Take a guess at how much each these five factors affects your health:  the quality of the medical care you get; the genes your parents pass on to you; the environment (viruses, chemicals, etc.); your social circumstances, such as your income and education levels; and your behavior (related to diet, exercise, alcohol, tobacco, and so forth).

Or simply try putting them in order from most important to least important.

People often assume that these factors come into play in the order I’ve listed them:  medical care first, genetics next, and so on.  But in fact, it’s the opposite.  That is, people’s actions related to what they eat, drink and smoke -- and how much activity they get – have the biggest influence on their health.

The amount and quality of medical care account for only 10-20 percent of health differences. But behavior accounts for 35-50 percent of the difference in health between people who are otherwise similar.

This reality can be hard to believe.  After all, more than one dollar out of every six in the U.S. economy goes for medical care – how can it possibly be true that this spending affects only 10-20 percent of the difference between good health and poor health?

Money aside, it’s still hard to buy this picture.  If you go to the hospital because you have pneumonia or were in a car accident or have a heart attack, it seems obvious that getting good medical care can make the difference between living and dying.  So why doesn’t medical care show up in the numbers as having a bigger impact?

The answer has to do with the sheer volume of day-to-day living we do, in contrast to the volume of medical crises and medical care the typical person experiences. For example, compared to most people, I have used a high volume of high-intensity medical care in my life, with eight hospitalizations totaling about 33 days (almost all, I am happy to say, more than 20 years ago).  But those 33 days are a very small fraction of the more than 22,000 days that I’ve been alive.  And most people are eventually disabled by, and die of, chronic conditions such as diabetes and heart disease.  What do you think has a greater impact on my chances of developing diabetes or heart disease – the 33 days I spent in the hospital, or my actions around diet, exercise, alcohol, and tobacco the rest of the 22,000 days of my life to date?

Of course, it makes sense to take steps to get good medial care.  But it’s usually what you do when your doctor isn’t looking that makes the biggest difference between poor health and excellent health.