There is a Halacha that states that one should not eat before davening in the morning. This is learned out as an אסמכתא, which means that it has its basis from a Pasuk in the Torah.
The verse is לא תאכלו על הדם which means that one should not eat “on” the blood. This is an awkwardly worded sentence that is explained in the Gemara as follows: It is inappropriate for one to pray for “his blood”, which means, his very existence when he has a full belly.
It is not right to eat a hearty meal before praying to Hashem.
It is viewed as an act of haughtiness to first worry about satisfying one’s physical needs before praying and putting G-d first.
The only time one is allowed to eat before prayers is when he knows that he will not be able to concentrate unless he eats or drinks a little. This can also apply to one who is old or sick and he needs to eat. Otherwise, it is forbidden to eat or drink before praying each morning.