The acute effects of exercise on appetite perceptions, gut hormones and food intake in females

232 Pages·2017·2.01 MB·English

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The acute effects of exercise
on appetite perceptions, gut
hormones and food intake in
females
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Additional Information:
• A Doctoral Thesis. Submitted in partial fulfilment of the requirements
for the award of Doctor of Philosophy of Loughborough University.
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Publisher: (cid:13)c Nawal Alajmi
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The acute effects of exercise on appetite
perceptions, gut hormones and food intake in

females

Nawal Alajmi

A Doctoral Thesis

Submitted in partial fulfilment for the award of Doctor of Philosophy of
Loughborough University
Abstract

In recent years there has been growing interest in the role of gut hormones in regulating
appetite, energy balance and weight control. Prominent among these hormones is the
‘hunger’ hormone ghrelin which is the only circulating hormone currently known to
stimulate appetite. A variety of hormones are known to suppress appetite and notable
among these is peptide YY (PYY). Both ghrelin and PYY exist in more than one form with
acylated ghrelin and PYY representing the biologically active forms of these hormones
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i.e. the form of each hormone with the most potent effects on appetite. Many studies have
investigated ghrelin responses to exercise in male participants and some studies have also
examined PYY responses. Far fewer studies have examined ghrelin and PYY responses in
female participants and this was the primary purpose of the studies reported here.

This thesis comprises four main experimental chapters which collectively sought to clarify
whether there is any evidence to support the hypothesis that appetite, gut hormone and food
intake responses differ in female compared with male participants. A total of 123
participants took part in the studies reported in this thesis. The first of these studies was
cross-sectional in nature and compared fasting appetite, plasma acylated ghrelin and dietary
restraint questionnaire values (among other variables) in 34 males and 33 females. No
significant differences were observed between sexes for any of these variables.

In the second study, appetite, plasma acylated ghrelin and ad libitum food intake responses
to cycling exercise were examined in 13 female participants taking the oral contraceptive
pill in both the luteal and follicular phases of the menstrual cycle. Although fasting hunger
and prospective food consumption values were higher in the follicular than the luteal phase
there was no difference in appetite, plasma acylated ghrelin and food intake responses to
exercise between menstrual cycle phases.

In the third study, appetite, plasma acylated ghrelin, plasma PYY and food intake
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responses to energy deficits created via diet and exercise were compared in 13 young,
healthy female participants who completed three separate trials (control, exercise deficit
and food deficit) in a random order. The findings revealed that, as with male participants,
females experience compensatory appetite, gut hormone and food intake responses to
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dietary induced energy deficits but not to exercise induced energy deficits (over the course
of a nine hour observation period). The final study reported in this thesis compared
appetite, plasma acylated ghrelin and ad libitum food intake responses to a one hour run in
10 male and 10 female participants. Suppressions of both hunger and plasma acylated
ghrelin were noted during exercise but there was no significant difference in the responses
of males and females during or after exercise.

Collectively, the studies reported here suggest: 1) that fasting appetite and plasma acylated
ghrelin concentrations do not differ between male and female participants; 2) that appetite,
ghrelin and food intake responses to cycling exercise do not differ according to the phase of
the menstrual cycle in females; 3) that dietary restriction is more likely to elicit
compensatory feeding responses than elevated exercise levels in females and 4) that males
and females do not differ in their acute appetite, ghrelin and food intake responses to an
acute bout of running exercise. Hence the studies reported here do not support the
hypothesis that exercise will be less effective for controlling appetite and food intake in
females than in males.

Key words: exercise, appetite, food intake, ghrelin, peptide YY, gut hormones

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Acknowledgements
I wish to send my sincerest gratitude to the following people who have all had invaluable
roles to play throughout the duration of my PhD:

Firstly, to Dr. David Stensel for being a constant source of support and guidance as my
supervisor throughout my research project. He has given me the opportunity and the
approval to undertake the project and has provided me with the drive and resources
necessary to see the project through from start to finish. I hope that we can remain friends
and work together in the future to continue what we have started here and develop new,
exciting research.

I am grateful to those participants who volunteered to take part in my research. Your
dedication has very much been appreciated, without it I would have not been able to
succeed in completing my PhD.

