Our study demonstrates dose-related effects of intraduodenal calcium to (1) stimulate plasma GLP-1 and PYY, as well as pyloric pressures, and (2) enhance the effects of Trp to stimulate CCK, PYY, and GLP-1, associated with greater suppression of energy intake, in males with obesity. The gene discussed is GCG; the disease is obesity due to melanocortin 4 receptor deficiency.