple of times now, and have not had a very good experience
with it. This morning I had time. I got up made a cup of coffee,
checked email and such, and the weather wasn't perfect but not raining
and not to chilly. So I headed out for a /fast/ ride. I have a route
that is not too long, long enough where I can get a decent workout. Its
about 12 miles and I can usually average 15.5 mph or so. Today managed
16.0 mph but when I got home my stomach was not liking the ride, or more
correctly stated not like the ride on an empty stomach.

Ken
--
The bicycle is just as good company as most husbands and, when it gets
old and shabby, a woman can dispose of it and get a new one without
shocking the entire community. ~Ann Strong


You bonked out. You stomach ran out of food to metabolize and your body
had to switch to stored fat to fuel your cycling. Sometimes your body
will continue to attempt to metabolize food you don't have which can
lead to a slight feeling of nausea. Some people bonk train on purpose,
I do sometimes, to burn more fat and improve endurance. The idea is to
head out on an empty stomach, cycling at 60% max for about an hour
(never more than 90mins, or so I've read). In theory your body will be
burning stored fat while you ride.

It's a training program that must be approached with caution as it can
have negative side effects, like your body will begin to burn muscle
mass if you ride for too long without food.

If you do want to bonk train always eat something as soon as you get
home, preferably something with protein.

If you don't, always grab a small bit before you go ride.