This Lent, fasting is for a cause. Chris Seay, for example, published A Place at the Table, a 40-day diet in solidarity with the poor. Blood:Water Mission is promoting its Forty Days of Water which began on Ash Wednesday.

I've eaten a solidarity diet, and—for someone like me who likes bread and red meat—it is a painful lesson on the suffering that roughly a billion people experience. But I'm afraid that by making the Lenten discipline of fasting about a cause, we are caving in to our cultural distaste for self-denial.

Modern Christians, along with our culture, dislike the idea of exerting control over our bodies, simply for denial's sake. The popular book Eat, Pray, Love wouldn't have sold so well if it had been titled Fast, Pray, Serve. As a result of our culture's unease regarding abstaining from things our bodies desire, we must justify fasting by doing it for a good cause. But as we relearn to fast, we should remember that these disciplines are very much about us and our own personal faith, not only about solidarity with a cause.

Neuroscience sheds light on how fasting and other spiritual disciplines work by training our subconscious mental processes. We think of ourselves as entirely the activity of our conscious thoughts. In reality, our brain has thousands of sub-conscious processes going on all the time. These processes are often pushing and pulling different ideas, concerns, or cravings into our consciousness. What this means is your conscious self is far less in control over who you are and what you do than you realize.  "We are not the ones driving the boat of our behavior," says neuroscientist David Eagleman. "Who we are runs well below the surface of our conscious access."

Fasting can train and shape these processes, giving us the ability to exert control over other desires. One study found that students who intentionally practiced good posture for two weeks showed significant improvement afterward on measures of self control. The ability to control our relationship to food is, of course, one of the most difficult of the disciplines. Self control is like a muscle; it can be exhausted by overuse, but it can also be strengthened with exercise.

Jesus expected that dietary restriction would be a part of our spiritual practice. "When you fast," he said, not if. The traditional practice for Lent is to fast on Ash Wednesday and the following Wednesdays, Fridays, and Saturdays throughout the next 40 days. Fasts, of course, don't require abstinence from all food. A fast might mean a vegetarian diet, but it should require some extra level of dietary control.

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Fasting and all other spiritual disciplines are not simply reminders of other more important things. We may use hunger like a string tied to our fingers, prompting us to pray or consider the plight of the poor. But more importantly, spiritual disciplines shape us in deep ways. Because our brains—at the very least—mediate, process, and experience our spiritual lives, the disciplines can train us to become more attuned to God himself. Fasting then teaches and enables us to live by deeper truths and in accord with a deeper reality than the basic cravings of our bodies.

For example, when our blood sugar runs low, chemical signals from the blood stream reach the brain, which sends out signals to eat. This can happen whether or not your stomach is empty. We obey those cravings and grab a snack—perhaps without ever consciously deciding to eat it.

Similar processes occur in social situations, when we interpret bodily cues to determine if a new acquaintance will become a friend; when we study and can't figure out a problem until we've slept on it; or when a hunch leads us to a friend's house even when we couldn't remember the precise directions. The subconscious brain is at work, guiding our actions and our behavior.

This subconscious self is not wholly uncontrollable. It can be trained and shaped. Fasting and other spiritual disciplines train these processes, shape them, and thereby shape us into spiritual people. Fasting schools our subconscious. We exert our will over the cravings of our body so that we have a mental process in place that is strong enough to overrule other temptations we face. We slowly become people who are less driven by temporary cravings, whether for food or sex or personal fulfillment. While spiritual disciplines shape who we will be, they also reveal who we are. As we struggle and often fail—week after week—we discover our true selves. We learn about our weaknesses and can seek forgiveness.

If fasting for the poor raises awareness of their plight and spurs us to action alleviating their need, it is certainly a beneficial endeavor. But there is tremendous value in self-denial for its own sake. Or rather, a habit of denial strengthens our ability to take up the cross as even our very bodies are molded into the likeness of Christ.

Rob Moll is an editor at large for Christianity Today and author of What Your Body Knows about God, due out from InterVarsity Press in 2013.

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Related Elsewhere:

Christianity Today has many more articles on Lent and Science & Health. Recent articles on Lent include:

Giving Up Self-Discipline for Lent | There is really only one 'lesson' I've learned in the penitential season. By Mark Galli (Feb. 22, 2012)
What People Gave Up For Lent 2012 (According to Twitter) | Chocolate and social media once more top the list. And folks seem to have given up giving up Bieber. (Feb. 27, 2012)
The 'Above All' Commandment of the Sabbath | The one divine 'law' that tells us to stop striving for transformation. (Mar. 16, 2012)
Why Ash Wednesday Belongs out of the Church and out on the Streets | We suspect that penitence is usually done best when one joins in a community. By Lauren Winner (Feb. 22, 2012)