Answered by Shaykh Amjad Rasheed
Is eating suhoor (predawn meal), enough to take the place of the intention to fast?
Merely eating suhur (the pre-dawn meal) is not enough to take place of the intention to fast. Rather, the thought of fasting that day of Ramadan has to be brought to mind.
As it is said in the Tuhfa of Ibn Hajar:
And eating the predawn meal is not enough to take its place (i.e. the intention); even if:
a. he meant by it to strengthen his body for the fast,
b. he abstained from eating anything that would invalidate his fast, out of fear that dawn will come in;
as long as the fast didnt come to his mind according to the conditions that have to be met in making the intention.
[Translated by Sr. Ruqayyah Ahdab]