how to prevent deadly diseases before they start

It's scary to find out you have a life-threatening disease like diabetes. But now, doctors can diagnose prediseases — early versions of dangerous conditions — so that you can beat them back before they take hold. One in three Americans has a predisease, but since they generally cause few, if any, symptoms, detection is crucial. What you need to know:

Prediabetes
More than 50 million American adults have prediabetes — defined as a fasting blood glucose level between 100 and 125. You're more likely to have it if you've gained more than 11 pounds since your 18th birthday, you rarely work out, you have a family history of diabetes, and/or you've had gestational diabetes.

• Why it's risky: There's a 30 percent chance that within three years of being diagnosed with prediabetes you'll develop diabetes — a disease that occurs when cells can't properly use the hormone insulin to transport sugar through the blood — which can damage virtually every organ in the body.
• What to do: You can reduce your risk of progressing to diabetes by more than half by dropping 7 percent of your body weight, no matter what you weigh (if you're 170 pounds, say, that means losing 12 pounds). Also, if you add two-and-a-half hours of moderate-intensity exercise a week, plus keep fat calories to 25 percent of your daily intake, your diabetes risk practically disappears.

Prehypertension
A blood pressure reading said to be "normal" less than five years ago — a top number from 120 to 139 or a bottom one from 80 to 89 — is now considered prehypertension, says William J. Elliott, M.D., a professor of preventive medicine at Rush University Medical Center in Chicago.This condition affects one out of three American adults.

• Why it's risky: You have up to a 37 percent chance of progressing to hypertension, or high blood pressure, within four years of being diagnosed with prehypertension. Having high blood pressure at age 40 puts you at a threefold risk of dying from a heart attack compared with a woman with a healthy reading.
• What to do: Limit sodium intake to 2,400 mg or less daily by sticking to fresh and/or low-sodium foods. This not only lowers your odds of developing hypertension but also cuts your risk of having a heart attack by 25 percent. Losing 15 pounds over four years or less will also reduce your risk of high blood pressure.

Read more: How To Prevent Diabetes, Hypertension, And Other Diseases - Redbook