Fasting (going without something, usually food) is often connected with the season of Lent.
Why?
Lent looks forward to Christ’s sacrifice on the cross and his resurrection from the dead. It’s considered a season of preparation.
Joel 2:15 (MSG)
Blow the ram’s horn trumpet in Zion!
Declare a day of repentance, a holy fast day.
Repentance + prayer + fasting = good preparation.