Figure 1.

The complex relationship between dietary fiber intake, the gastrointestinal tract and host metabolism. Viscous fibers increase gastric emptying rate, may inhibit nutrient absorption and contribute to SCFA fermentation. These effects may lead to a reduced postprandial glucose appearance and an increased release of incretin and satiety-stimulating hormones (GLP-1, PYY), which might influence energy intake and peripheral tissue metabolism. Prebiotics modulate microbiota composition and SCFA production thereby affecting energy homeostasis and insulin sensitivity. Insoluble fibers are most effective in increasing colonic transit time thereby possibly affecting microbiota composition, and vice versa microbial metabolites may stimulate colonic motility. Solid lines indicate well-studied effects of dietary fiber, dashed line indicate more controversial findings. Abbreviations: SCFA short-chain fatty acids; GLP-1 glucagon-like peptide 1; PYY peptide YY.