Appetite regulation is important for maintenance of a healthy body mass. Vigorous exercise suppresses appetite and this is associated with lower levels of the ‘hunger hormone’ ghrelin and increased levels of the hunger suppressing hormone peptide YY (1-5). These patterns have only been examined in the short term and research has yet to explore the effect of successive days of exercise. This study compared appetite perceptions, energy intake and appetite regulatory hormones on two consecutive days of vigorous intensity exercise.Fifteen healthy, physically active men (18-24 y) completed two, 2-d trials (exercise and control) in a crossover design. The exercise trial involved a 1-h treadmill run at 70% VO2max, in a fasted condition, on the morning of each trial day followed by 6-h of rest. The control trial involved 7-h of rest on each trial day. Ad libitum meals provided at 2 and 6-h on each trial day and an ad libitum snack bag for the overnight period were used to assess energy intake. Seven blood samples were collected during each trial for the measurement of acylated ghrelin, total peptide YY and insulin by ELISA, and triglycerides and glucose by enzymatic, colorimetric measures. Appetite was assessed at 30-min intervals using visual analogue scales.Data were analysed via two-factor (time x trial) repeated measure ANOVAs and paired sample t-tests using SPSS version 21.0 for Windows. Significance was set at P<0.05, n=15 unless otherwise stated. Values are expressed as mean±SD (text) or mean±SEM (figure). Energy intake did not differ significantly between the control and exercise trials (6983±957 vs. 6921±796 kcal/trial (31-h)). Area under the curve (AUC) values for hunger and prospective food consumption (PFC) were lower in the exercise vs. the control trial (hunger: 531±148 vs. 610±173, PFC: 606±140 vs. 687±161) while AUC values for fullness were higher in the exercise trial (772±102 vs. 685±152) (all P<0.05). Acylated ghrelin and total PYY (n=14) did not differ significantly between trials (Figure 1). There was an interaction effect for triglyceride (P=0.036), suggesting a trend for lower concentrations at the end of day two on the exercise trial. AUC glucose concentrations were significantly higher in the exercise vs. the control trial (69±4 vs. 65±6 mmol/L/trial (14-h)), partly due to a glucose spike in the exercise trial after the first buffet meal (3-h) on day two (6±1 vs. 4±1 mmol/L, P<0.001). AUC Insulin concentrations were lower in the exercise vs. the control trial (1414±425 vs. 2065±878 pmol/L/trial (14-h)), with lower concentrations in the exercise trial before the first buffet meal (2-h) on day two (16±6 vs. 29±10 pmol/L, P<0.001).These findings indicate that there is no compensation for energy intake or alterations in appetite regulatory hormones across two consecutive days of exercise.