Psychological determinants and consequences of self-perceived food addiction

Introduction: Many people believe that obesity is caused by an addiction to food. However, within the scientific community, there is ongoing debate surrounding the validity of the food addiction concept, and an operational definition of food addiction is yet to be established. An aim of the current thesis was to identify behaviours and cognitions which characterise addictive patterns of eating. To do so, Chapters 2-4 explored the characteristics of individuals who perceive themselves to be addicted to food (i.e. self-perceived food addicts). Based on these findings, Chapter 5 presents the development of a novel assessment tool for addictive-like eating. A second aim of the thesis was to explore food addiction beliefs from a psychosocial perspective. Specifically, Chapter 6 examined the consequences of food addiction beliefs on subsequent eating, and Chapter 7 explored whether the concept of food addiction may be used to alleviate eating-related guilt by implying that eating is beyond personal control. Methods: A combination of qualitative and experimental techniques were used to establish the cognitive and behavioural features of self- perceived food addiction. Chapter 2 consisted of a brief questionnaire which inductively explored beliefs about the manifestations of food addiction within the lay public. These findings were extended in Chapters 3 and 4 which experimentally tested whether self-perceived food addicts would demonstrate increased food reward and attention to high-fat food cues (using an eye-tracking paradigm), compared to those who do not perceive themselves as food addicts. Chapter 5 used exploratory and confirmatory factor analyses to develop a novel tool for the assessment of addictive eating (i.e. the Addictive Eating Behaviour Scale, AEBS). To address the second aim of the thesis, experimental techniques were used to manipulate participants’ beliefs about their levels of food addiction (Chapter 6) and feelings of eating-related guilt (Chapter 7). The effects of these beliefs on subsequent food intake (Chapter 6) and food addiction attributions (Chapter 7) were then examined. Results: Findings from Chapter 2 suggested that self-perceived food addicts find food particularly rewarding and may be particularly likely to overeat. Consistent with these findings, Chapter 3 found that self-perceived food addicts demonstrated increased desire-to-eat for a range of food, and consumed more of a high-fat food during ad libitum access, compared to self-perceived non-addicts. However, self- perceived food addicts did not show any increased attentional bias to food cues compared to non-addicts (Chapter 4). The AEBS (Chapter 5) consisted of two sub- scales: 1) unhealthy eating/low self-control, and 2) overeating/weight gain. This scale predicted variance in BMI beyond that accounted for by an existing measure of food addiction. With regard to the second aim of the thesis, Chapter 6 found that those who were told they had high levels of ‘food addiction’ consumed fewer calories compared to those who were told they had ‘low’ or ‘average’ food addiction. This was mediated by increased dietary concern and a reduction in the amount of time spent tasting high-fat foods. Finally, Chapter 7 found no effect of manipulating eating-related guilt on food addiction beliefs; however, across the whole sample, higher levels of guilt correlated with an increased tendency to attribute eating to the foods’ addictiveness. Conclusions:Overall, these findings suggest that self-perceived food addiction is characterised by several core behaviours, and that perceiving oneself to be a food addict may be helpful for those attempting to reduce their intake of certain foods, in the short-term at least. Future research should establish whether the AEBS captures food reward and calorie intake beyond that accounted for by established measures of aberrant dietary behaviour. Research should also examine the effects of food addiction beliefs on longer-term patterns of eating

A laboratory study of high-performance cold mix asphalt mixtures reinforced with natural and synthetic fibres

This research aims to examine the impact of using natural and synthetic fibres as reinforcing materials, on the mechanical properties and water susceptibility of cold mix asphalt (CMA) including indirect tensile stiffness and resistance to rutting, cracking and moisture damage. Four different types of fibres were used: glass as a synthetic fibre, and hemp, jute and coir as natural fibres. Various samples of CMA, with and without fibres, were fabricated and tested. Traditional hot mix asphalt (HMA) was also used for comparison. The results indi cate a significant improvement in the indirect tensile stiffness modulus, for all fibre-reinforced CMA mixtures, over different curing times. The improved tensile behaviour represents a substantial contribution towards slowing crack propagation in bituminous mixtures, while scanning electron microscopy analysis confirmed the fibre shape and surface roughness characteristics. The improved performance of the reinforced mixtures with both natural and synthetic fibres, facilitated a substantially lower permanent deformation than traditional hot and cold mixtures at two different temperatures (45 °C and 60 °C). When using glass and hemp fibres as reinforcing materials, there was a significant improvement in CMA in terms of water sensitivity. Resistance to surface cracking was also improved when fibres were incorporated. Based on the test results, 0.35% fibre content by mass of dry aggregate and 14 mm fibre length are recommended to achieve the optimum performance output for indirect tensile stiffness. © 2018 Elsevier Lt

Predicting the rutting behaviour of natural fibre-reinforced cold mix asphalt using the finite element method

This paper describes the development of a three-dimensional (3-D), finite element model (FEM) of flexible pavements made with cold mix asphalt (CMA), which has itself been reinforced with two different natural fibres: jute and coir. A 3-D finite element model was employed to predict the viscoelastic response of flexible CMA pavements when subjected to multiple axle loads, different bituminous material properties, tire speeds and temperatures. The analysis was conducted by the finite element computer package ABAQUS/STANDARD. The pavements were subject to cyclic and static loading conditions to test for permanent deformation (rutting). The accuracy of the developed model was validated by comparing the predicted results with those measured in the lab. Reinforced and unreinforced CMA mixture models were simulated in this research. The results indicate that the CMA mixtures reinforced with natural fibres, are effective in mitigating permanent deformation (rutting). These reinforcing materials can extend the service life of flexible pavements. © 2018 Elsevier Lt

A viscoplastic model for permanent deformation prediction of reinforced cold mix asphalt

