These effects are mediated via several mechanisms, including reduced nutrient intake and/or absorption, enhanced L cell secretion of gut peptides such as GLP-1 and peptide YY (PYY), changes in the levels and composition of bile acids, and potentially decreased secretion of unidentified duodenal factors that may promote insulin resistance and/or have detrimental effects on ß cell secretion (9–11). This evidence concerns the gene PYY and Insulin resistance.