Why do soldiers first experience boot camp? Because they need to be taught how to push their body, overcome the desire to quit and grow beyond the pain. The mind way too often gives in before the body gives out. Likewise, why did the Apostle Paul say, “I discipline my body and make it my slave” (1 Cor. 9:27). The Christian life is not about listening to our bodies and giving into its desires (gluttony, drunkenness, slothfulness, sexual immorality), but rather mastering our bodies and making the body a slave to a biblically controlled mind. This is the difference between being controlled by the flesh or being led by the Spirit (Gal. 5). Exercise, in order to be effective, pushes the body beyond its comfort zone. Diets push the body beyond its comfort zone. These make the body your slave and no longer your master. These produce discipline. And coming full circle, discipline is essential for us to mortify sin (cf. 1 Pet. 4:1-2).