I too eat a low calorie diet for weight loss and cycle. What I fnd works for me, is to target my calories to support my cycling. By all means have a good breakfast before you go out on the bike (for me ~300 cal of carbs and low fat protein are good, i.e. a boca burger on a whole wheat english muffin). If I was only going to ride 12 miles I wouldn't eat anything extra, but I would probably drink gatorade if its hot out. I think you are overestimating how many calories you are burning. I think its a lot closer to 600, which is good for weight loss. If I were going to do a longer ride, I would drink gatorade throughout the ride (which can add substantial calories) and then take a gel say after 20 miles if I felt like I needed it. For a long ride, maybe a powerbar at mile 40, etc. After the ride, I'd eat a healthy low cal lunch, again to support my weight loss since now the exercise is finished BTW, that's terrific on your weight loss to date, and great that you want to take your exercise program up a notch! So, yes you do need to eat a little more to support your cycling, but much less than you think if you goal is continued weight loss.