Sprint interval exercise improves several health markers but the appetite and energy balance response is unknown. This study compared the effects of sprint interval and endurance exercise on appetite, energy intake and gut hormone responses. Twelve healthy males (mean(SD): age 23(3) years, body mass index 24.2(2.9) kg.m -2 , maximum oxygen uptake 46.3(10.2) mL.kg -1 .min -1 ) completed three 8h trials (control (CON), endurance exercise (END), sprint interval exercise (SIE)) separated by 1 week. Trials commenced upon completion of a standardised breakfast. Sixty minutes of cycling at 68.1(4.3)% of maximum oxygen uptake was performed from 1.75-2.75h in END. Six 30s Wingate tests were performed from 2.25-2.75h in SIE. Appetite ratings, acylated ghrelin and peptide YY (PYY) concentrations were measured throughout each trial. Food intake was monitored from buffet meals at 3.5 and 7h and an overnight food bag. Appetite (P<0.0005) and acylated ghrelin (P<0.002) were suppressed during exercise but more so during SIE. Peptide YY increased during exercise but most consistently during END (P<0.05). Acylated ghrelin was lowest in the afternoon of SIE (P=0.018) despite elevated appetite (P=0.052). Exercise energy expenditure was higher in END than SIE (P<0.0005). Energy intake was not different between trials (P>0.05). Therefore relative energy intake (energy intake minus the net energy expenditure of exercise) was lower in END than CON (15.7%; P=0.006) and SIE (11.5%; P=0.082). An acute bout of endurance exercise resulted in lower appetite perceptions in the hours after exercise than sprint interval exercise and induced a greater 24h energy deficit due to higher energy expenditure during exercise.

Appetite and the orexigenic (appetite stimulating) gut hormone acylated ghrelin are acutely suppressed during strenuous endurance exercise (1) . Additionally, energy deficits induced by such exercise do not appear to elicit compensatory increases in appetite, acylated ghrelin and energy intake in the subsequent 24 h, resulting in a negative energy balance (1) . Recent evidence suggests that low volume sprint interval training may act as an alternative to endurance exercise as a time-efficient method of improving aerobic fitness (2,3) and cardiovascular disease risk factors (3,4) . However, the appetite, hormonal and acute energy balance responses to such exercise are unknown and may have important implications regarding the effectiveness of such exercise for weight management. This study investigated the appetite, acylated ghrelin and 24 h energy intake responses to 30 min low volume sprint interval exercise compared with 60 min traditional endurance exercise.Twelve healthy male volunteers (mean (SD); age 23 (3) years, body mass index 24.2 (2.9) kg.m, maximum oxygen uptake (VO 2 max) 46.3 (10.2) mL.kg) completed 3, 8 h trials separated by one week in a counterbalanced Latin Square design. Participants arrived at the laboratory at 8.45 am after an overnight fast and the 8 h trial commenced upon completion of a standardised breakfast meal (72.9% carbohydrate, 9.5 % protein, 17.6 % fat). Sixty min of continuous cycling exercise at 68.1 (4.3) % of VO 2 max was performed from 1.75-2.75 h in the endurance exercise trial (END). In the sprint trial (SPR), exercise was performed from 2.25-2.75 h and consisted of six 30 s cycle sprints with 4 min recovery after each and 3.5 min warm-up and warm-down periods. No exercise was performed in the control trial (CON). Appetite ratings (5) and plasma acylated ghrelin concentrations were measured throughout each trial. Food intake was monitored from a cold buffet meal at 3.5 h, a hot buffet meal at 7 h and an overnight food bag.The net energy expenditure of exercise was significantly higher in END than SPR (631 (100) vs. 142 (12) kcal; P < 0.0005). All appetite perceptions (hunger, satisfaction, fullness and prospective food consumption) changed over time (P < 0.0005). Trial · time interactions (P < 0.0005) revealed lower appetite in SPR than CON at 2.75 h (P £ 0.001). Appetite was higher in SPR than END at 5, 5.5 and 6.5 h (all P £ 0.001). Ad libitum 24 h energy intake did not differ between trials (CON: 3093 (744); END: 3238 (766); SPR: 3088 (713) kcal). Relative energy intake (energy intake minus the net energy expenditure of exercise) was significantly lower in END than CON (P = 0.006) and tended to be lower in END than SPR (P = 0.082; CON 3093 (744); END 2607 (774); SPR 2946 (714) kcal). A main effect of trial revealed higher acylated ghrelin concentrations in CON than END and SPR (both P £ 0.01). A trial · time interaction effect revealed lower acylated ghrelin concentrations in END and SPR than CON at 2.47 h and in SPR than CON at 2.75 and 3.5 h (all P £ 0.002).Sprint inter...