The effect of brisk walking in the fasted versus fed state on metabolic responses, gastrointestinal function, and appetite in healthy men

OBJECTIVE: To investigate the effect of brisk walking in the fasted versus fed state on gastric emptying rate (GER), metabolic responses and appetite hormone responses. SUBJECTS/METHODS: Twelve healthy men completed two 45 min treadmill walks, fasted (FASTED) and followed consumption of a standardised breakfast (FED). GER of a standardised lunch was subsequently measured for 2 h using the (13)C-breath test method. Blood samples were collected at baseline, post-breakfast period, pre-exercise, immediately post exercise, pre-lunch then every 30 min following lunch for 2 h. Circulating concentrations of acylated ghrelin (GHR), glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY), pancreatic polypeptide (PP), glucose, insulin, triglycerides, non-esterified fatty acids (NEFA) and cholesterol were measured. Subjective feelings of appetite were assessed at 15 min intervals throughout. Substrate utilisation was measured every 30 min, and continuously throughout exercise by indirect calorimetry. RESULTS: No differences were observed for GER T(½) (FASTED 89 ± 22 vs. FED 89 ± 24 min, P = 0.868) nor T(lag) (FASTED 55 ± 15 vs. FED 54 ± 14 min, P = 0.704). NEFA concentrations were higher in FASTED at pre-exercise, post exercise and 30 min post exercise (pre-lunch) (all P < 0.05) but no differences were observed for glucose, cholesterol or triglycerides. Carbohydrate oxidation was greater at all time-points during FED exercise (all P < 0.05). Minimal changes in appetite were observed post lunch ingestion with no differences in PYY or GHR observed between trials. GLP-1 concentrations were greater in FED post-breakfast and pre-exercise (P < 0.05), though no differences were observed after lunch. A greater concentration of PP was observed in FED from pre-exercise to 30 min post lunch consumption (all P < 0.05). Insulin concentrations were higher in FED pre-exercise but higher in FASTED 1.5 h post lunch (P < 0.05). CONCLUSION: These findings suggest that gastrointestinal function, hunger and appetite regulatory hormones are not sensitive to low-intensity bouts of physical activity and holds positive implications for weight management practices.