Good health is to some an obssession, to others simply a good idea, and to Christians a human responsibility. Obviously, there are health problems that often prevent us from being healthy, many of them out of our control altogether, but as far as we are able we should maintain fit, wholesome bodies with which to love God, enjoy life, and spread the Gospel.
Especially in the West, however, many have made health their idol. A cursory examination of the supermarket magazine racks demonstrates that people are consumed both with their health and their image, and that they're willing to go to great lengths to maintain both. As Christians, we realize our health is largely in God's hands. That does not mean we don't have any responsibility to eat right, exercise, and avoid harmful habits.
The idea that God's grace is basically a free pass to wolf down Big Macs and laze on the couch all day is a pernicious one. God's grace frees us to behave in ways that honor Him, meaning maturely and responsibly (though of course we don't always). Where our health is concerned, that means largely taking preventative measures rather than simply reacting when problems crop up.
It's ironic that the Western world is obssessed with health, but has a fairly unstable view of it. Eastern traditions posit that if one eats right and remains active, they'll live a long time with relatively few problems. They also privilege natural remedies over synthetic drugs, herbs and teas over aspirin and Demerol. This approach is called "wholistic" because it addresses the whole person, not just symptoms.
Maybe it's because we have universally accessible health care that Europeans and North Americans just do what they feel like and head to the doctor every time they feel queasy or sore. While Eastern methods often go too far (things like acupuncture and reiki are rooted in pagan spiritualism and might need to be avoided), we could certainly learn a few things about keeping the doctor at bay in the first place.
Christian parents have a particular responsibility to instill good habits and healthy lifestyle choices in their children. They also have a responsibility to make sure their kids understand that God is ultimately the source of good and bad health, and that sometimes Providence decrees physical hardship even for those who make consistently good choices. Finally, we have a responsibility to model wise living for our kids; the following resources and curricula were chosen to help families fulfill each of these.