No description available.

Previous studies have suggested that brief exposure to the sight and smell of food can elicit a momentary increase in desire to eat that food and can stimulate food intake. This thesis sought to explore individual differences in this 'food-cue reactivity.' Specifically, it aimed to explore associations between reactivity to food cues and i) dietary restraint (Experiments 1 to 6), ii) dietary disinhibition (Experiments 1 to 6), iii) everyday portion-size selection (Experiments 3 to 5), iv) body weight (Experiments 5 and 6), v) sensitivity to reward (BAS trait) (Experiment 6), and vi) Impulsivity (Experiment 6) Using a typical cue reactivity paradigm, female students (Experiment 1 n = 56, Experiment 2 n= 120, Experiment 3 n = 30, Experiment 4 n = 30, Experiment 5, n = 120, Experiment 6 n = 120) from Loughborough University (aged between 18 and 30) were exposed to a food cue and then a series of subjective (appetite ratings), and behavioural (intake and desired portion size), markers of appetite were assessed Notably, two main findings emerged from this research. Firstly, there was little evidence to suggest that food-cue reactivity shared any association with dietary restraint status per se. Rather, sensitivity to reward, impulsivity, and dietary disinhibition, were identified as potentially important determinants of sensitivity to food cues. Secondly, some experiments (Experiments 3 and 5) suggested that foodcue reactivity might be elevated in individuals who are overweight, and who select larger everyday portion sizes. Based on these findings, conclusions are drawn regarding the potential mechanisms which might govern food-cue reactivity, and the possible consequences of greater reactivity for everyday food consumption. In particular, it is concluded that food-cue reactivity might result from a universal sensitivity to stimuli which predict the occurrence of a reward, and from an inability to exercIse sufficient self-control in the presence of tempting environmental cues. In addition to this, it is also suggested that, over time, a greater susceptibility to the effects of food cues might contribute to, greater everyday food intake, and weight gain. To move forward within this research area, studies should continue to investigate the role of food-cue reactivity in overeating, and seek to further identify the mechanisms which promote greater reactivity to these cues.

