Effects of Oat Beta-Glucan and Thylakoids from Spinach on Satiety

222 Pages·2017·3.55 MB·English

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LSU Doctoral Dissertations Graduate School
2015
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Candida Joan Rebello
Louisiana State University and Agricultural and Mechanical College
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Rebello, Candida Joan, "Dietary Strategies to Influence Appetite: Effects of Oat Beta-Glucan and
Thylakoids from Spinach on Satiety and Reward-induced Eating Behavior" (2015). LSU Doctoral
Dissertations. 1469.
https://digitalcommons.lsu.edu/gradschool_dissertations/1469
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DIETARY STRATEGIES TO INFLUENCE APPETITE: EFFECTS OF OAT
ΒETA-GLUCAN AND THYLAKOIDS FROM SPINACH ON SATIETY AND
REWARD-INDUCED EATING BEHAVIOR

A Dissertation
Submitted to the Graduate Faculty of the
Louisiana State University and
Agricultural and Mechanical College
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy
in
The School of Nutrition and Food Sciences

by
Candida Joan Rebello
Bachelor of Law, University of Mumbai, 1986
M.S., Louisiana State University, 2012
December 2015
ACKNOWLEDGEMENTS

To my parents, family, and mentors - until we reach an age where thoughts can
adequately be expressed in words “thank you” will have to do. My husband Keith thinks he
should be getting a Ph.D. in psychology and I could not agree more! For all the times I was
overwhelmed and inundated, he was the voice of reason. For all the times I was filled with joy,
he was there to share it with me. My greatest inspiration is my mother. She had a stoic,
resilience, and calm that was hard to beat. She is long gone but never forgotten. My sister Ida
cornered the genes for these traits; but, she is the one I have always turned to, since I was little,
and to this day.
I met Dr. Carol O’Neil, several years ago when I started studying nutrition, and she was
the undergraduate advisor. Word had it that she was a “no nonsense task master” and I did not
discover otherwise! Nevertheless, if mentoring means honing of skills, an ear to listen, and a
push in the right direction, she did it all. Beneath that tough exterior is someone who cares. My
training in research has been under the guidance of Dr. Frank Greenway, and I could not have
been more fortunate. In his calm unobtrusive way he has guided me while allowing me the
freedom to think independently, and the opportunity to flourish as a scientific writer. I would
never have come this far without his gentle prodding or the myriad opportunities he has sent my
way. I am grateful to Drs. Ronald Amen, Georgianna Tuuri, John Finley, and Jenna Kuttruff for
agreeing to serve on my committee and committing to the time it takes to do so.
My education and work experience can best be described as eclectic. After studying law
and doing a stint as an international flight attendant, I embarked on a career in nutrition and
dietetics. It has all been a wonderful learning experience, and I am grateful to the people who
have touched my life along the way.
ii
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ............................................................................................................ ii
ABBREVIATIONS ........................................................................................................................ v
ABSTRACT .................................................................................................................................. vii
CHAPTER 1. INTRODUCTION ................................................................................................... 1
Dietary Fiber ............................................................................................................................... 3
Oats .............................................................................................................................................. 4
Dietary Fat ................................................................................................................................... 5
Thylakoids ................................................................................................................................... 6
Justification ................................................................................................................................. 6
Objectives .................................................................................................................................... 8
Research Questions ..................................................................................................................... 9
Hypotheses ................................................................................................................................ 10
Strengths .................................................................................................................................... 13
Limitations ................................................................................................................................ 14
Journal Articles ......................................................................................................................... 15
CHAPTER 2. THE RELEVANCE OF APPETITE RESEARCH: A REVIEW ON SATIETY
AND REWARD-INDUCED EATING BEHAVIOR ................................................................... 16
Introduction ............................................................................................................................... 16
Appetite and Satiety .................................................................................................................. 17
Reward-induced Eating Behavior ............................................................................................. 23
Measures of Appetite ................................................................................................................ 27
Appetite: Is Evaluating it Right? ............................................................................................... 36
Conclusions ............................................................................................................................... 39
CHAPTER 3. DIETARY FIBER AND SATIETY: A REVIEW ON THE EFFECTS OF
