The Shulchan Aruch (155:2) writes that after the morning prayers, one should make a point to eat "Pat Shacharit," which literally means, "morning bread"; in effect, this means that one should ensure to eat breakfast. The Mishna Berura (commentary to the first section of the Shulchan Aruch by Rabbi Yisrael Meir Kagan, Poland, 1839-1833) notes that there are 83 diseases that can be avoided by eating breakfast each morning. It is generally assumed, as the Peri Megadim (Rabbi Yosef Teomim, 1727-1792) writes, that to fulfill this requirement one must eat the amount of a "Ke'beitza," or approximately 2 oz.
As we saw, the Shulchan Aruch speaks of eating "Pat Shacharit," or "morning bread." Does this imply that one fulfills this requirement by eating specifically bread, and not other foods?
Chacham Bentzion Abba Shaul (Jerusalem, 1924-1998) ruled that one fulfills this obligation not only with bread, but also with other baked grain products, such as a cake or a danish, since they are considered in Halacha "Pat Ha'ba'a Be'kisnin," a type of "bread." Grain products that are prepared by boiling, such as pasta, are not considered "Pat" (bread) at all, and therefore one does not fulfill the obligation of "Pat Shacharit" with such products.
Summary: One should make a point to eat every morning either bread or other baked grain products, of a quantity of at least 2 oz.