Sexual selection and sexual conflict are two fundamental evolutionary mechanisms that are responsible for the diversification of a range of morphological, behavioural and physiological traits in the sexes, across most animal taxa. Decades of empirical research has shown that the expression of many (if not all) of these traits is dependent on diet. Few studies have, however, provided a detailed view of how diet influences the operation of sexual selection and sexual conflict. The traditional view that nutritional resources are of a single form, namely energy or calories, has recently been challenged by the idea that it is the combination of various micro- and/or macronutrients that is key to trait expression and in maintaining reproductive fitness. While this established dogma is changing, more empirical studies are needed that focus on the how the intake of specific nutrients influence the expression of key traits that regulate the operation of sexual selection and sexual conflict. In this thesis I examine the role of nutrition on the operation of sexual selection and sexual conflict. To achieve this I perform a number of experiments utilising the Geometric Framework (GF) of nutrition to tease apart specific effects of two macronutrients (protein and carbohydrates) on a number of important phenotypic traits in two field cricket species; the decorated cricket Gryllodes sigillatus and the Australian black field cricket Teleogryllus commodus. I also combine the GF with conventional quantitative genetic experiments to examine the potential for the genetics of dietary choice to constrain the evolution of key traits that regulate sexual selection and sexual conflict. I start by examining the effect of protein (P) and carbohydrate (C) intake on a male sexual trait, the cuticular hydrocarbon (CHC) profile, known to be subject to strong pre-copulatory sexual selection in G. sigillatus. I find that diet influences the expression of male CHCs and how attractive a male is to a female. Specifically, I show that CHCs are maximized at a high intake of nutrients in a P:C ratio of 1:1.5, that female pre-copulatory choice exerts significant selection on this variation in male CHCs and that the nutritional optima for male mating success almost perfectly matched the optima for CHC expression. However, this change in CHC expression was not the only pathway for the effects of nutrient intake on male pre-copulatory attractiveness to females suggesting that other trait(s) are also important in mediating this relationship (Chapter 2). Next, I examine the effect of the intake of these nutrients on the regulation of sexual conflict in G. sigillatus. Males in this species produce a large, gelatinous nuptial gift (the spermatophylax) that the female consumes during mating and that prevents her from prematurely removing the sperm-containing ampulla and terminating mating. The size and amino acid composition of the spermatophylax are known to prolong the attachment time of the ampulla and, therefore, prevent the female from exerting post-copulatory mate choice. I show that the size and amino acid composition that increases the gustatory appeal of the spermatophylax to females is maximised at a high intake of nutrients in a P:C ratio of 1:1.3 (Chapter 3). Furthermore, I show that the nutritional optima for these properties of the spermatophylax are almost perfectly aligned with the optima for ampulla attachment time. This suggests that the balanced intake of P and C is fundamental to the regulation of sexual conflict in this species. A key assumption in life-history theory is that phenotypic traits important to fitness will be subject to trade-offs as they compete for a limited pool of resources. In most empirical studies, the nutrients in food are considered the resource that life-history traits compete for during development, yet the diets provided are typically poorly resolved so that the specific nutrients regulating any trade-off cannot be determined. While the GF provides a powerful way to examine how specific nutrients influence the trade-off between traits, this framework currently lacks a robust protocol to quantify the presence and magnitude of nutritionally based trade-offs. In Chapter 4, I start by developing a standardized protocol for quantifying the presence and magnitude of nutritionally based trade-offs when using the GF. This work shows that nutritionally based trade-offs occur when life-history traits are maximised in different regions of nutrient space and that this divergence can be quantified by the overlap in the 95% confidence region (CR) of the global maxima, the angle (θ) between the linear nutritional vectors and the Euclidean distance (d) between the global maxima for each trait. As these metrics are measured in a standardized way, they can be directly compared across different traits, the sexes and model organisms. Next, I test this protocol by examining the nutritional basis of the trade-off between reproductive effort and immune function in male and female G. sigillatus. I show that encapsulation ability and egg production in females increased with the intake of both nutrients, being maximised at a P:C ratio of 1.04:1 and 1:1.17, respectively. In contrast, encapsulation ability in males only increased with the intake of P being maximised at a P:C ratio of 5.14:1, whereas calling effort increased with the intake of C but decreased with the intake of P and was maximized at a P:C ratio of 1:7.08. Consequently, the trade-off between reproduction and encapsulation ability is much larger in males than females and this is supported by the non-overlapping 95% CRs on the global maxima for these traits in males and the larger estimates of θ and d. Sexual selection promotes the evolution of sex differences in life history strategies and this often requires different intakes of nutrients. Indeed, the sexes in many different species have evolved divergent nutritional optima for a range of important fitness-related traits. If dietary choice for the intake of these nutrients is genetically uncoupled in the sexes, males and females should evolve sex differences in nutrient intake and each sex should evolve to their sex-specific nutritional optima. However, if the sexes have different nutritional optima but dietary choice is positively genetically correlated between the sexes, this will constrain the evolution of sexual dimorphism in nutrient intake and prevent one or both sexes from reaching their nutritional optima: a process known as intralocus sexual conflict (ISC). In Chapter 5, I examine the potential for ISC over the optimal intake of nutrients for reproduction and lifespan in male and female black field crickets, T. commodus. I show that males and females have distinct dietary optima for lifespan and reproductive effort. Male lifespan and nightly calling effort were both maximised at a high intake of nutrients in a P:C ratio of 1:8, whereas female lifespan and daily egg production were maximised at a high intake of nutrients in a P:C ratio of 1:2 and 1:1, respectively. Using a half-sib quantitative genetic breeding design I also showed positive genetic correlations between the intake of P and C in the sexes. Together this provides the potential for ISC over the optimal intake of nutrients to influence the evolution of sexual dimorphism in reproductive effort and lifespan. However, by measuring the genetic constraint (which compares the predicted evolutionary response of these traits when there is genetic covariance between the sexes for nutrient intake, to the predicted response when the genetic covariance is set to zero (i.e. no genetic constraint)), I show that the positive genetic correlations over nutrient intake had little effect on the predicted response of nutrient regulation in the sexes. / My work challenges the longstanding view that calories and/or energy content are the main drivers of costly sexual traits and sexually dimorphic life-history strategies and shows that a balanced intake of specific nutrients (namely P and C) plays a far more important role. My work also highlights that the genetics of dietary choice can also have important consequences for how important life-history traits, such a lifespan and reproductive effort, are able to evolve independently in the sexes and the implications this has for the regulation of nutrients and the potential risks to health when consuming an imbalanced diet.

