The most virtuous and versatile component of the oat resides in its outer layer—the bran. The bran contains a high content of a unique type of soluble fiber called beta-glucan, which has some remarkable health properties, and is incredibly beneficial for weight loss.
Because of its high fiber content, oat bran satiates you. As soon as you ingest it, the fiber in oat bran soaks up saliva and then expands in the stomach, making you feel quite full, quite fast. It provides a prolonged feeling of fullness, so you eat less in between meals.
Oat bran also blocks the absorption of calories from the intestine. When you eat food, it is broken down into its individual components of fatty acids, carbohydrate and amino acids. The calories from these components are then absorbed into the body. But when you eat oat bran, it mixes with water in your intestine to produce a gel-like substance called bolus. The bolus absorbs some of the breakdown products, and then it is attacked by gastric juices and stomach acids that turn it into a pulp. This pulp becomes part of the stool, and thereby carries the calorie-dense components of fats, glucose, and amino acids out of the body through the stool. This process both slows down the assimilation of sugar (glucose) and removes calories from the body while keeping your blood sugar levels low and stable.