Cognitive control of eating

Food Restriction in Anorexia Nervosa in the Light of Modern Learning Theory: A Narrative Review

Improvements in the clinical management of anorexia nervosa (AN) are urgently needed. To do so, the search for innovative approaches continues at laboratory and clinical levels to translate new findings into more effective treatments. In this sense, modern learning theory provides a unifying framework that connects concepts, methodologies and data from preclinical and clinical research to inspire novel interventions in the field of psychopathology in general, and of disordered eating in particular. Indeed, learning is thought to be a crucial factor in the development/regulation of normal and pathological eating behaviour. Thus, the present review not only tries to provide a comprehensive overview of modern learning research in the field of AN, but also follows a transdiagnostic perspective to offer testable explanations for the origin and maintenance of pathological food rejection. This narrative review was informed by a systematic search of research papers in the electronic databases PsycInfo, Scopus and Web of Science following PRISMA methodology. By considering the number and type of associations (Pavlovian, goal-directed or habitual) and the affective nature of conditioning processes (appetitive versus aversive), this approach can explain many features of AN, including why some patients restrict food intake to the point of life-threatening starvation and others restrict calorie intake to lose weight and binge on a regular basis. Nonetheless, it is striking how little impact modern learning theory has had on the current AN research agenda and practice.

Assessing dietary intake: Who, what and why of under-reporting

Under-reporting of food intake is one of the fundamental obstacles preventing the collection of accurate habitual dietary intake data. The prevalence of under-reporting in large nutritional surveys ranges from 18 to 54% of the whole sample, but can be as high as 70% in particular subgroups. This wide variation between studies is partly due to different criteria used to identify under-reporters and also to non-uniformity of under-reporting across populations. The most consistent differences found are between men and women and between groups differing in body mass index. Women are more likely to under-report than men, and under-reporting is more common among overweight and obese individuals. Other associated characteristics, for which there is less consistent evidence, include age, smoking habits, level of education, social class, physical activity and dietary restraint. Determining whether under-reporting is specific to macronutrients or food is problematic, as most methods identify only low energy intakes. Studies that have attempted to measure under-reporting specific to macronutrients express nutrients as percentage of energy and have tended to find carbohydrate under-reported and protein over-reported. However, care must be taken when interpreting these results, especially when data are expressed as percentages. A logical conclusion is that food items with a negative health image (e.g. cakes, sweets, confectionery) are more likely to be under-reported, whereas those with a positive health image are more likely to be over-reported (e.g. fruits and vegetables). This also suggests that dietary fat is likely to be under-reported. However, it is necessary to distinguish between under-reporting and genuine under-eating for the duration of data collection. The key to understanding this problem, but one that has been widely neglected, concerns the processes that cause people to under-report their food intakes. The little work that has been done has simply confirmed the complexity of this issue. The importance of obtaining accurate estimates of habitual dietary intakes so as to assess health correlates of food consumption can be contrasted with the poor quality of data collected. This phenomenon should be considered a priority research area. Moreover, misreporting is not simply a nutritionist's problem, but requires a multidisciplinary approach (including psychology, sociology and physiology) to advance the understanding of under-reporting in dietary intake studies.

Impulsivity and inhibitory control deficits are associated with unhealthy eating in young adults

Heightened impulsivity and inefficient inhibitory control are increasingly recognized as risk factors for unhealthy eating and obesity but the underlying processes are not fully understood. We used structural equation modeling to investigate the relationships between impulsivity, inhibitory control, eating behavior, and body mass index (BMI) in 210 undergraduates who ranged from underweight to obese. We demonstrate that impulsivity and inhibitory control deficits are positively associated with several facets of unhealthy eating, including overeating in response to external food cues and in response to negative emotional states, and making food choices based on taste preferences without consideration of health value. We further show that such unhealthy eating is, for the most part, associated with increased BMI, with the exception of Restraint Eating, which is negatively associated with BMI. These results add to our understanding of the impact of individual differences in impulsivity and inhibitory control on key aspects of unhealthy eating and may have implications for the treatment and prevention of obesity.

