Just as you can't tell a book by its cover, you can't determine if someone's healthy or not by the way they look or seem to feel. That woman with the great body on the treadmill might have dangerously severe anemia because she doesn't eat enough foods with iron. That CEO who always seems to be in control may be suffering from extremely high levels of stress and high blood pressure-a prime candidate for a heart attack.

Your risk for illness and disease is influenced by a multitude of factors, the least of which is how you appear on the outside. It's based on the medical history of your family, your cholesterol levels, the foods you eat every day, your blood pressure, the amount of stress in your life, the number of drinks you have per week, your body fat compared to muscle-and the list goes on...