Amanda
your nutritionist did give you excellent advice. Don't go riding on empty!
as your rides get longer, you might consider eating more earlier (although eating steaks and stuff would DESTROY me)
Before a long ride I eat a light breakfast (like oatmeal) and then 15 miles into the ride a banana. I eat smaller stuff all through the day. No big meals
until i am done, but no fasting either. And I have never bonked.

Good luck!