A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Master of science by research.Introduction: A strategy that combines both increasing energy expenditure and reducing
energy intake (EI) to induce a negative energy balance is key for preventing and managing obesity. Exercise has been shown to reduce EI in a subsequent meal, an increase in temperature has also been shown to decrease appetite stimulation. Exercise in a hot environment may augment the appetite suppressing effect of exercise. However, there is currently little evidence available regarding the effect of environmental temperature during exercise on appetite. This study focused on the effect of exercise in different environmental temperatures on gut hormones and EI. Methods: A total of 8 healthy males completed four 5.5 hour conditions in a counterbalanced order. A preliminary visit consisting of a submaximal and maximal exercise test was conducted prior to experimental visits. For experimental visits, participants arrived in a fasted, euhydrated state at 08:30 and were fitted with a cannula, heart rate monitor, rectal and skin thermistors before completing one of four conditions: exercise in 10°C, 20°C or 30°C or resting control. Participants ran for 60 minutes on a treadmill at 70% of maximal oxygen uptake or rested for 60 minutes before resting for 4.5 hours. Blood samples were taken at 0 (fasted), 1, 1.5, 2, 3, 4 and 5 hr. Perceptions of hunger were assessed using visual analogue scales at 0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 and 5 h. Ad libitum meals were provided at 1.5 hr and 5 hr. Results: Although there was a significant reduction in relative energy intake in all exercise conditions (p < 0.001), this was not augmented or attenuated by any change in environmental temperature. This decrease was also not supported by any decrease in acylated ghrelin or increase in PYY. Furthermore, the only significant decrease in overall appetite was stimulated by the intake of food in meal 1 (p < 0.001). There was also no significant difference in total energy intake, lending to the notion that the decrease in relative energy intake can be partially, if not completely attributed to the increase in energy expenditure from exercise. Conclusion: These results suggest that exercise produces an energy deficit through a reduction in relative energy intake, regardless of environmental temperature. Further research into the effects of exercise in different environmental temperatures in an overweight and obese population is warranted
