Riveting insights from a rock-star doc . . .

Nobody gives you more compelling answers to body questions than the charismatic Mehmet Oz, MD -- a regular on The Oprah Winfrey Show, RealAge expert, and coauthor of blockbusters YOU: The Owner's Manual and YOU: On a Diet. Here are his tips on how to become an expert on your own body.

Become the World Expert on Your Body
That's one of Dr. Oz's top goals for everyone. And a key way to meet it is to be fearless about asking questions about anything: poop, sex, your genes -- or the waist size of your jeans -- coffee, Alzheimer's, anything.

For instance, ask Dr. Oz if there's any way to delay aging and here's what you get: "The truth about aging is that you -- right now -- have the ability to live 35 percent longer than expected, with a greater quality of life and without becoming feeble. While relying on the talents, skills, and knowledge of others may get you out of medical jams, what you really want is to avoid these in the first place. Weight training and getting quality sleep are two of nature's best anti-aging medicines.

"But just because you've made mistakes in the past -- had burgers for breakfast or fried your brain cells with stress -- doesn't mean you can't reverse them. Your body is remarkable. You can have a do-over if you want to. Within three months of changing an aging behavior, you can measure a difference in your life expectancy."

Here are Dr. Oz's no-frills answers to 7 niggling questions:

Q. Are "floaters" dangerous to my eyes?
A. Not usually.

Q. Do sit-ups strain my back?
A. No, they strengthen it.

Q. Does cracking my knuckles cause arthritis?
A. Nope.

Q. What's a healthy waist size?
A. Under 37 inches for women; under 40 inches for men.

Q. Is cancer ever contagious?
A. Sort of, but rarely and indirectly. Liver and cervical cancers as well as lymphoma can be caused by organisms that are themselves contagious.

Q. What's the best kitchen cure for diarrhea?
A. Chicken soup with rice.

Q. Can coffee help prevent Alzheimer's?
A. Yes, and Parkinson's too.

Got questions? Visit the YOU Doctors Center.