The Master and Undergraduate students who assisted and supported me with data
collection during my PhD; these include Sophie Enever, Stephanie Edwards, Laura Harker,
Ka Chen, Christopher White, Marissa Hensen, Steph Gibb, Fiona Askew, Laura Watt,
Charlie Austin, Laura Hillyard, Konstantina Sklivagkou, Samuel Low and Cigdem Turkan.
If I have forgotten anyone I sincerely apologise – I have been working on this project for a
long time! I am ever so thankful for your help and your commitment will never be
forgotten.

Dr Rachel Batterham of University College London, for her assistance with the peptide
YY analysis in the third study in this thesis.
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Dr. Lettie Bishop and Dr. Harumi Hayashida, I am grateful to have shared a laboratory
with the both of you throughout the study of the menstrual cycle. Thank you for sharing
your expertise and knowledge with me.

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Dr. Alvaro Reischak – Oliveira for his loyalty, a wonderful laboratory partner in the year
he spent at Loughborough University. I am grateful for your assistance and for those many
memories we spent at BBQs and dining together.

To Dr. James King, my primary lab partner, I can’t express how grateful I am for having
you there as a learned colleague and friend.

For Kevin Deighton and Lucy Wasse I send my gratitude for being wonderful laboratory
partners and without your support this would not have been possible.

I of course cannot leave out Dr. Saravana Arjunan for being my best friend, my rock and
my motivation to keep going when times were tough. Without his continuous help I don’t
think I would have achieved what I was set out to do. Thank you dearly.

On a personal note, I would like to thank my good friend Zenab Farhan for supporting me
and for putting a smile on my face when times were hard and when I needed it the most.
Thank you.

For my friends who became my family here over the years I have spent in Loughborough,
thank you for giving me an experience I will never forget. Thank you for making me feel
welcomed, at home and less home sick.

I am very fortunate to have had such driven, focussed and intelligent people around me to
share ideas with, disprove theories, and help keep on track with when situations became
trying. My best wishes to all your continuing successes.

And finally I wish to thank my family, my husband Ahmad and my beautiful sons Hamad,
Mohammed, Salem, Abdul - Mohsen and Abdul – Rahman for their love, support and
understanding for all the long nights I had to spend working. I love you dearly.

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Preface
Conference communications and presentations
Abstracts from the following studies have been peer reviewed and have been accepted for
conference presentations as follows:

Alajmi NS, De Oliveira AR and Stensel DJ (2011) Acute effects of exercise on appetite,
energy intake and plasma acylated ghrelin concentrations in males and females. Journal of
Sports Sciences. 29 (Supplement 2): S108.

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List of Abbreviations
The abbreviations mentioned below are used throughout this thesis. They will be
mentioned in full in the text and then abbrevaited throughout the thesis.

a-MSH (alpha-melanocyte stimulating hormone)
AG (acylated ghrelin)
AgRP (agouti related protein)
ANOVA (analysis of variance)
ARC (anorectic arcuate nucleus)
AUC (area under the curve)
BMI (body mass index)
CART (cocaine and amphetamine regulated transcript)
CCK (cholecystokinin)
CNS (central nervous system)
DBP (diastolic blood pressure)
DPP-IV (dipeptidyl peptidase IV)
EDTA (ethlenediamine tetra-acetic acid)
EE (energy expenditure)
EI (energy intake)
FSH (follicular stimulating hormone)
GABA (gamma-amino butyric acid)
GH (growth hormone)
GHS-R (growth hormone secretagogue receptor)
GI (gastro-intestinal)
GLP-1 (glucagon – like peptide-1)
kcal (kilocalorie)
kJ (kilojoules)
LH (luteinizing hormone)
NPY (neuropeptide Y)
OCP (oral contraceptive pills)
OXM (oxyntomodulin)
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PFC (prospective food consumption)
POMC (proopiomelanocortin)
PP (pancreatic polypeptide)
PYY (peptide tyrosine tyrosine)
RMR (resting metabolic rate)
RPE (rating of perceived exertion)
RQ (respiratory quotient)
SBP (systolic blood pressure)
SD (standard deviation)
SEM (standard error of the mean)
SPA (spontaneous physical activity)
SPSS (Statistical Package for Social Sciences
TAG (triacylglycerol)
TEF (thermic effect of foods)
TFEQ (three factor eating questionnaire)
VAS (visual analogue scales)
VO max (maximum oxygen uptake)
2

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