THE COSTS OF providing medical care in America, it is frequently noted, have skyrocketed in the recent past, and promise to continue doing so in the future. There is, of course, at least a partial solution to this problem, one involving little or no expenditure of either public or personal funds. This solution calls for an increased emphasis upon preventive medicine: exercising and dieting today help to avert heart disease tomorrow; not smoking now increases the likelihood of avoiding lung cancer later.