I'm also very focused on this feeding-the-weight-loss task, plus in a previous lifetime I used to actually race these things, at a Cat. 2 level. But alas, twas many, many moon-pies ago. Here's what I've learned:
First, I have no quibble with anything here already posted. I will have something like a bowl of oatmeal and/or a couple hard-boiled eggs and some V8 Fusion juice an hour or two before the ride starts. If I'm riding upward to two hours or more, during the ride at maybe the one or one and a half hour mark I like a Clif Builder bar (the other ones are too hard to eat while riding) but PB&J on a dense whole wheat, multigrain bread is pretty satisfying too. Read your food labels!!! Especially take a look at the ingredients in your peanut butter. Whoever got the idea to put HFCS or sugar in it should be slathered with it and staked to an ant hill. Get the real deal.
Pre-hydrate! (Is that a word?). I'll drink at least a half a water bottle (more, if I'm comfortable with it) before I push off. Once you start to feel thirsty, it's probably too late.
The only other addition I have that I didn't see mentioned is what you do post ride (or any workout). Very important because your body is now in recovery and still burning calories at a higher rate and will continue to do so for an hour or so after you finish, and you want to make sure you're giving it quality calories to replace. Carbs, and especially simple sugars, aren't that. Protein will make your body work for the recovery by being more intensive for it to digest. Sugars and carbs go right to the spot and, carbs anyway, are preferred when actually exercising.
I've been taking a protein supplement called Platinum Hydro Whey from Optimum Nutrition based on my superior Googling skills. It's what many body builders recommend and that's my only connection to them. I'm absolutely convinced of its ability to lessen next-day muscle soreness. I recently rode 47 miles with ~3000' of climbing, and I haven't ridden more than 30 miles at a time in more than 20 years. The next day I only suffered a little soreness in my lower back and did a hilly 18 miler with little discomfort. Read what WebMD has to say about protein supplements here:
http://www.webmd.com/diet/protein-shakes
Lastly, do not, do not, do not use your appetite as a measure for how much you should eat! Use reason instead. I figure an hour of 13 to 16 mph average riding will burn 400-500 calories. Don't take it all back in afterward because you feel like 'I deserve it' or 'I'm starving' so 'how about some of that lasagna!'. Cut a melon in half, scoop out the seeds and fill it with some plain low-fat yogurt. You're welcome!
C.