After breakfast? I would include breakfast as well. My energy levels after a breakfast of bacon and eggs is far steadier than after any breakfast cereals, toast, muffins, pastries, etc. Avoiding any large carb intake (post workout _possibly_ excepted) is key to steady energy levels.
For a more rational book, try Robb Wolf's "The Paleo Solution", which also has an extensive chapter on sleep and cortisol management.
Obviously this varies person by person. In my own personal experience, I have found that eating carbs in the morning (a reasonable amount) allows me to have a much stronger workout. When I eat NO carbs, it makes it too difficult to maintain a moderate to intense workout schedule. I liked Paleo as well, but I liked Ferris' attempt to look at the "whole body".
If you are indeed engaging in significant activity, then the carbs will help. I have sedentary job (technical) but get in a good couple of hours at the gym most days. Keeping carbs moderated keeps the fat in check, but cutting it too low make intense cardio and strength training very challenging (and less productive).
Cereals seem to do near nothing (Even those 'healthy' ones or heavier ones like muesli with honey) for me aside from satisfying the 'I'm hungry' feeling which quickly dissipates anyway. The times when I've had a good breakfast (Bacon and eggs, yoghurt and fruit, etc) is when I've felt the best.
For a more rational book, try Robb Wolf's "The Paleo Solution", which also has an extensive chapter on sleep and cortisol management.