OATS ON SATIETY .................................................................................................................... 40
Introduction ............................................................................................................................... 40
Dietary Fiber ............................................................................................................................. 43
Oats ............................................................................................................................................ 51
Oat β-glucan .............................................................................................................................. 54
Oats, β-glucan, and Satiety ........................................................................................................ 55
Conclusions ............................................................................................................................... 73
CHAPTER 4. GUT FAT SIGNALING AND APPETITE CONTROL WITH SPECIAL
EMPHASIS ON THE EFFECT OF THYLAKOIDS FROM SPINACH ON EATING
BEHAVIOR .................................................................................................................................. 75
Introduction ............................................................................................................................... 75
Gut Lipid Sensing and Appetite Regulation ............................................................................. 78
Gastrointestinal Signaling and Appetite Control ...................................................................... 80
Thylakoid Membranes ............................................................................................................... 86
Conclusions ............................................................................................................................... 98
iii
CHAPTER 5. THE ROLE OF MEAL VISCOSITY AND OAT Β-GLUCAN
CHARACTERISTICS IN HUMAN APPETITE CONTROL: A RANDOMIZED
CROSSOVER TRIAL ................................................................................................................ 100
Introduction ............................................................................................................................. 100
Methods ................................................................................................................................... 102
Results ..................................................................................................................................... 109
Discussion ............................................................................................................................... 113
Conclusions ............................................................................................................................. 118
CHAPTER 6. INSTANT OATMEAL INCREASES SATIETY AND REDUCES ENERGY
INTAKE COMPARED TO A READY-TO-EAT OAT-BASED BREAKFAST CEREAL:
A RANDOMIZED CROSSOVER TRIAL ................................................................................ 119
Introduction ............................................................................................................................. 119
Subjects and Methods .............................................................................................................. 121
Results ..................................................................................................................................... 125
Discussion ............................................................................................................................... 131
Conclusions ............................................................................................................................. 134
CHAPTER 7. ACUTE EFFECTS OF A SPINACH EXTRACT RICH IN THYLAKOIDS
ON SATIETY: A RANDOMIZED CONTROLLED CROSSOVER TRIAL ........................... 136
Introduction ............................................................................................................................. 136
Subjects and Methods .............................................................................................................. 138
Results ..................................................................................................................................... 143
Discussion ............................................................................................................................... 147
Conclusions ............................................................................................................................. 151
CHAPTER 8. SUMMARY ......................................................................................................... 152
REFERENCES ........................................................................................................................... 158
APPENDIX I. PERMISSIONS .................................................................................................. 193
Journal Articles ....................................................................................................................... 193
Reuse of Figures ...................................................................................................................... 201
APPENDIX II. INSTITUTIONAL REVIEW BOARD APPROVALS ..................................... 209
VITA ........................................................................................................................................... 213

iv
ABBREVIATIONS

5-HT Serotonin
AACC American Association of Cereal Chemists
BMI Body Mass Index
CART Cocaine-and-amphetamine-regulated transcript
CD36 Cluster of Differentiation 36
CKK Cholecystokinin
CVD Cardiovascular disease
FDA United States Food and Drug Administration
GI Gastrointestinal
GLP-1 Glucagon-like peptide-1
GPCR G-protein Coupled Receptor
HDL-C High Density Lipoprotein Cholesterol
hsCRP High-sensitivity C-reactive protein
IO Instant oatmeal
IOM Institute of Medicine
LDL-C Low Density Lipoprotein Cholesterol
NHANES National Health and Nutrition Examination Survey
NSP Non-starch polysaccharide
OEA Oleoylethanolamine
PBRC Pennington Biomedical Research Center
PYY Peptide YY
v
RTEC Ready-to-eat cereal
SO Old fashioned oatmeal
TG Triglycerides
US United States
VAS Visual Analog Scales

