According to lead singer Mark Hall, "If We Are the Body" was originally written for use as a "teaching tool" in his youth group. Hall, a youth pastor, said that "[the youth group had] forgotten what the body of Christ looked like" and commented that "The world is well aware of what the church is against, but they aren’t always aware of what it’s for. Everybody in the body of Christ is given gifts to minister with; and when Christians aren’t using these gifts, the body suffers". Hall's inspiration for writing the song came from the second chapter of the book of James, where the writer "admonishes" readers to "steer clear of giving preferential treatment to any one particular group over another, such as favoring the rich over the poor".
"If We Are the Body" is a song with a length of three minutes and fifty-eight seconds. It is set in common time in the key of F♯ minor and has a tempo of 126 beats per minute. Mark Hall's vocal range in the song spans from the low note of B1 to the high note of A2. A CCM song, it has an acoustic rock sound and incorporates the violin, mandolin, and accordion in its arrangement. Featuring "energetic instrumental spurts and tight melodies", the song "admonishes the church for giving preferential treatment to any one particular group over another" and questions why the church does not minister impartially. The song's chorus, which references the Christian concept of the body of Christ, asks "If we are the body, why aren't his arms reaching?/Why aren't his hands healing?/Why aren't his words teaching?/And if we are the body?/Why aren't his feet going?/Why is his love not showing them there is a way?" "If We Are the Body" challenges the church to welcome outsiders and to "get more visibly involved in changing this world".
"If We Are the Body" was released to Christian AC and Christian CHR radio on July 26, 2003 as the lead single from Casting Crowns' eponymous debut album. It debuted at number thirty-seven on the BillboardHot Christian Songs chart for the chart week of August 23, 2003 and dropped off the chart the following week. The song re-entered at number thirty-seven for the chart week of September 6, 2003, In its seventh chart week, "If We Are the Body" advanced to number twenty-four and in its tenth chart week, it advanced to number seven. In its twelfth chart week, "If We Are the Body" reached its peak position of number three on the Hot Christian Songs chart. It also peaked at number three on the BillboardHot Christian AC chart and spent three weeks atop both the Radio & Records Christian AC and Christian CHR charts.