When assessing the health benefits of dietary fiber, there are three fiber characteristics (solubility, viscosity and fermentation) that correlate well with beneficial effects on clinical measures (cholesterol, blood glucose, blood pressure and body weight) of Metabolic Syndrome.Insoluble fiber (e.g.wheat bran) can have a mechanical stimulatory effect on colonic mucosa, delivering a laxative benefit if the particles are of sufficient size and coarseness, but insoluble fiber does not provide a significant benefit for clinical measures of Metabolic Syndrome.For soluble fiber, it has been well established for over 3 decades that viscosity is directly proportional to metabolic benefits, such as cholesterol lowering and improved glycemic control (high viscosity =significant improvement in glycemic control and cholesterol lowering).Based on fiber viscosity and degree/rate of fermentation, soluble fiber can be divided into three clinically meaningful categories: 1) Soluble non-viscous (e.g.inulin, oligosaccharides, resistant starches, wheat dextrin): dissolves in water, no significant increase in viscosity =no significant metabolic benefits, rapid gas formation, and energy harvest (calorie uptake) from fermentation by-products;2) Soluble viscous / readily fermented (e.g.β-glucan, guar gum, gum Arabic, karaya gum): increased chyme viscosity improves glycemic control by slowing carbohydrate degradation and glucose absorption,delivering nutrients to the distal ileum to stimulates mucosal L-cells to release metabolically active peptides (e.g.GLP-1);viscous chyme also captures and eliminates bile, stimulating bile production which results in lower serum cholesterol;readily fermented by colonic bacteria (gas formation, energy harvest from fermentation by-products);and 3) Soluble viscous /non-fermented (e.g.psyllium): increased chyme viscosity drives improved glycemic control and cholesterol lowering as above, but the lack of fermentation results in no appreciable calorie harvest from fermentation by-products (improved weight management), and the viscous gel remains intact throughout the large bowel, driving a stool normalizing effect (softens hard stool in constipation, firms loose/liquid stool in diarrhea).The optimal fiber therapy for Metabolic Syndrome would be a highly viscous and non-fermented soluble fiber,and would provide clinical benefits that include cholesterol lowering, improved glycemic control, sustained weight loss and lower blood pressure.