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|Title: ||Effect of exercise and different environmental conditions on appetite, food intake and the appetite-regulatory hormones, ghrelin and peptide YY|
|Authors: ||Wasse, Lucy K.|
|Issue Date: ||2011|
|Publisher: ||© by L.K. Wasse|
|Abstract: ||The role of gut hormones in the regulation of appetite and food intake is well established. The studies presented within this thesis have examined the effects of exercise and different environmental conditions on gut hormones (acylated ghrelin and total peptide YY), appetite and food intake. Forty-two young (mean ± SEM; 22.6 ± 0.4 y), healthy and generally lean (body mass index 23.7 ± 0.3 kg m2) males were recruited into four studies.
In study one, 60 minutes of high intensity (70 % of O2 max) running and cycling exercise suppressed concentrations of the appetite-stimulating hormone acylated ghrelin to a similar extent. Study two revealed that after 60 minutes running in the heat (30 °C), hunger is lower in the pre-prandial period, and energy intake lower over the 7 h trial duration compared with a similar trial conducted in temperate (20 °C) conditions. Acylated ghrelin was suppressed during running in the temperate and hot environment but this did not appear to mediate the lower energy intake observed during the hot trial. In study three, energy intake tended to be higher after 60 minutes running in a cool environment (10 °C) compared with a temperate (20 °C) environment. During and shortly after running in the cold, perceived ratings of fullness and satisfaction were lower. Acylated ghrelin concentrations appeared to be suppressed to a lesser extent during running in the cold which could mediate the elevated energy intake observed at the first meal. However, energy intake was also higher at the second meal in the cold trial when acylated ghrelin concentrations were higher in the temperate trial. Study four showed that energy intake and acylated ghrelin concentrations were lower, and total PYY tended to be lower, in normobaric hypoxia suggesting a possible role for acylated ghrelin, but not PYY, in mediating the decrease in energy intake observed in hypoxia.
This thesis confirms that exercise transiently suppresses acylated ghrelin concentrations regardless of the environmental conditions (temperature and altitude) exercise is performed in. The findings support anecdotal reports that appetite and energy intake are suppressed in the heat and stimulated in the cold. These responses may be partly mediated by acylated ghrelin immediately after running but other mechanisms are likely involved thereafter. Acute hypoxic exposure suppresses acylated ghrelin concentrations; an observation which may explain the decreased energy intake in hypoxia.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Sport, Exercise and Health Sciences)|
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