Physiological regulation through learnt control of appetites by contingencies among signals from external and internal environments

Tasting More Than Just Food: Effect of Aesthetic Appeal of Plate Patterns on Food Perception

Interest has been growing in the role of subjective aesthetics in the field of food. This study explored the mechanisms by which the aesthetic appeal of plate patterns influences consumers’ perceptions of food. Three experiments were conducted to compare whether different levels of beauty and types of plate pattern aesthetics (classical versus expressive) affected the perceptions of tastiness and healthiness of the food offered. Experiment 1 was carried out with 30 participants, and the results showed that participants perceived the food presented on more beautiful plates as tastier and healthier than the food on less beautiful plates. Experiment 2 was carried out with 128 participants; the results showed that, for expressively aesthetic plates, the participants experienced more positive emotions for very beautiful plates and more negative emotions for less beautiful plates. However, for classical aesthetic plates, participants’ emotions were not affected by the beauty of the plate. Experiment 3 was carried out with 149 participants, and the results showed that, for classically aesthetic plates, participants perceived the food placed in the middle to be tastier than food placed at the edge; however, for expressively aesthetic plates, food placement did not affect participants’ perceptions of food. These results demonstrate the importance of the subjective beauty of plate patterns in influencing consumers’ food perceptions, although this influence varies depending on the type of aesthetic design of the plate pattern.

Control-theory models of body-weight regulation and body-weight-regulatory appetite

Human body weight (BW), or some variable related to it, is physiologically regulated. That is, negative feedback from changes in BW elicits compensatory influences on appetite, which may be called BW-regulatory appetite, and a component of energy expenditure (EE) called adaptive thermogenesis (AdEE). BW-regulatory appetite is of general significance because it appears to be related to a variety of aspects of human appetite beyond just energy intake. BW regulation, BW-regulatory appetite and AdEE are frequently discussed using concepts derived from control theory, which is the mathematical description of dynamic systems involving negative feedback. The aim of this review is to critically assess these discussions. Two general types of negative-feedback control have been invoked to describe BW regulation, set-point control and simple negative-feedback control, often called settling-point control in the BW literature. The distinguishing feature of set-point systems is the existence of an externally controlled target level of regulation, the set point. The performance of almost any negative-feedback regulatory system, however, can be modeled on the basis of feedback gain without including a set point. In both set-point and simple negative-feedback models of BW regulation, the precision of regulation is usually determined mainly by feedback gain, which refers to the transformations of feedback into compensatory changes in BW-regulatory appetite and AdEE. Stable BW most probably represents equilibria shaped by feedback gain and tonic open-loop challenges, especially obesogenic environments. Data indicate that simple negative-feedback control accurately models human BW regulation and that the set-point concept is superfluous unless its neuroendocrine representation is found in the brain. Additional research aimed at testing control-theory models in humans and non-human animals is warranted.

Resilience in farm animals: biology, management, breeding and implications for animal welfare

A capacity for the animal to recover quickly from the impact of physical and social stressors and disease challenges is likely to improve evolutionary fitness of wild species and welfare and performance of farm animals. Salience and valence of stimuli sensed through neurosensors, chemosensors and immunosensors are perceived and integrated centrally to generate emotions and engage physiological, behavioural, immune, cognitive and morphological responses that defend against noxious challenges. These responses can be refined through experience to provide anticipatory and learned reactions at lower cost than innate less-specific reactions. Influences of behaviour type, coping style, and affective state and the relationships between immune responsiveness, disease resistance and resilience are reviewed. We define resilience as the capacity of animals to cope with short-term perturbations in their environment and return rapidly to their pre-challenge status. It is manifested in response to episodic, sporadic or situation-specific attributes of the environment and can be optimised via facultative learning by the individual. It is a comparative measure of differences between individuals in the outcomes that follow exposure to potentially adverse situations. In contrast, robustness is the capacity to maintain productivity in a wide range of environments without compromising reproduction, health and wellbeing. Robustness is manifested in response to persistent or cyclical attributes of the environment and is effected via activity of innate regulatory pathways. We suggest that for farm animals, husbandry practices that incorporate physical and social stressors and interactions with humans such as weaning, change of housing, and introduction to the milking parlour can be used to characterise resilience phenotypes. In these settings, resilience is likely to be more readily identified through the rate of return of variables to pre-challenge or normal status rather than through measuring the activity of diverse stress response and adaptation mechanisms. Our strategy for phenotyping resilience of sheep and cattle during weaning is described. Opportunities are examined to increase resilience through genetic selection and through improved management practices that provide emotional and cognitive enrichment and stress inoculation.

