Millions of Americans suffer from chronic diseases-cancer, diabetes, depression, obesity, mental illness, and many more-and traditional medicine is failing to bring them back to health. Doctors write prescriptions to combat symptoms but, all too often, don't even try to solve the root cause of the condition.

In Just Be Well, Dr. Tom Sult points the way toward a new path. He and a growing number of physicians practice functional medicine, a discipline that treats people, not diseases. Functional medicine doctors ask "Why do you have this illness?"--not "How can we stem the...