Well, it's not necessarily "bad" that you're not eating enough, it just really isn't good. It's bad if you're losing weight that you're not meaning to, but if you're hovering at a steady weight and you're not losing muscle and replacing it with fat (visual check) then you're probably still eating enough for your body to maintain its composition. (Keep in mind that I'm saying this with a grain of salt.)
If you're in relatively good health, I would say to just keep working out at a moderate rate. If you're wasting away, on the other hand, then it may be time to make a change to something.