I cant help you on the first one at all... except that I always feel quite a bit fuller when I eat larger proportions of veggies too...
I'm sure Wattage and the other girls will be better able to answer this question, but I *think* the lean-back type ones are called recumbant bikes. Personally, I find them kind of useless unless im just warming up. I get bored, and it feels impossible to get a real work out from them.
On the other hand, I LOVE the "traditional" bike. I take my spin classes on these and they give you a killer work out. You have to use your core muscles to stay stabilized and reduce bouncing while pedaling, you can properly pedal on them (meaning, you use your leg muscles to push the pedal down, and pull it up, as opposed to just pushing the pedal down and letting momentum bring it back up), AND you have the option of several pedaling positions (sitting, standing, hovering, etc).
Ive found my thighs and butt have toned up incredibly since I've been spinning....I wouldnt say that they have slimmed down to an insane degree, but muscle has replaced the fat that was once there (plus, I'm apple shaped, so my thighs have a tendency to be reasonably trim anyway..)
Anyway, hope that helps some!