Intermittent fasting describes dietary strategies in which the pattern of energy restriction (intermittent energy restriction, IER) or timing of food intake (time-restricted feeding, TRF) are altered such that individuals undergo repeated periods of “fasting”. The overarching aim of this PhD project was to investigate the metabolic health impacts of these intermittent fasting variants. Intermittent energy restriction: Study one assessed the acute metabolic effects of substantial energy restriction (ER) in healthy, overweight/obese participants using a cross-over design. Six-hour postprandial responses were assessed the morning following one day of total 100% ER, partial 75% ER and isoenergetic intake (0% ER) via serial blood sampling and indirect calorimetry. Postprandial substrate oxidation was shifted towards fat oxidation (p = 0.080) and ketogenesis (p < 0.001) in an apparent dose response manner following 75-100% ER, translating to a reduction in postprandial lipaemia (p < 0.001). Conversely, glucose tolerance was impaired (p = 0.002). Study two utilised similar methods to investigate the chronic effect of IER (75% ER for two days/week) on postprandial metabolism following 5% weight-loss. This was compared to matched weight-loss achieved via a “standard treatment” control of continuous ER (2510kJ/day deficit). Rates of weight-loss were similar between groups (p = 0.446), despite greater reported reductions in energy intake during IER (p = 0.012), which might be explained in part by an adaptive decline in resting energy expenditure (p = 0.067). Both interventions comparatively (p = 0.903) improved postprandial insulinaemia, whereas the relative reduction in postprandial lipaemia was greater following IER (p = 0.042). Time-restricted feeding: Study three examined the effects of a 10-week, three-hour daily shortening of the eating window on fasting metabolism and adiposity utilising a parallel-armed controlled design. In a small group of lean and overweight/obese participants, TRF led to modest reductions in adiposity (p = 0.047) and fasting glycaemia (p = 0.073), possibly explained by the spontaneous reduction in energy intake observed. Combined, these data provide novel insights into the metabolic effects of intermittent fasting. Replication and mechanistic evaluation in diverse population groups, including those with established metabolic disorders, is warranted.

Dietary supplementation with inorganic nitrate has been shown to lower the oxygen cost of submaximal exercise and to improve performance during continuous endurance exercise. The objectives of this thesis were: 1) to improve understanding of the supplementation procedures in which nitrate is most likely to benefit exercise physiology and performance, and 2) to explore the ergogenic potential of dietary nitrate in intermittent exercise. Recreationally-active adult participants volunteered to participate in the original investigations presented in this thesis. These participants underwent various oral nitrate supplementation regimes and subsequently provided venous blood samples for the determination of plasma nitrate concentration and plasma nitrite concentration, and completed different exercise tests to assess the potential for nitrate supplementation to improve physiological responses during exercise and exercise performance. Chapter 4: Following the ingestion of 70, 140 and 280 mL concentrated nitrate-rich beetroot juice (containing 4.2, 8.4 and 16.8 mmol nitrate, respectively) plasma nitrite concentration increased dose-dependently, with peak changes occurring at ~2-3 h post ingestion. The oxygen cost of submaximal exercise and exercise tolerance were also influenced dose-dependently 2.5 h post acute BR ingestion when compared to a nitrate-depleted placebo. Specifically, 8.4 mmol and 16.8 mmol lowered the oxygen cost of moderate-intensity exercise by 1.7% (P = 0.06) and 3.0% (P < 0.05), respectively. Exercise tolerance during severe-intensity exercise was significantly improved after ingestion of 8.4 mmol (+14%; P < 0.05), with no further improvement evident following ingestion of 16.8 mmol (+12%; P < 0.05). 4.2 mmol nitrate did not significantly lower the oxygen cost of submaximal exercise or improve exercise tolerance. Chapter 5: Plasma nitrite concentration was dose-dependently elevated 2 h and after 7 days and ~4 weeks of supplementation with 3 mmol and 6 mmol nitrate. Compared to pre-supplementation baseline, and placebo, moderate-intensity exercise oxygen uptake was not lowered with 3 mmol nitrate acutely (2 h) or after ingesting it daily up to ~4 weeks. In contrast, ingestion of 6 mmol nitrate significantly lowered submaximal exercise oxygen uptake by 3% after 2 h (P = 0.06), 7 days and ~4 weeks (both P < 0.05) of supplementation. Another interesting observation was that the reduction in submaximal exercise oxygen uptake after ~4 weeks of supplementation with 6 mmol nitrate was preserved 24 h after consumption of the final nitrate dose despite plasma nitrite concentration having returned to baseline. Chapter 6: In recreational team sport players, 28 mmol dietary nitrate administered over ~30 h improved performance in the Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) test (a test that mimics the high-intensity intermittent exercise bouts typical of team sport games) by 4.2%, compared to placebo (nitrate: 1704 m vs. placebo: 1636 m). The decline (or ‘utilisation’) of plasma nitrite from pre-exercise to post-exercise was greater with BR compared to placebo, and the magnitude of this decline in plasma nitrite was positively correlated with the improvement in Yo-Yo IR1 performance. Chapter 7: Supplementation with dietary nitrate for 3-5 days (8.2 mmol nitrate per day) significantly improved performance during 24 x 6-s all-out cycling sprints interspersed with 24 s recovery, but not during 7 x 30-s all-out sprints interspersed with 240 s of recovery or 6 x 60-s self-paced maximal efforts interspersed with 60 s of recovery, in a group of recreational team sport players. The novel findings presented in this thesis suggest that the supplementation procedure, in particular the nitrate dose administered, should be carefully considered by individuals wishing to elicit ergogenic effects following dietary nitrate supplementation. Specifically, the findings suggest that a low dose (≤4.2 mmol) of nitrate is not sufficient to acutely improve exercise tolerance, and that submaximal exercise oxygen uptake is not lowered following acute or prolonged (~30 day) supplementation with a low nitrate dose. In contrast, results show that higher doses (6-8.4 mmol) of nitrate might be sufficient to acutely lower the oxygen cost of submaximal exercise and improve exercise tolerance. The present thesis also provides evidence to indicate that dietary nitrate might hold potential as an ergogenic aid for individuals participating in intermittent exercise involving brief bouts of high-intensity exercise interspersed with short recovery periods, such as team sport players. These findings are of importance as they will help inform supplementation procedures in future studies assessing the ergogenic efficacy of nitrate supplementation. Moreover, they suggest that nitrate supplementation has the potential to improve performance during intermittent exercise as well as continuous endurance exercise.

