Need some advice...

Hi!
As you may notice, I'm new in this forum. I cycle as much as possible, although not as much as many of the rest of you pros! ) I ride maybe 100 miles per week. I use cycling mainly to get in shape for other sports (such as hockey) without putting stress on my knees (as running does). Anyway, the more I cycle, the more I enjoy it and I would like to start going longer distances, but I have a question. I've been reading about the nutritional requirements for long distance cycling, so just for fun I spot-checked my diet. I am usually consuming under 1500 calories per day! Now I know that at 5'7" and 120lbs at my heaviest, I'm not going to need to eat huge amounts, but this seems low if I want to be an endurance cyclist... actually, it has me thinking about other sports too, but thats a different story. So anyway, I was wondering if anyone has any ideas about whether this is okay and if its not, what to do about it. (I am a pretty healthy eater but sometimes forget to eat, I really don't have a big appetite at all most of the time. Anyway, any advice would be appreciated!