Ok Governor Schwarzenegger, I think you are missing the point. There are three factors that determine your healthiness:

1. Willpower/discipline/ (i.e. if you want too!)

2. Habit (nurture)

3. Environment (income, climate, work schedule, nearby grocery stores)

Any deficiency in one factor must be made up by another. Yes, (1) is good enough if you have a lot of willpower/discipline to spare, but not all of us do. (2) is ideal, but maybe our parents didn't do such a great job. (3) allows perhaps allows you to overcome (1) and (2), but not always.