Background: Food composition data, front-of-pack nutrition labelling and nutrition and health claims have an important role to play in the development of appropriate policy, regulation and public health interventions ultimately aimed at reducing the burden of diet-related chronic disease. The overarching aim of this thesis is to explore whether the communication of healthier food choice through front-of-pack (FOP) nutrition labelling and health claims can be enhanced by the development of consumer derived frameworks (typologies) of these domains, a greater understanding of the degree to which the different FOP labelling schemes impact on consumer health inferences and an improved approach to the sharing of food composition data between stakeholders. Method: The potential for more effective approaches to the transfer of food composition data on processed foods, was explored via a survey conducted within the UK food industry (Study 1). To facilitate the development of a consumer derived typology of FOP nutrition labelling schemes in Europe, a free-sorting study utilising the ‘Multiple Sort Procedure’ (MSP) was performed in four countries; France, Poland, Turkey and the United Kingdom (Study 2). Building on the MSP methodology utilised in Study 2, a further study on nutrition and health claims was performed in five countries; Germany, the Netherlands, Slovenia, Spain and the United Kingdom. (Study 3). The final study in this thesis sought to quantify the extent to which consumer perceptions of healthiness are impacted by the interpretative elements of the prevalent FOP labelling schemes in four countries; Germany, Poland, Turkey and the United Kingdom (Study 4). Conclusion: The outcomes of this research propose an optimised approach to the sharing of food composition data, an optimised approach to FOP labelling and consumer derived typologies for both the FOP labelling and nutrition and health claims domains.

No description available.

No description available.

Coffee is a rich source of caffeoylquinic acids, esters of caffeic or ferulic acid and quinic acid and its consumption is associated with various health benefits. However, upon ingestion of coffee, caffeoylquinic acids are abundantly absorbed, widely metabolised and extensively excreted in humans. The first part of this thesis addresses the synthesis and subsequent analysis of several glycine conjugates of hydroxycinnamic acid in urine collected by six participants of a pilot human study. For the first time vanilloylglycine has been quantified in urine for the first time after coffee consumption in similar amounts to feruloylglycine, whereas 3,4-dimethoxycinnamoylglycine, 3,4-dimethoxydihydrocinnamoylglycine, 3,4-dimethoxybenzoylglycine and dihydroferuloylglycine have only been detected in trace amounts. The second part of this thesis describes the chemical synthesis of several hundred milligrams of dihydrocaffeic acid-3-O-sulfate, ferulic acid-4-O-sulfate, and dihydroferulic acid-4-O-sulfate, the development of a rapid LC-MS method for the analysis of the five most excreted urinary metabolites of caffeoylquinic acids, the design and performance of a human study investigating the intra- and interindividual absorption of caffeoylquinic acids in humans and linking these results to biomarkers of health and food intake. Among 62 participants, an 8-fold variation in excretion of the total amount of the five most abundant, urinary metabolites excreted over 36 hours after coffee consumption was calculated and the intraindividual variation between repeated visits was the highest for colonic metabolites. A moderate, negative correlation of the absorption of caffeoylquinic acids with the weekly consumption of coffee was established. The data suggests a strong impact of colonic catabolism on the absorption and metabolism of caffeoylquinic acids and a reducing effect of heavy coffee consumption on the absorption of caffeoylquinic acids in humans.

Evidence suggests that the workplace is a potentially effective setting for interventions to reach a large number of people from different professions and socio-demographic backgrounds and promote dietary behaviour change. As businesses are likely to benefit from healthier staff, employers are recognising the potential that supporting staff in leading healthier lifestyles may have and are becoming increasingly supportive of workplace wellbeing programmes. However, most evidence on behaviour change in the workplace comes from interventions addressing multiple health behaviours, making it difficult to draw conclusions on effective diet-related strategies. The main focus of this thesis has been to evaluate the effectiveness of nutrition workplace interventions on diet-, health- and work-related outcome measures; to identify demographic characteristics that may influence food choice in working populations; and the barriers and motivators of catering establishments to provide healthier food options.