The Okinawan diet is made up of tofu, vegetables and fish. But a ritual they do before each meal also contributes to their health. "Okinawans recite 'hara hachi bu,'" Dr. Oz says. "[It's] an adage that reminds them to stop eating when they're 80 percent full."

"Hara hachi bu. That's what I need to do," Oprah says. "And how do you know when you're 80 percent full?"

"Well, the reality is, and many of you have experienced this, if you eat what you normally eat in a meal, you'll feel really full about 15, 20 minutes later," Dr. Oz says. "The only way to really know you're going to be 80 percent full is to stop eating way before you think you're going to be full."

More health secrets from Dr. Oz, America's Doctor
As a reminder, always consult your doctor for medical advice and treatment before starting any program.