The protection is attributed to a lowering of insulin levels. Insulin is a hormone that helps the body store fat and use glucose, the body's main food source.
Elevated insulin increases the risk for diabetes, a major risk factor for cardiovascular disease.
The study shows that fiber may keep individuals from gaining weight. However, the study does not change the American Heart Association's dietary recommendation that individuals should get 25-30 grams of fiber a day from food, not supplements. It appears that most of the study subjects consumed far less fiber from food than recommended by the association. During digestion fiber increases the transit time of food throughout the gastrointestinal tract, which may decrease the absorption of calories. However, these findings may also be partly due to a more active lifestyle found among those with a high fiber intake.