Lost the momentum to lose weight? Blame it on your omentum. Dr. Oz says the omentum is an organ that can make you fat.

Dr. Oz says instead of worrying about those extra inches around your thighs and a little junk in your trunk, you need to worry about the omentum—the fat organ inside your belly that's only purpose is to store fat.

When we talk about obesity being a risk factor for heart disease, we're actually wrong," says Dr. Oz. "It's not all obesity, because fat thighs don't give you a bad heart. [The omentum] does."

When the fat is stored in your stomach, your body has easy access to it, Dr. Oz explains. The fat then creates an inflammatory process that irritates your arteries and puts you at risk for blocked arteries.

The omentum is also to blame for beer bellies. Some people tend to store their fat around their waists—giving them a beer belly or an "apple-like" shape. While others store fat around their hips, making them "pear"-shaped. Apple-shaped people are more at risk for heart disease than pear-shaped people.

"If your waist size is more than 35 inches and you're a woman—or 40 inches for men—you have a major risk factor for heart attacks because this [omentum], instead of being an inch thick, is now five inches thick, and you don't even see it." If you have trouble remembering these exact goals, just remember that your waist should be no more than half your height.

"This is the first time I've been happy about being a pear!" Oprah exclaims.

More keys to a long life from Dr. Oz, America's Doctor.