A reliable viscoplastic model of natural and synthetic fibres reinforced cold bitumen emulsion mixture is developed and applied to characterize the rutting behaviour of asphalt pavement by using finite element analysis. It is indicated that the traffic load parameters such as temperature, static loading condition and vehicular speed not only affects the rutting depth, it accelerates the rutting rate, causing the pavement earlier enter into rutting failure with shortened service life. Several finite element models (FEM) have been developed to simulate the behaviour of hot mix asphalts (HMAs), but none exists for cold mix asphalt (CMA) reinforced by natural and synthetic fibres. This research presents the first three dimension (3-D), finite element model (FEM) to assess the viscoplastic behaviour of reinforced CMA mixtures. The model is also able to predict rutting (permanent deformation) of asphalt mixtures under different traffic and environmental loadings, traditional HMA used as a comparison. The enhancement of the performance of CMA mixtures against permanent deformation using finite element software (ABAQUS) was validated by comparing the models’ predictions with measurements from wheel-tracking tests at different temperatures (45 °C and 60 °C). A very good level of agreement was found between the rutting predicted by the model and the experimental test. The results show that the finite element model can successfully predict rutting of flexible pavements under different temperatures and wheel loading conditions. Finally, the natural and synthetic fibres reinforced CMA mixtures are much more effective at resisting permanent deformation damage than conventional cold and hot asphalt mixtures. © 2018 Elsevier Lt

Impact of New Method for Laying Separate Sewer System on Pavement Layers

The method of installing underground infrastructure has a significant influence on road resistance and performance under live loads such as traffic. This research presents a new method for laying separate sewer systems by using one trench to sit both sanitary pipe and storm pipe and considers the effects of this approach on the pavement strength. Experimental tests have been conducted in the laboratory using a trench 2.5x0.45x1 metre to install two pipes one over the other (sanitary pipe in the bottom and storm pipe on top). Two cases have tested, the first case using 5 cm surface layer of cold mix asphalt while the second is using soil. A series of loads were applied to test the behaviour of this new system and its effects on the pavement surface layer and the buried pipe. The comparison between the rut print of the live load on the soil layer and the pavement layer was conducted. Results demonstrated that using the cold mix asphalt is still insufficient to provide enough safety to protect buried pipe as a reason of needing to relatively long time to acquire high stiffness. Therefore, minimum cover depth to protect pipelines still required

The development and validation of the Addiction-like Eating Behaviour Scale

Background: Overeating and obesity are frequently attributed to an addiction to food. However, there is currently a lack of evidence to support the idea that certain foods contain any specific addictive substance. An alternative approach is to focus on dimensions of observable behaviour, which may underpin a behavioural addiction to eating. To facilitate this, it is necessary to develop a tool to quantify addiction-like eating behaviour, which is not based on the clinical criteria for substance dependence. The current study provides initial validation of the Addiction-like Eating Behaviour Scale (AEBS). Methods: English speaking male and female participants (N=511) from a community sample completed the AEBS, alongside a range of other health- and eating-related questionnaires including the Yale Food Addiction Scale (YFAS) and Binge Eating Scale (BES). Participants also provided their height and weight to enable calculation of body mass index (BMI). Finally, to assess test–retest reliability, an additional 70 participants completed the AEBS twice, 2 weeks apart. Results: Principle components analysis revealed that a two-factor structure best accounted for the data. Factor 1 consisted of items that referred to appetitive drive, whereas factor two consisted of items that referred to dietary control practices. Both subscales demonstrated good internal reliability and test–retest reliability, and a confirmatory factor analysis confirmed the two-factor scale structure. AEBS scores correlated positively with body mass index (BMI) (P<0.001) and other self-report measures of overeating. Importantly, the AEBS significantly predicted variance in BMI above that accounted for by both the YFAS and BES (P=0.027). Conclusions: The AEBS provides a valid and reliable tool to quantify the behavioural features of a potential ‘eating addiction’. In doing so, the AEBS overcomes many limitations associated with applying substance-dependence criteria to eating

High Density Lipoprotein (HDL) Promotes Glucose Uptake in Adipocytes and Glycogen Synthesis in Muscle Cells

Background: High density lipoprotein (HDL) was reported to decrease plasma glucose and promote insulin secretion in type 2 diabetes patients. This investigation was designed to determine the effects and mechanisms of HDL on glucose uptake in adipocytes and glycogen synthesis in muscle cells. Methods and Results: Actions of HDL on glucose uptake and GLUT4 translocation were assessed with 1- [ 3 H]-2deoxyglucose and plasma membrane lawn, respectively, in 3T3-L1 adipocytes. Glycogen analysis was performed with amyloglucosidase and glucose oxidase-peroxidase methods in normal and palmitate-treated L6 cells. Small interfering RNA was used to observe role of scavenger receptor type I (SR-BI) in glucose uptake of HDL. Corresponding signaling molecules were detected by immunoblotting. HDL stimulated glucose uptake in a time- and concentration-dependent manner in 3T3-L1 adipocytes. GLUT4 translocation was significantly increased by HDL. Glycogen deposition got enhanced in L6 muscle cells paralleling with elevated glycogen synthase kinase3 (GSK3) phosphorylation. Meanwhile, increased phosphorylations of Akt-Ser473 and AMP activated protein kinase (AMPK) a were detected in 3T3-L1 adipocytes. Glucose uptake and Akt-Ser473 activation but not AMPK-a were diminished in SR-BI knock-down 3T3-L1 cells. Conclusions: HDL stimulates glucose uptake in 3T3-L1 adipocytes through enhancing GLUT4 translocation by mechanisms involving PI3K/Akt via SR-BI and AMPK signaling pathways, and increases glycogen deposition in L6 muscle cells throug