Berachot 10b states as follows: “R.Yitzchak said that R. Yochanan said and R.Yosei. ben R.Chanina, said in the name of R. Eliezer ben Yaakov. Each person said this halachah in the name of the Chachamim that preceded them. Mishnah Avot 6:6 says, “One who says something in the name of its speaker brings redemption to the world.”
What is the meaning of that which is written: “You shall not eat with the blood” (Vayikra 19:26)? You may not eat before you pray for your blood.
One may not eat before he prays. Others say that Rabbi Yitzchak said that R. Yochanan said that R. Yosei, ben R. Chanina, said in the name of R. Eliezer ben Yaakov: One who eats and drinks and later prays, about him the verse states the rebuke of the prophet in the name of Hashem: “And you have cast Me behind your back” (I Melachim 14:9).
Our Sages drew from this that one who sees to his own bodily needs by eating and drinking before prayer is likened to one who cast Hashem aside and is full of pride. The allusion is understood as we do not read “your back” (gavecha); but rather we read, your pride (gei’echa).
However many Rishonim debate the prohibition of eating before praying Shacharit . The debate deals with whether or not it's origin is Ktav H'Tora or Rabbinical enactment. There are essentially three practical applications (nafka minot) that result from this debate.
Ramban (Vayikra 19:26) also states that all of the cases that are learned from the pasuk of “You shall not eat with the blood...” are considered Ktav prohibitions from the Tora
Rambam in Sefer H'Mitzvot (Shoresh 9), who includes the prohibition of eating before praying as one of the prohibitions that is learned from the pasuk of “You shall not eat with the blood.."
It is clear that prohibition of eating before Shacharit is only a Rabbinical enactment. Haggahot Maimuniyyot explains that this is also why the Gemara changed the wording of the pasuk from gavecha to gei’echa.
In general, Chachamim do not change the pasuk’s wording so that they can establish a new Ktav prohibition. Thus, it is obvious that the Chachamim only intended to state that this prohibition is only Rabbinical.
Conclusion: The Sephardic view is to be stringent and to not eat before Shacharit. Consult with your local Rav or posek to understand the minhag of your community.
