Dr. Oz says there's an organ inside all of us that plays a key role in making us fat—the omentum. "This organ literally pumps chemicals into your body and it holds the secrets ... to los[ing] weight."

The omentum is the fat organ connected to your stomach that's only purpose is to catch and store fat. When the fat is stored in your stomach, your body has easy access to it. The fat then creates an inflammatory process that irritates your arteries and puts you at risk for blocked arteries.

A healthy omentum, like the one Oprah's holding, should be "lacy, like stockings," Dr. Oz says. "The omentum, you'll notice, is transparent and thin."

An unhealthy omentum, like the one Dr. Oz holds, is heavy with fat. While the omentum he's holding is thick and fatty, Dr. Oz says the person it once belonged to—who died of heart disease—was just 30 to 40 pounds overweight.

"When someone's beer bellied, you know how it gets that tense, big look? That's this," he says. "That's [the omentum] pushing up against your stomach, and it coils up in there."