CommunityEat a Great BreakfastHow many calories is appropriate for breakfast and what kind of breakfast helps boost your energy? in Eat a Great Breakfast How many calories is appropriate for breakfast and what kind of breakfast helps boost your energy? Jordan Z. Hmm, its a hard question. in my opinion, 300 calories is enough to fuel you. My lunch is at 10:30 though, so i dont need to be full for a long time.