vi
ABSTRACT

The objective of these studies was to examine the effects of oat-based cereals and a
spinach extract, on eating behavior. The cereals compared included instant oatmeal (IO), old
fashioned oatmeal (SO), and a ready to eat cereal (RTEC), each containing the soluble fiber β-
glucan. The spinach extract containing thylakoids, the internal photosynthetic membrane of
plants, was compared with a placebo.
The first study, a randomized crossover trial compared the effect of IO and SO on
subjective ratings of satiety, with the RTEC. Subjects consumed isocaloric 150kcal servings of
the cereals in random order. Visual analogue scale ratings evaluating satiety were completed
before breakfast and throughout the morning. IO increased satiety compared to the RTEC
(p<0.05); however, SO was not as effective. The second study using a similar design compared
the effect of isocaloric 250kcal servings of IO and the RTEC, on subjective ratings of satiety and
food intake. IO increased subjective satiety (p<0.01), and decreased energy intake at lunch
compared to the RTEC (p=0.012). The content and physicochemical properties of β-glucan were
determined in both studies. IO and SO had higher meal viscosities than the RTEC. IO also
displayed higher initial meal viscosity than the RTEC.
In the third randomized cross-over trial, subjects consumed the spinach extract or placebo
in random order. Subjective ratings of satiety, liking and wanting (reward components of eating
behavior), and food intake were evaluated. Compared to the placebo, consumption of the spinach
extract increased satiety over a two hour period (p < 0.05); however, there were no differences in
measures of liking or wanting, and energy intake measured at four hours. Although not
significant, males reduced their energy intake by 126 kcals (p=0.08) after consuming the spinach
extract, compared to the placebo.
vii
In conclusion, instant oatmeal in 150kcal and 250kcal portion sizes increases subjective
satiety over four hours, compared to the RTEC; whereas, the 250kcal serving also reduces
energy intake. Initial meal viscosity of oatmeal may be an important factor influencing satiety.
While 5g of thylakoids increase subjective satiety over two hours compared to a placebo, the
reward components, or energy intake are not different.

viii
CHAPTER 1
INTRODUCTION

Eating in humans is a discontinuous process made up of meals and inter-meal intervals.
Hunger is a conscious sensation that reflects a mental urge to eat whereas the process that brings
an eating episode to an end is satiation leading to satiety, in which the perception of hunger is
inhibited. Effectively, satiety prolongs the inter-meal interval. The nature and timing of
physiologic events separately influence satiation and satiety.1 The biological drive to eat is
inextricably linked to the satiating and satiety enhancing power as well as the rewarding value of
food. Obesity results from a chronic energy imbalance; hence, controlling the urge to eat
assumes importance.
Obesity is generally defined as excess body fat; however, the level of adiposity that
constitutes obesity lacks consensus.2 The measurement of body fat using historical methods such
as underwater weighing is cumbersome and expensive, and few epidemiologic studies have
included direct measures of body fat.3 Thus, obesity is often defined as excess body weight
rather than excess body fat and a surrogate measure known as body mass index (BMI) or weight
in kilograms (kg) per square of height in meters (m) is commonly used to estimate adiposity. It is
a convenient measure to assess the adiposity status of a population over time; however, it does
not distinguish between fat and muscle mass. Moreover, height and weight are subject to
demographic shifts making them highly empirical; hence, BMI may not be the most reliable
indicator of individual adiposity status.4 Nevertheless, the United States (US) and international
standard definition of obesity is a BMI of 30 kg/m2 or above, and overweight is defined as a BMI
of 25 to 29.9 kg/m2;(5, 6) although, national organizations in some Asian countries have adopted
lower BMI cut-off points to define overweight and obesity.7
1