It really depends what sort of exercise you're doing. I go to the gym four or five times a week and try and get out on my bike at least once on the weekend. If I do eat before exercise I always make sure it's something light and, if possible, a couple of hours before I hit the gym otherwise I get stitch. Aim for high protien foods if you're doing intense exercise as this will help you to repair your muscles.
There is so much conflicting advise on what you should eat and when. You just have to find something that works for you. On week days I tend to go to the gym for an hour or two on the evening. Usual breakfast is a slice of toast and a banana. Lunch is a salad. For dinner I usually go for an egg white omelette, small portion of pasta, crust less quiche, soup etc. I usually have a banana or smoothie mid way through the afternoon as a snack. It gives me enough energy to get through the gym and keeps the hypos at bay.
Em