Study will examine exercise and appetite links

May 25, 2011

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A Murdoch university academic is investigating how and why hunger tends to increase after exercise and whether there is any way that relationship can be severed.

Dr Timothy Fairchild from the School of Chiropractic and Sports Science has received funding from the McCusker Charitable Foundation to develop the three-year project.

“Every time you exercise and burn off calories, your body will want to compensate for what it has lost which is why your appetite kicks in at some stage after you’ve exercised,” explained Dr Fairchild.

“While the combination of exercise and decreasing calorie intake should result in substantial weight-loss – like in The Biggest Loser – it is this internal compensation which results in most people failing on their diets.

“When you exercise more, your body sends hunger signals up to your brain, but if at the same time you are also trying to reduce how much you eat, these signals are amplified and you feel even hungrier. What my research will explore, is whether we can sever that relationship between exercise and appetite so that people who exercise can lose weight and keep it off more effectively.

“A number of different hormones contribute to whether a person feels hungry so we will be pinpointing each of these and looking at what happens to them during and after exercise.

“A previous study recorded a 30% reduction in food intake at a buffet-style meal in people who were injected with a certain hormone. While this was very exciting, longer-term studies (injected every day for a period of days to months) have not been as successful with this hormone. The reason for this being that the body has developed multiple fail-safe mechanisms where if one hormone starts to give ‘strange’ signals, the body simply ignores it and relies on other hormones to provide information.

“So we know we will have to look at a series of hormones to unlock the link between appetite and exercise.”

Dr Fairchild said his research would also look into how different types of exercise affected post-workout hunger and whether different hormones came into play depending on the physical activity undertaken.

Research already undertaken in collaboration with staff at the University of Western Australia has measured some key hormones in people before and after exercise as well as their food intake. This research specifically looked at whether thirst has a part to play in affecting appetite after a workout.

His studies will now focus on whether the type of exercise performed plays a role in affecting appetite after the workout and how this will affect weight status and body fat levels over the longer term.

Dr Fairchild will also be continuing his close working relationship with chemistry professor Robert Doyle from Syracuse University, in New York.

“Our work has culminated in a series of exciting studies which are investigating whether the attachment of hormones, such as insulin, to vitamin B12 will allow them to be taken as a tablet instead of having to inject them,” said Dr Fairchild, whose studies also include exercise physiology, nutritional biochemistry and metabolism.

“The advantages of being able to take medication in the form of a tablet are considerable, especially if that medication needs to be taken multiple times a day, or when people do not have suitable facilities for disposing of used needles such as in some poorer countries.

“Professor Doyle heads one of the world’s leading laboratories which specialises in being able to attach two or more compounds in certain ways so as to allow them not to interfere with one another. We will be testing whether or not that new compound works in the way it is supposed to work.”

Dr Fairchild is one of nine early career researchers in health at Murdoch University who have received funding from the McCusker Charitable Foundation.

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