Graduate Thesis Or Dissertation
 

Exercise and Appetite : The Influence of Exercise Intensity on Appetite in Endurance Trained Women

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  • In endurance-trained men, an acute bout of exercise is shown to suppress post-exercise appetite and alter changes in specific appetite regulating hormones. Limited research has examined these responses in endurance-trained women. PURPOSE: To investigate the effect of exercise intensity on the appetite regulating hormones acylated ghrelin, PYY and GLP-1 and subjective ratings of appetite in endurance trained women. METHODS: Fifteen highly-trained women (18-40y, 58.4±6.4kg, VO₂MAX=55.2±4.3 mL/kg/min) completed isocaloric bouts of moderate intensity exercise (MIE) at 60%VO₂MAX, and 2) and high- intensity exercise (HIE) at 85%VO₂MAX in randomly assigned order. In both trials, subjects ran on a treadmill until an energy expenditure (EE) of 500 kcal was achieved. Blood was drawn pre-exercise (baseline), immediately post-exercise and every 20-min for the next 60-min. Plasma concentrations of acylated ghrelin, PYY₃₋₃₆, GLP-1 and subjective appetite ratings via visual analog scale (VAS) were assessed at these same time points. Food intake and physical activity were recorded 48-h before each trial. A mixed model analysis was used to examine the impact of exercise intensity (60% vs. 85% VO₂max) on appetite- regulatory hormones and VAS responses over time. Where significant effects were found, post-hoc analyses were performed using the Bonferroni correction for multiple comparisons. For these same variables area under the curve (AUC) was calculated using the trapezoid method to determine total response over time. The overall statistical significance was accepted at the 5% level. RESULTS: Results for appetite hormones showed no main effect for exercise intensity or interactive effects, but a significant main effect for time; thus, data were combined across exercise intensities for each time point. Acylated ghrelin decreased (p=0.014) and PYY₃₋₃₆ and GLP-1 increased (p=0.036, p<0.0001) immediately post-exercise compared to pre-exercise, indicating appetite suppression. Examination of AUC showed no differences between exercise intensities for acylated ghrelin (p=0.055) and PYY (p=0.54). For GLP-1, AUC was slightly higher in the MIE compared to the HIE trial (p=0.04, uncorrected). Results for appetite ratings were similar, with no differences in AUC between MIE and HIE trials for ratings of hunger, satisfied, and desire to eat. There was a trend for AUC ratings of fullness to be lower after the HIE compared to the MIE (p=0.03, uncorrected). For appetite ratings, there was a significant main effect for time, with no interactive effects. Hunger and desire to eat decreased immediately post-exercise (p=0.0012, p=0.0031, respectively) compared to baseline, and desire to eat was also higher (p=0.0031) 60-min post-exercise. Satisfied and Fullness increased (p=0.0005, p=0.0006, respectively) at 60-min post-exercise. CONCLUSION: Similar to males, post-exercise appetite regulatory hormones were altered toward suppression in highly trained women. Based on AUC data, HIE suppressed feelings of fullness compared to MIE, but did not impact post-exercise hormone response or other ratings of appetite. Since EE was held constant between MIE and HIE trials, these findings were independent of the energy cost of exercise. Thus, in highly-trained women, post- exercise appetite suppression was similar regardless of exercise intensity. For female athletes trying to optimize nutrition for endurance performance, post-exercise appetite suppression could alter the amount, type and the timing of food intake. These possible changes in post-exercise appetite need to be considered in the overall nutrition strategies recommended to active women to support athletic performance.
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