EFFECT OF POLYPHENOL-RICH DARK CHOCOLATE ON ANTHROPOMETRIC, NUTRITIONAL, BIOCHEMICAL AND PHYSIOLOGICAL MARKERS IN NORMAL WEIGHT AND OVERWEIGHT ADULTS GRACE FARHAT A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy QUEEN MARGARET UNIVERSITTY 2014 Table of Contents Abstract .................................................................................................................................. v Acknowledgments ................................................................................................................ vi List of figures ...................................................................................................................... vii List of tables ......................................................................................................................... ix List of abbreviations ............................................................................................................. xi Publications ........................................................................................................................ xiv CHAPTER 1: GENERAL INTRODUCTION ...................................................................... 1 1.1 Obesity, type 2 Diabetes and Cardiovascular diseases: The major prevailing public health challenges ..................................................................................................... 1 1.1.1 Introduction ..................................................................................................... 1 1.1.2 Overweight and Obesity .................................................................................. 1 1.1.3 Atherosclerosis and Cardiovascular diseases ................................................ 11 1.1.4 Type 2 Diabetes and Insulin Resistance ........................................................ 18 1.1.5 Role of cortisol in obesity-related complications .......................................... 27 1.1.6 Importance of prevention............................................................................... 29 1.2 Polyphenols: Overview ......................................................................................... 29 1.2.1 Definition and properties ............................................................................... 29 1.2.2 Types of polyphenols, chemical structure and food sources ......................... 31 1.2.3 Factors affecting polyphenol content in foods .............................................. 36 1.2.4 Metabolism of polyphenols: from absorption to elimination ........................ 38 1.2.5 Bioavailability of polyphenols in the human body ........................................ 40 1.2.6 Toxicity of polyphenols ................................................................................. 43 1.3 Cocoa / Dark chocolate ......................................................................................... 44 1.3.1 History ........................................................................................................... 44 1.3.2 Cocoa and dark chocolate composition ......................................................... 46 1.3.3 Cocoa and chocolate production.................................................................... 48 1.3.4 Effect of processing on polyphenol content .................................................. 51 ii 1.3.5 Bioavailability of cocoa polyphenols in the human body ............................. 53 1.3.6 Benefits of cocoa/dark chocolate ................................................................... 55 1.3.7 Difference between cocoa and dark chocolate .............................................. 56 1.4 Effects of cocoa/dark chocolate on inflammation and antioxidant capacity ........ 59 1.5 Effects of cocoa/dark chocolate on insulin and glucose metabolism ................... 68 1.6 Effects of cocoa/dark chocolate on lipid profile ................................................... 79 1.7 Effects of cocoa/dark chocolate on blood pressure............................................... 82 1.8 Effects of cocoa/dark chocolate on glucocorticoid metabolism ........................... 88 1.9 Effects of cocoa/dark chocolate on fat metabolism, body weight and obesity ..... 89 1.10 Proposed investigations ...................................................................................... 100 1.10.1 Study I: Effect of polyphenol-rich dark chocolate on insulin sensitivity in normal weight and overweight adults ........................................................................ 100 1.10.2 Study 2: Effect of polyphenol-rich dark chocolate on body weight in overweight and obese adults ...................................................................................... 103 CHAPTER 2: GENERAL MATERIALS AND METHODS ........................................... 109 2.1 Ethical approval .................................................................................................. 109 2.2 Nutritional and chemical composition of the experimental dark chocolate ....... 109 2.3 STUDY I ............................................................................................................. 112 2.3.1 Study population .......................................................................................... 112 2.3.2 Determination of sample size ...................................................................... 113 2.3.3 Study design ................................................................................................ 114 2.3.4 Justification for the chosen methods ........................................................... 117 2.3.5 Data collection and processing .................................................................... 119 2.3.6 Compliance and diet diaries collection ........................................................ 134 2.3.7 Statistical analysis ....................................................................................... 136 2.4 Study II ............................................................................................................... 136 2.4.1 Study population .......................................................................................... 136 2.4.2 Determination of sample size for the small scale study .............................. 137 2.4.3 Estimation of sample size for a larger study based on Study II results ....... 137 2.4.4 Study design ................................................................................................ 138 2.4.5 Justification for the chosen methods ........................................................... 140 iii 2.4.6 Data collection and processing .................................................................... 142 2.4.7 Compliance and diet diaries collection ........................................................ 151 2.4.8 Statistical analysis ....................................................................................... 152 CHAPTER 3: INTRA-OBSERVER RELIABILITY OF WAIST CIRCUMFERENCE MEASUREMENT ............................................................................................................. 153 3.1 Rationale for the intra-observer reliability study ................................................ 154 3.2 Objective ............................................................................................................. 154 3.3 Materials and methods ........................................................................................ 155 3.4 Statistical analysis ............................................................................................... 157 3.5 Results ................................................................................................................. 157 3.6 Discussion ........................................................................................................... 158 CHAPTER 4: RESULTS AND DISCUSSION ................................................................ 160 4.1 Study I ................................................................................................................. 160 4.1.1 Results ......................................................................................................... 160 4.1.2 Discussion .................................................................................................... 178 4.2 Study II ............................................................................................................... 197 4.2.1 Results ......................................................................................................... 197 4.2.2 Discussion .................................................................................................... 211 CHAPTER 5: GENERAL DISCUSSION AND CONCLUSION .................................... 227 5.1.1 Limitations ................................................................................................... 230 5.1.2 Directions for future research ...................................................................... 235 5.1.3 General Conclusion ..................................................................................... 237 CHAPTER 6: REFERENCES ........................................................................................... 241 CHAPTER 7: APPENDICES ............................................................................................ 302 iv Abstract Polyphenols are phytochemicals widely available in plants. Dark chocolate (DC) is a high source of polyphenols, particularly