Can High-Fiber Foods Fight the Metabolic Syndrome?

The metabolic syndrome (MetSyn) is a cluster of signs including abdominal obesity, insulin resistance, high blood pressure, and blood lipid disturbances.  MetSyn is the quintessential modern metabolic disorder, and it affects about one third of Americans.  Many MetSyn diets recommend eating high-fiber foods, and research on the role of the gut microbiota in body weight and health tends to support this recommendation.  Yet these diets are complex, so it's difficult to attribute positive effects to the high-fiber foods specifically, and some people have questioned the benefits of dietary fiber.  Do high-fiber foods really improve MetSyn and promote weight loss?