Is it permissible to fast while consuming suhoor after the Fajr adhan, on the premise that the adhan is recited approximately 45 minutes before true dawn?

It is not possible to determine the validity of the fast for those who ate after the Adhan (call to prayer) because it is unknown whether the Adhan coincided with the true dawn (Fajr as-Sadiq) or preceded it.

Fasting is tied to the true dawn, which is the horizontal, spreading whiteness in the horizon, whose light increases until the sun rises. Whoever eats after its appearance invalidates their fast.

Due to the difficulty of seeing the true dawn in cities, one must rely on trusted calendars.