Oats, eaten as oatmeal (porridge), are a popular breakfast choice. Oatmeal is fairly low in calories and a great source of fiber, particularly a soluble fiber called beta-glucan. Oatmeal’s filling power comes from its high fiber content and its ability to soak up water. Soluble fiber, such as the beta-glucan in oats, can help you feel full. It may also help release satiety hormones and delay the emptying of the stomach.