Eating 'attentively' reduces later energy consumption in overweight and obese females

Attentional and memory processes underpin appetite control, but whether encouraging overweight individuals to eat more 'attentively' can promote reductions in energy consumption is unclear. In the present study with a between-subjects design, a total of forty-eight overweight and obese females consumed a fixed lunchtime meal. Their ad libitum energy intake of high-energy snack food was observed during a second laboratory session that occurred later that day. In the focused-attention condition, participants ate their lunch while listening to audio instructions that encouraged them to pay attention to the food being eaten. In a control condition, participants ate while listening to an audio book with a neutral (non-food-related) content. To test whether focused attention influenced food intake via enhancing the memory of the earlier consumed meal, we measured the participants' memory of their lunchtime meal. Ad libitum snack intake was approximately 30 % lower for participants in the focused-attention condition than for those in the control condition, and this difference was statistically significant. There was limited evidence that attention decreased later food intake by enhancing memory representation of the earlier consumed meal. Eating attentively can lead to a substantial decrease in later energy intake in overweight and obese individuals. Behavioural strategies that encourage a more 'attentive' way of eating could promote sustained reductions in energy intake and weight loss.

Clarifying the roles of homeostasis and allostasis in physiological regulation

Homeostasis, the dominant explanatory framework for physiological regulation, has undergone significant revision in recent years, with contemporary models differing significantly from the original formulation. Allostasis, an alternative view of physiological regulation, goes beyond its homeostatic roots, offering novel insights relevant to our understanding and treatment of several chronic health conditions. Despite growing enthusiasm for allostasis, the concept remains diffuse, due in part to ambiguity as to how the term is understood and used, impeding meaningful translational and clinical research on allostasis. Here, we provide a more focused understanding of homeostasis and allostasis by explaining how both play a role in physiological regulation, and a critical analysis of regulation suggests how homeostasis and allostasis can be distinguished. Rather than focusing on changes in the value of a regulated variable (e.g., body temperature, body adiposity, or reward), research investigating the activity and relationship among the multiple regulatory loops that influence the value of these regulated variables may be the key to distinguishing homeostasis and allostasis. The mechanisms underlying physiological regulation and dysregulation are likely to have important implications for health and disease.

The evolution of the Society for the Study of Ingestive Behavior (SSIB)

This review summarizes the formation of the Society for the Study of Ingestive Behavior (SSIB), highlighting the many people whose commitment and perseverance brought together a wide range of disciplines for the common goal of investigating ingestive behavior and providing communication via scientific meetings. The goals and philosophy of the Society today are described along with the challenges it will face in the future. It concludes with the important message that excellence in science, combined with commitment to, and participation from, younger investigators, will ensure its continued success. The SSIB was officially incorporated on March 30, 1987 to serve a unique niche within the biological and behavioral sciences. Its initial vision was to serve as the "leading scientific organization for the study of ingestive behavior". This mission continues to drive the philosophy of the Society which currently boasts over 350 members representing 30 different countries. The SSIB melded scientific disciplines that included physiological and psychological aspects of food and fluid intake, as well as taste and olfaction. Prior to its creation, scientists from each of these disciplines met at several key conferences, most notably The International Conference on the Physiology of Food and Fluid Intake, a now defunct satellite of the International Union of Physiological Sciences, and The Eastern Psychological Association. From these and other smaller conferences came the idea of forming a society that integrated research from the biological, psychological and social aspects of food and fluid intake in both animals and humans. While this emphasis of the Society remains today, changing scientific priorities and interests continue to shape and influence the direction of the Society. Since its first meeting held at Princeton University in NJ in 1992, the annual meeting has become a major means of disseminating cutting-edge information on current research in the field of ingestive behavior. The record of its programs provides a valuable window into the workings of what was then a new scientific discipline and its evolution over time which may be useful, not only to members of the SSIB, but also to students of the history of science.

Dietary strategies to increase satiety

Obesity has a multifactorial etiology. Although obesity is widespread and associated with serious health hazards, its effective prevention and treatment have been challenging. Among the currently available treatment approaches, lifestyle modification to induce a negative energy balance holds a particularly larger appeal due to its wider reach and relative safety. However, long-term compliance with dietary modifications to reduce energy intake is not effective for the majority. The role of many individual nutrients, foods, and food groups in inducing satiety has been extensively studied. Based on this evidence, we have developed sample weight-loss meal plans that include multiple satiating foods, which may collectively augment the satiating properties of a meal. Compared to a typical American diet, these meal plans are considerably lower in energy density and probably more satiating. A diet that exploits the satiating properties of multiple foods may help increase long-term dietary compliance and consequentially enhance weight loss.

The role of psychobiological and neuroendocrine mechanisms in appetite regulation and obesity

Obesity is a multifactorial disease. Among its causes are physical inactivity and overeating. In addition, other factors may play an important role in the development of overweight/obesity. For example, certain hormones including leptin, insulin and ghrelin, may influence appetite and consequently body weight. Obesity frequently co-exists with metabolic disorders including dyslipidemia, hypertension and insulin resistance, thus constituting the metabolic syndrome which is characterized by increased cardiovascular risk. Lack of comprehensive knowledge on obesity-related issues makes both prevention and treatment difficult. This review considers the psychobiological and neuroendocrine mechanisms of appetite and food intake. Whether these factors, in terms of obesity prevention and treatment, will prove to be relevant in clinical practice (including reducing the cardiovas-cular risk associated with obesity) remains to be established.

