Americans are flabby. According to the Centers for Disease Control and prevention, 33 percent of U.S. adults and 16 percent of children have a body mass index of 30 or more, qualifying them as "obese."

What's more, the incidence of obesity has risen over 100 percent since 1980, prompting the CDC to label the trend an epidemic.

But more than our physiques are soft and getting softer; our faith is as well.

From muscle to fat

Although nearly 80 percent of Americans identify themselves as "Christian," the Pew Forum reports that fewer than 40 percent attend church weekly and just over half consider their faith "very important" in their lives. In a recent study of the beliefs, behaviors and lifestyles of the major faith groups in the U.S., the Barna group found that two-thirds of Americans are "minimally active born again Christians [or] moderately active but theologically nominal Christians."

In short, the majority of American Christians don't take their faith very seriously. They either fail to integrate their faith into life or hold beliefs that are counter to its core doctrines.

But how did the muscular faith, sown with the blood of martyrs 2000 years ago, turn so flaccid?

Philosophy professor John Lamont offers an explanation by way of sociologist Rodney Stark et al. In the calculus of the typical person, the "benefits" of religion are in the future, but the "costs" are paid up-front. Hence:

... [they] are prone to backslide, to get behind on their payments....Thus, other things being equal, people will always be in favor of a modest reduction in their costs. In this fashion, humans begin to bargain with their churches for lower tension and fewer sacrifices. They usually succeed, both because it is those with the most influence—the clergy and the leading laity—who most desire to lower the level of sacrifice and because each reduction seems so small and engenders widespread approval. (emphasis added)

But despite the popularity of incremental reductions, they have not proven to have any lasting, positive effects for the Church; nor have they lightened the load and made life easier for church leadership.

Ironically, the churches with the lowest expectations for members are those with the most precipitous declines in membership. For example, in the much cited 2008 American Religious Identification Survey, membership in traditionally less demanding denominations (Methodist, Lutheran, Episcopal) declined up to 21 percent between 1990 and 2008, while the membership in more demanding churches (Pentecostal and Evangelical) rose up to four-fold in the same period.

Even churches with significant numerical growth, like the 20,000-member Willow Creek, have found that spiritual growth is lacking. And while most pastors recognize that spiritual immaturity is one the biggest problems in the Church today, few have formally defined what a mature Christian "looks like," and fewer still have established a process for spiritual formation that is intentional, structured, and woven into the fabric of church life... Continue reading here.