The influence of environmental temperature on appetite-related hormonal responses

Background: Acute exercise in the heat has been shown to reduce appetite. However, the influence of exercise in the cold on appetite regulation remains unclear. The aim of this study was to compare exercise-induced appetite regulation under three different environmental temperatures. Methods: Eleven male participants completed three experimental trials on the following separate days: exercise in the heat (36 degrees C), exercise at neutral temperature (24 degrees C), and exercise in the cold (12 degrees C). The exercise trials consisted of pedaling exercises for 30 min at 65% of maximal oxygen uptake (VO2max). Blood samples were collected repeatedly to determine plasma ghrelin, peptide YY (PYY) and other hormonal concentrations. Subjective feelings of hunger and tympanic temperature were also monitored. Results: Tympanic temperature was significantly higher in the 36 degrees C trial than that of the other two trials (P < 0.05). The subjective feelings of hunger in the 36 degrees C and 24 degrees C trials were significantly lower than those in the 12 degrees C trial (P < 0.05). Plasma ghrelin concentration decreased significantly with exercise in all conditions (P < 0.05), and the responses were not significantly different among the three conditions. Plasma PYY concentration increased significantly after the exercise in the 24 degrees C trial only (P < 0.05), with no significant difference among the three trials. Conclusions: These results suggest that exposure to hot or cold temperatures during exercise did not affect exercise-induced plasma ghrelin and PYY responses. However, the exercise-induced reduction of subjective hunger was significantly attenuated in a cold environment.