We've recently heard a lot about improving our health-care system, but less about improving our health—as individuals and as a nation. Although we pay the most for our health care, the U.S. has higher rates of preventable deaths from heart disease, diabetes, and stroke than almost all other industrialized nations. We have a medical-care payment system that rewards disease treatment much more than prevention.

How could doctors do better? In spite of controversy over some preventive screening (like mammograms in some age groups), we need to be clear about the proven health benefits of others. We must also better use computerized medical-record systems to remind doctors and patients to do the right things. And we need to work as a true team with nurses and other professionals to reach prevention goals.

And when we do steer patients toward proven preventive strategies, they don't always do as we suggest. The illnesses and injuries we protect against are often uncommon. Before laws discouraged it, many people never wore seat belts—and also never died in an automobile accident. Yet there is no doubt a person is at a greatly increased risk without a seat beat. Likewise, many parents recall measles as a mild illness because they've had no personal experience with the severe or fatal cases. Balancing this against often exaggerated vaccine-safety risks, they may decide not to immunize their kids. People respond to personal experience (and stories) more than statistics—we need to use both to promote prevention.

But it is lifestyle change that is of most value in disease prevention—and hardest to achieve. Occasionally, the healthy lifestyle message is easy for the doctor to explain, and for the patient to put into practice. "Wear a seat belt every time" is a clear edict that is reinforced by school teachers, public-health officials, and laws in almost all states ("click it or ticket"). It's obviously a lot harder to change more complex behaviors, like smoking. The percentage of smokers in the population has been cut in half due to the combination of public-health approaches (like warning labels on cigarettes) and new pharmacological approaches like nicotine replacement and other medicines. As a result, there are many fewer smoking-related diseases and deaths.

Perhaps the biggest challenge is persuading patients to change their behavior when they don't face any imminent threat of disease. While nearly everyone knows that adopting a healthy diet and a regular exercise program would benefit their health, it is very hard for many of us to change. Yet doing these things can reduce a person's risk of type 2 diabetes by nearly 60 percent—something no medicine yet invented can do.

It turns out that simple exhortations, even by doctors, don't help very much. We help our patients most by determining what they would like to accomplish and supporting a specific action plan. As with seat-belt use, we also need simultaneous public-health approaches to improve our nutrition and physical activity. As doctors and patients, we can press our elected representatives for health-related policy changes, like calorie labeling on restaurant menus. When I hear these decried as infringements on personal freedoms, I recall some of the children I've treated: toddlers with lead poisoning, before its removal from house paint; babies with meningitis, before present-day vaccines; and children with severe motor-vehicle injuries, before modern car seats. We should embrace both medical-care and public-health approaches that allow individuals to have the best opportunity for a longer, healthier life, on which all other freedoms rest.

What can patients do? Be clear about what you would like to do to promote your health. And if your doctor asks, "What is bothering you today?" be sure you make it clear that you also expect him or her to help protect you from things that might bother you tomorrow.

Finkelstein is a pediatrician and associate professor of population medicine at Harvard Medical School and the Harvard Pilgrim Health Care Institute.