Most Americans claim belief in God but many are living as "Christian atheists," according to some pastors.

"I'm sick and tired of the fact that people can attend church for ten to 20 years and never change," said NewSpring Church Senior Pastor Perry Noble.

"Here's the deal: we believe in Jesus enough to get us out of hell but not actually enough to change the way we live and that's a problem in the church," the S.C. pastor said Sunday to his mega-congregation.

Noble launched a new series titled "Practical Atheist," borrowing the term from fellow pastor Craig Groeschel of LifeChurch.tv who preached on a similar series years back and has a book on the subject coming out this month.

Practical atheist, or Christian atheist, is defined as someone who believes in God but lives as if He doesn't exist.

Groeschel calls himself a recovering Christian atheist. He says in The Christian Atheist that "Christian Atheism is a fast-spreading spiritual pandemic which can poison, sicken, and even kill eternally."

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In concordance with the well-known LifeChurch.tv pastor, Noble began preaching on the matter on Sunday recognizing that believers may say the right things or look the part but not necessarily live as Christ followers.

Seventy-two percent of Christians claim they have made a personal commitment to Jesus Christ, according to NewSpring Church, but only 17 percent feel that the local church is necessary for spiritual growth and only one in three Christians believe God expects them to be holy. "Where's the disconnect?" the church poses.

"Jesus Christ didn't just die on the cross so we can just say a prayer and live however we want," said Noble, clad in a gray sweatshirt that says "LOVE." "He died ... so we in turn would give ourselves to him."

The area Noble feels most Christians are practical atheists in is prayer.

"I believe when it comes to prayer most Christians are actually superstitious rather than believers in the supernatural," he pointed out.

The humorous pastor expressed his belief in miracles and healings through prayer, which he acknowledged was possibly a rare belief.

At the same time, he also cautioned that sometimes God says "no" to prayers and sometimes He wants believers to obey and take action rather than just pray about it.

Noble stressed, no matter what happens – whether God says "no" or "yes" – He is still a great and glorious God because "our circumstances do not alter His character."

Practical atheism will be addressed over the course of five weeks at NewSpring. Noble warned that those five weeks will be "the most uncomfortable weeks in church" for Christians.