Why not? Why couldn't or wouldn't God intervene? In that case, Jesus never came. He never died for the forgiveness of our sins. He never sent the Holy Spirit. He never commanded us to pray for the things we need, as in the Lord's prayer.
If you don't believe in a God who intervenes, you don't believe in the God of the Bible.
But what I'm still waiting for, is metmom's proof to her claim that fasting works.
There are plenty of examples of prayer and fasting in the OT. Jesus Himself fasted for 40 days in the wilderness.
I have seen people get saved as a result of people fasting. There are three people who I prayed and fasted for personally who accepted Christ.