Peptide Y-Y (PYY) is an anorexigenic hormone implicated in appetite control, and beta-glucan is a fiber known to affect appetite. We hypothesized that plasma PYY levels would increase in overweight human adults consuming increasing doses of beta-glucan. The objective was to test whether the effect could be seen with beta-glucan delivered through extruded cereals containing a high beta-glucan oat bran with demonstrated high molecular weight and solubility. Fourteen subjects consumed a control meal and 3 cereals of varying beta-glucan concentration (between 2.2 and 5.5 g), and blood samples were collected over 4 hours. Analysis of raw PYY data showed a trend toward significant increases over 4 hours. An increasing dose of beta-glucan resulted in higher levels of plasma PYY, with significant differences between groups from 2 to 4 hours post test-meal. Data for the area under the curve analysis also approached significance, with post hoc analysis showing a difference (P = .039) between the control and the highest dose of beta-glucan (5.5 g). The PYY levels at 4 hours were significantly different between the control and high-dose meal test (P = .036). There was a significant dose response, with a positive correlation between the grams of beta-glucan and PYY area under the curve (r(2) = 0.994, P = .003). The optimal dose of beta-glucan appears to lie between 4 and 6 g, with the effects on PYY mediated by viscosity and concentration. Meal-test studies examining a range of hormones should measure hormones over a minimum of 4 hours and record meal intake for even longer time frames.