How our bodies marshal defenses against disease depends on many factors, such as age, gender and genetics. Recently, the role of our bodies’ biological rhythms in fighting disease has come under study by some in the medical community.

Actress Mary Tyler Moore battles it. Country singer Mark Collie has it. Rhythm and blues singer Pattie LaBelle was diagnosed with it recently. Celebrities like Moore, Collie and LaBelle are just three well-known faces amid the 16 million Americans suffering from diabetes mellitus, a chronic disease in which the pancreas produces too little or no insulin, impairing the body’s ability to turn sugar into usable energy.

More than four centuries ago, doctors were considered omnipotent, and the ethical statutes of England’s Royal College of Physicians instructed: Let no physician teach the people about medicines, or even tell them the names of the medicines, particularly the more potent ones … for the people may be harmed by their improper use.