MP's point is to get those calories in during or immediately after the ride.
Eating those exercise calories is important - but the timing is important as well. If you wait until later to ingest those calories, the benefits from all that exercise are going to diminish. Those are the calories that wind up on your gut or on your butt.
I'm in your same situation. I managed to gain about 6 pounds in the last few months
but I've been falling into that "I burned thousands of calories today so I can eat whatever I want this evening" trap.
But by not eating enough during and immediately after the ride, what I've been doing is effectively putting my body into a short-term starvation mode, so that when I did pig out later in the day my metabolism did not burn those calories but instead converted them into fat.
As a result, I found out yesterday that my body fat percentage is 33.9. Gaaaahhhhhhhh. 
So I'm going to take mp's advice and load up on the calories right before, during, and within about 30 minutes after my rides, and go easy on the pigouts thereafter.
Check out this article. While it's geared towards runners rather than cyclists, the concepts are similar.
http://www.enduranceptc.com/images//weightlossmd.pdf
Last edited by jobob; 03-08-2009 at 09:39 AM.
2009 Lynskey R230 Houseblend - Brooks Team Pro
2007 Rivendell Bleriot - Rivet Pearl