Benzodiazepine receptors and the control of ingestive behaviour in the rat

When administered systemically, benzodiazepine receptor agonists have been shown to increase food intake in a number of species. Conversely, benzodiazepine receptor inverse agonists bring about reliable decreases in feeding. The aim of the experiments reported in this thesis was to investigate the brain and behavioural mechanisms involved in the effects of benzodiazepines on ingestion. The effect on food intake of microinjection of the benzodiazepine receptor agonist midazolam into the brainstem of the rat was investigated. A reliable hyperphagic response was elicited following injection of midazolam into both the IVth ventricle and the parabrachial nucleus (PEN). This increase in intake was reversed by pretreatment with the selective benzodiazepine receptor antagonist flumazenil. These results suggest that benzodiazepine receptors located in the brainstem, specifically in the PEN, may be responsible for the effects of benzodiazepines on ingestion. In further experiments, a microstructural approach was adopted which involved analyzing the effects of benzodiazepine ligands on the detailed pattern of licking for both a carbohydrate and a fat in the rat. The effects of midazolam were similar to the effects of increasing concentration. The effects of the benzodiazepine receptor inverse agonist Ro 15-4513 were similar to the effects of decreasing concentration. These results suggest that benzodiazepines influence ingestive behaviour by modulating palatability. The proposal that benzodiazepines may interact with opioids to influence feeding behaviour was examined in Chapters 7 and 8. Although the effects of the opioid agonist morphine and the opioid antagonist naloxone on licking behaviour were not the same as the effects of benzodiazepine ligands, naloxone blocked the effects of midazolam. These results suggest that the effects of benzodiazepine on palatability may depend on release of endogenous opioid peptides. This work has implications for understanding the neural control of ingestive behaviour and may help in developing new therapies for clinical disorders such as anorexia and bulimia

Social influences on eating

Eating behaviour is strongly influenced by social context. We eat differently when we are with other people compared with when we eat alone. Our dietary choices also tend to converge with those of our close social connections. One reason for this is that conforming to the behaviour of others is adaptive and we find it rewarding. Norms of appropriate eating are set by the behaviour of other people, but also shared cultural expectations and environmental cues. We are more likely to follow an eating norm if it is perceived to be relevant based on social comparison. Relevant norms are set by similar others and those with whom we identify. If a norm is relevant then there may be matching of behaviour to the norm, but this will depend on other factors, such as how much attention is paid to the norm, how concerned we are about social acceptance and the presence of other competing norms such as personal norms and consumption stereotypes. Norm matching involves processes such as synchronisation of eating actions, consumption monitoring and altered food preferences. There is emerging evidence that social eating norms may play a role in the development and maintenance of obesity. Social eating norms constitute a novel target for interventions to encourage healthier eating

The role of irrational beliefs in the relationship between attention deficit hyperactivity disorder (ADHD) symptoms and disordered eating in two general student samples

Attention deficit hyperactivity disorder (ADHD) symptoms are associated with disordered eating and negative mood. The purpose of this study was to examine whether irrational beliefs mediate this relationship along with previously reported mediators such as depression and impulsivity. Irrational beliefs trigger negative automatic thoughts which are believed, in cognitive behavior therapies, to be a source of psychopathology. Challenges brought about by symptoms of ADHD may lead to habitual emotion-eliciting thought patterns which, in turn, could lead to negative mood and disordered eating. Undergraduate students (N = 127) completed online questionnaires assessing ADHD symptoms and disordered eating and several potential mediators including irrational beliefs, depression, impulsivity, interoceptive accuracy, and reward responsiveness. The results, which were replicated in a second study (N = 254), indicated that irrational beliefs and depression mediated the relationship between ADHD symptoms and disordered eating. In the second study, impulsivity due to negative urgency was also a mediator. These findings support the theory that the symptoms of ADHD lead to enhancement of irrational beliefs, depression, and negative urgency which are linked to disordered eating.</p

Social influences on eating: implications for nutritional interventions

We review recent research on the effect of social context on food intake and food choice and assess the implications for nutritional interventions. We focus on studies of modelling of eating behaviour and the impact of perceived eating norms on the amounts and types of food that individuals eat. We suggest that social context influences eating via multiple mechanisms, including identity signalling and self-presentation concerns. However, building on existing theoretical models, we propose that social factors may be particularly influential on nutrition because following the behaviour of others is adaptive and social norms inform individuals about behaviours that are likely to be optimal (‘if everyone else is doing it, I probably should be’). Guided by understanding of the potential underlying mechanisms, we discuss how social norms might be used to promote healthier nutrition

Cognitive processing of food rewards

AbstractCues associated with tasty foods, such as their smell or taste, are strong motivators of eating, but the power of food cues on behaviour varies from moment to moment and from person to person. Variation in the rewarding value of a food with metabolic state explains why food cues are more attractive when hungry. However, cognitive processes are also important determinants of our responses to food cues. An urge to consume a tempting food may be resisted if, for example, a person has a longer term goal of weight loss. There is also evidence that responses to food cues can be facilitated or inhibited by memory processes. The aim of this review is to add to the literature on cognitive control of eating by reviewing recent evidence on the influence of working memory and episodic memory processes on responses to food cues. It is argued that processing of food information in working memory affects how much attention is paid to food cues in the environment and promotes the motivation to seek out food in the absence of direct contact with food cues. It is further argued that memories of specific recent eating episodes play an important role in directing food choices and influencing when and how much we eat. However, these memory processes are prone to disruption. When this happens, eating behaviour may become more cue-driven and less flexible. In the modern food environment, disruption of cognitive processing of food reward cues may lead to overconsumption and obesity

Self-control mediates the relationship between time perspective and BMI

Trait future time perspective measures the extent to which behaviour is dominated by a striving for future goals and rewards. Trait present time perspective measures orientation towards immediate pleasure. Previous research has explored the relationship between future and present time perspective and BMI with mixed findings. In addition, the psychological mechanism underlying this relationship is unclear. Self-control is a likely candidate, as it has been related to both BMI and time perspective, but the relationship between all of these concepts has not been examined in a single study. Therefore, the aim of this study was to examine if trait self-control mediates the relationship between time perspective (future and present) and BMI. Self-report time perspective (ZTPI), self-control (SCS) and height/weight data were collected using an online survey from a mixed student and community sample (N=218) with wide ranging age (mean 29, SD 11, range 18-73 years) and BMI (mean 24, SD 4, range 15-43). The results of a structural equation model including both facets of time perspective suggested that the traits are related yet distinct measures that independently predict BMI through changes in self-control. Bootstrap mediation analysis showed that self-control mediated the relationship between both future time perspective (95% CI, -.10 to -.02) and present time perspective (95% CI, .03 to .17), and BMI in opposite directions. Participants with higher future time perspective scores (higher present time perspective scores) had higher (lower) self-control, which predicted lower (higher) BMI. These results are consistent with previous research suggesting an important role for time perspective in health outcomes. Self-control likely mediates the relationship between temporal perspectives and BMI, suggesting that time perspective may be a target for individualised interventions