Many a student of the Japanese language will very quickly learn the words for "breakfast," "lunch," and "dinner." However, what isn't discussed is the very, very small cultural difference between the origin of these words. In meaning, the terms are used practically interchangeably - but there is one small detail.
The "asa" in "asagohan" means "morning." With the "gohan" being rice, of course. It's clearly a meal one eats in the morning.
However, "Breakfast" is derived from "break" and "fast." When one eats breakfast, they are breaking their fast.
With this in note, remember.. you can eat at noon in an English-speaking country and still be eating "breakfast." But in Japanese you would definitely be eating 「昼ご飯」 (Noon Meal, Lunch).