Basically, Oatmeal goes through a process that rolls the oats. Oat Bran on the other hand, goes through a process that flattens the groats and ends up seperating the bran from the flour.
Typically, Oat Bran has much more fiber and protein than Oat Flakes. Both have the same amount of fat and calories though.
Oatmeal and Oat Bran have Fiber, which regulates the digestive system and helps pass waste and toxins out the body. It absorbs fat and cholesterol that would otherwise make its way into the blood. Depending on your age, you should eat between 21 grams and 38 grams of fiber everyday.
Eating either for breakfast can help you with a heart healthy, fat lowering, completely safisfying way to start the day!