Olive oil is thought to be healthy because it's mostly monounsaturated fat. But cold-pressed extra-virgin olive oil may have an extra benefit: it appears to be more filling than other fats. That's according to research presented at a German symposium on fat. Researchers started by feeding 120 volunteers a daily, 18-ounce serving of low-fat yogurt. But mixed in the yogurt were three tablespoons of extra-virgin olive oil, canola oil, butter, or lard. Turns out volunteers in the olive oil group reported feeling more full during the three-month study period. And they had larger concentrations of serotonin in their blood—a signal of satiety. The researchers say extra-virgin olive oil contains aromatic compounds that block the absorption of glucose from the blood, delaying the recurrence of hunger. Indeed, study subjects who ate yogurt with just olive oil extract consumed fewer calories over a three-month period than those who ate plain yogurt. And they finished the trial with less body fat too. Which leads these researchers to conclude that olive oil extract could be key to creating a better low-fat snack: tastes great, more filling.