Release of peptide YY(3-36) (PYY(3-36)) has been proposed to contribute to postprandial satiety. Using a randomized, double-blind design, we examined the effects of a 417 kcal beverage with 95% of the calories from long-chain fatty acids compared to a 21 kcal lipid-free control beverage on the temporal profiles of total plasma PYY levels and appetite ratings in 12 normal-weight human subjects. Ratings were taken before ingestion of the beverage and 15, 30, 60, 120, and 180 min later. Blood samples were taken from the subjects when ratings were made. The lipid beverage increased plasma PYY relative to the control beverage at 60-180 min after ingestion. Subjects were divided into High and Low PYY groups (N=6 in each group) on the basis of a median split. In the High PYY group, the lipid beverage was more effective in suppressing hunger and enhancing satiety than in the Low PYY group, in which the lipid beverage had no effects on appetite. Within the High PYY group, changes in mean relative hunger suppression (changes in hunger specifically attributable to the lipid load) across the 3-h test closely paralleled changes in plasma PYY after ingestion of the lipid beverage relative to the control beverage. The close temporal correspondence between these variables supports the proposed role of this peptide in the intermediate-term control of intake, possibly acting to regulate appetite during the intermeal interval.