If you have what's known in medical literature as a hostile personality, then you’re also more likely to have insulin resistance, which ultimately raises blood sugar, than someone with a more laid-back kind of personality.

"Hostile people are impatient and aggressive, and they feel that the world is out to get them," says Richard Surwit, Ph.D., author of The Mind-Body Diabetes Revolution and professor of medical psychology at Duke University School of Medicine in Durham, North Carolina.

That suspicious outlook appears to be associated with the body’s ability to regulate glucose levels.