Leptin reverses declines in satiation in weight-reduced obese humans

BACKGROUND

Individuals who are weight-reduced or leptin deficient have a lower energy expenditure coupled with higher hunger and disinhibition and/or delayed satiation compared with never-weight-reduced control subjects. Because exogenous leptin inhibits feeding in congenitally leptin-deficient humans, reduced leptin signaling may reduce the expression of feeding inhibition in humans.

OBJECTIVE

The objective was to test the hypothesis that reduced leptin signaling may reduce the expression of feeding inhibition (ie, blunt satiation) in humans by examining the effects of leptin repletion on feeding behavior after weight loss.

DESIGN

Ten obese humans (4 men, 6 women) were studied as inpatients while they received a weight-maintaining liquid-formula diet. Satiation was studied by measuring intake and ratings of appetite-related dispositions 3 h after ingestion of 300 kcal of the liquid-formula diet. The subjects were studied at each of 3 time periods: 1) while they maintained their usual weight (Wt(initial)) and then after weight reduction and stabilization at 10% below initial weight and while they received 5 wk of either 2) twice-daily injections of placebo (Wt(-10%placebo)) or 3) "replacement doses" of leptin (Wt(-10%leptin)) in a single-blind crossover design with a 2-wk washout period between treatments. Energy expenditure was also measured at each study period.

RESULTS

Both energy expenditure and visual analog scale ratings that reflect satiation were significantly lower at Wt(-10%placebo) than at Wt(initial) and Wt(-10%leptin).

CONCLUSION

The results are consistent with the hypothesis that the absence of leptin signaling after weight loss may blunt the expression of feeding inhibition in humans.

Perception as Interacting Psychophysical Functions. Could the Configuring of Features Replace a Specialised Receptor?

This paper illustrates how perception is achieved through interactions among the psychophysical functions of judged features of an object. The theory is that the perceiver places processed features in a multidimensional space of discriminal processes. Each dimension is scaled in units of discrimination performance. The zero coordinate of each feature is its level in an internal standard (norm) established by previous experience of that category of object in context. Experiments are reported which show that one, two, or three concurrent single-featured objects matched the multiple features of another object in two ways. Either stimulation from the two objects had discrimination distances from norm that added, or the stimulation by one object was processed through a concept describing stimulation by the other object. It follows that, in this case, perception via a receptor for the multi-featured object can be replaced by a point of balance among receptors for each single feature. The object with its own receptor is the gustatory stimulant L-glutamic acid as its monosodium salt. The features that stimulate diverse gustatory receptors of their own are sodium chloride, citric acid, sucrose, and caffeine. A more complex approach to dimensional coding was developed earlier for photoreceptors in colour judgments. The present approach is modality independent, mathematically simple, and economical in experimental data.

Targeting cultural changes supportive of the healthiest lifestyle patterns. A biosocial evidence-base for prevention of obesity

This paper argues that the rise in obesity can be slowed only by universal education based on a type of evidence that does not yet exist. On top of literacy and numeracy, people need the ability to preempt the fattening effect of a decrease in habitual physical activity by altering familiar patterns of eating, drinking and exercise in ways that are both maintainable within the individual's social and physical environment and also effective at decreasing weight to the asymptote for each sustained change. Hence the prevention of obesity requires locally valid evidence on which changes to specific customary habits actually do avoid unhealthy fattening. Interventions need to focus on antecedents to individuals' common lapses from the healthy changes in these customs. Yet no research has been funded into the public's descriptions of feasible changes that cause a step down in weight, let alone into the environmental conditions for individuals' maintenance of those changes. As a result, public health policies on obesity lack scientific basis. When will a start be made on systematic identification of cultural supports to readily executed patterns of lifestyle behaviour which improve health to extents that have been directly measured?

Learnt reduction in the size of a meal. Measurement of the sensory-gastric inhibition from conditioned satiety

Many experiments on the role of learning in the amount eaten at a distinctive test meal have been claimed to observe "conditioned satiety." None published from outside this author's group has used either the necessary design of the contingencies to be learnt or the measurements that distinguish a sating effect from other loss of interest in food. One experiment has just been published without an adequate design but giving the best evidence yet from another group for the conditioning of sensory-gastric satiety; yet the authors conclude for changes in sensory preference with no learnt gastric involvement in the meal size response. To encourage correct use of the demonstrations in rats, monkeys and people of conditioned satiety and its mechanism, this paper briefly reviews publications that attribute control of meal size to learnt satiety.