You'll keep your weight down. The standard American diet -- high in saturated fats and processed foods and low in plant-based foods and complex carbohydrates -- is making us fat and killing us slowly. According to the Centers for Disease Control and Prevention (CDC) and a division of the CDC, the National Center for Health Statistics, 64 percent of adults and 15 percent of children aged 6 to 19 are overweight. Eating a vegetarian diet is low in fat and keeps you slim.