Peptide YY (PYY) and ghrelin have been associated with the regulation of energy balance. The objectives of this study were to determine whether total ghrelin and PYY after a standardized meal predict appetite scores and ad libitum energy intake (EI) and to examine the relationship between total ghrelin and PYY and postprandial energy expenditure (PEE). Twenty-five premenopausal women (age, 50.4 +/- 2.0 years; body mass index, 23.5 +/- 2.2 kg/m(2)) were studied. Total PYY, total ghrelin (enzyme-linked immunosorbent assay), EE (indirect calorimetry), and appetite scores (visual analogue scales) were measured fasting and every 30 minute for 3 hours after the ingestion of a standardized breakfast. Ad libitum EI was measured at lunch with a buffet-type meal. Peptide YY increased (P < .001) and total ghrelin decreased (P < .001) after breakfast. Significant changes in EE (P < .001) and appetite scores (P < .001) were noted postprandially. Appetite scores were consistently associated with ad libitum EI at lunch (r = -0.51 to 0.40, P < .05), whereas no association between EI and prelunch total ghrelin and PYY was observed. Finally, partial correlation analyses revealed that total PYY was a significant independent correlate of PEE at 60, 90, 120, and 150 minutes (r = 0.37-0.51, P </= .05). These findings provide evidence that appetite scores are better correlates of EI than are circulating levels of total PYY or ghrelin and that total PYY could be involved in the regulation of PEE.