A small car offers less protection in an accident than a large car does, but since a smaller car is more maneuverable, it is better to drive a small car because then accidents will be less likely.
The argument that 'A person who exercises vigorously every day has less body fat than an average person to draw upon in the event of a wasting illness. But one should still endeavor to exercise vigorously every day, because doing so significantly decreases the chances of contracting a wasting illness' employs reasoning most similar to that employed by the argument above.