The Role Of Blood Glucose In Exercise-induced Appetite Suppression.

INTRODUCTION: Blood glucose concentrations are known to affect hunger perceptions and appetite hormones following nutrient ingestion. Further, exercise-intensity dependent effects have been demonstrated on blood glucose and appetite separately. PURPOSE: To examine the potential role of blood glucose as a potential mechanism for appetite suppression following exercise of differing intensities. METHODS: Ten recreationally-active males and females (8 male, 2 female; 25 ± 5 y; 22.6 ± 3.2 kg·m-2; 47.8 ± 8.0 mL·kg-1·min-1; females in the early follicular phase of their menstrual cycle) were recruited for a within-subjects randomized crossover experimental design completing three separate sessions; 1) No-exercise control (CTRL); 2) 30 min moderate-intensity continuous training (MICT) run at 70% V̇O2max; or 3) running sprint interval training (SIT) with 4 x 30-s “all-out” efforts interspersed with 240-s recovery. Acylated ghrelin, active peptide tyrosine tyrosine (PYY), active glucagon-like peptide-1 (GLP-1), blood glucose, and overall subjective appetite perceptions were measured pre-exercise, as well as 0, 30, 60, and 120 min post-exercise. RESULTS: Blood glucose exhibited a main effect of session (P = 0.023) with differences existing between CTRL and MICT (4.6 ± 1.0 vs 5.0 ± 1.0 mmol·L-1; P = 0.056). Additionally, blood glucose concentrations demonstrated a main effect of time (P = 0.034) where 0 min post-exercise concentrations (5.5 ± 1.2 mmol·L-1) different compared to 30 min (4.7 ± 1.2 mmol·L-1; P = 0.027) and 120 min (4.7 ± 0.7 mmol·L-1; P = 0.089) post-exercise, likely driven by exercise-induced elevations. Acylated ghrelin was suppressed post-exercise following SIT compared to CTRL at all time points (>153 ± 82 pg·mL-1; P < 0.017) and MICT at 30, 60, and 120 min (>177 ± 48 pg·mL-1; P < 0.025). Though there were no exercise-induced effects on active PYY (P > 0.212), active GLP-1 was elevated 30 min post-MICT (6.71 ± 2.50 pmol·L-1) versus CTRL (5.20 ± 2.15 pmol·L-1; P = 0.006) and SIT (4.97 ± 2.39 pmol·L-1; P = 0.062). Overall appetite perceptions were consistently suppressed following SIT compared to CTRL (>12 ± 2 mm; P < 0.010) and MICT (>11 ± 2 mm; P < 0.012). CONCLUSION: Blood glucose does not appear to be involved in exercise-indued appetite suppression.