Fighting food temptations: the modulating effects of short-term cognitive reappraisal, suppression and up-regulation on mesocorticolimbic activity related to appetitive motivation

The premise of cognitive therapy is that one can overcome the irresistible temptation of highly palatable foods by actively restructuring the way one thinks about food. Testing this idea, participants in the present study were instructed to passively view foods, up-regulate food palatability thoughts, apply cognitive reappraisal (e.g., thinking about health consequences), or suppress food palatability thoughts and cravings. We examined whether these strategies affect self-reported food craving and mesocorticolimbic activity as assessed by functional magnetic resonance imaging. It was hypothesized that cognitive reappraisal would most effectively inhibit the mesocorticolimbic activity and associated food craving as compared to suppression. In addition, it was hypothesized that suppression would lead to more prefrontal cortex activity, reflecting the use of more control resources, as compared to cognitive reappraisal. Self-report results indicated that up-regulation increased food craving compared to the other two conditions, but that there was no difference in craving between the suppression and cognitive reappraisal strategy. Corroborating self-report results, the neuroimaging results showed that up-regulation increased activity in important regions of the mesocorticolimbic circuitry, including the ventral tegmental area, ventral striatum, operculum, posterior insular gyrus, medial orbitofrontal cortex and ventromedial prefrontal cortex. Contrary to our hypothesis, suppression more effectively decreased activity in the core of the mesocorticolimbic circuitry (i.e., ventral tegmental area and ventral striatum) compared to cognitive reappraisal. Overall, the results support the contention that appetitive motivation can be modulated by the application of short-term cognitive control strategies.

Amygdala subsystems and control of feeding behavior by learned cues

A combination of behavioral studies and a neural systems analysis approach has proven fruitful in defining the role of the amygdala complex and associated circuits in fear conditioning. The evidence presented in this chapter suggests that this approach is also informative in the study of other adaptive functions that involve the amygdala. In this chapter we present a novel model to study learning in an appetitive context. Furthermore, we demonstrate that long-recognized connections between the amygdala and the hypothalamus play a crucial role in allowing learning to modulate feeding behavior. In the first part we describe a behavioral model for motivational learning. In this model a cue that acquires motivational properties through pairings with food delivery when an animal is hungry can override satiety and promote eating in sated rats. Next, we present evidence that a specific amygdala subsystem (basolateral area) is responsible for allowing such learned cues to control eating (override satiety and promote eating in sated rats). We also show that basolateral amygdala mediates these actions via connectivity with the lateral hypothalamus. Lastly, we present evidence that the amygdalohypothalamic system is specific for the control of eating by learned motivational cues, as it does not mediate another function that depends on intact basolateral amygdala, namely, the ability of a conditioned cue to support new learning based on its acquired value. Knowledge about neural systems through which food-associated cues specifically control feeding behavior provides a defined model for the study of learning. In addition, this model may be informative for understanding mechanisms of maladaptive aspects of learned control of eating that contribute to eating disorders and more moderate forms of overeating.

Amygdalo-hypothalamic circuit allows learned cues to override satiety and promote eating

Organisms eat not only in a response to signals related to energy balance. Eating also occurs in response to "extrinsic," or environmental, signals, including learned cues. Such cues can modify feeding based on motivational value acquired through association with either rewarding or aversive events. We provide evidence that a specific brain system, involving connections between basolateral amygdala and the lateral hypothalamus, is crucial for allowing learned cues (signals that were paired with food delivery when the animal was hungry) to override satiety and promote eating in sated rats. In an assessment of second-order conditioning, we also found that disconnection of this circuitry had no effect on the ability of a conditioned cue to support new learning. Knowledge about neural systems through which food-associated cues specifically control feeding behavior provides a defined model for the study of learning that may be informative for understanding mechanisms that contribute to eating disorders and more moderate forms of overeating.

Dietary restraint and self-reported meal sizes: diary studies with differentially informed consent

Psychometric methods were used to explore the reliability and criterion validity of self-reported food intake in studies of dietary restraint. In Study 1 the reliabilities over days of daily aggregate intakes and of intakes at meals at particular times of day were assessed in 7 day food diaries by 27 low-BMI females. The sizes of particular meals correlated poorly with each other and with the total of all other meals; daily aggregate intakes also had poor reliability (Cronbach's alpha). Individuals meal sizes were consistent from day to day, with high inter-correlations between meal sizes, high correlations between meals at particular times and the sum of the remainder and high reliabilities. Aggregate intake had moderate criterion validity. Of individual meals, only breakfast achieved criterion validity, but there was a significant cubic component in its relationship with restraint. In Study 2, young male and female participants with various BMIs, completed a food diary on a single day. Again, aggregate daily intake had low reliability. Total intake and breakfast both had criterion validity, dietary restraint correlating negatively with total intake and breakfast size in the whole sample and in females, but there were significant quadratic components in the relationships. In contrast, restraint correlated positively with lunch size in the whole sample and in males. The combination of low reliability of individual meals as estimates of total intake, and the low criterion validity of all meals except breakfast, suggests that it may be inappropriate to study dietary restraint using aggregate self-reported intake measures.

The assessment of obesity: theoretical background and practical advice

Developments in understanding the causes and consequences of obesity have important implications for the assessment of weight problems. Simple measurement of body weight is no longer sufficient. The evaluation should include measures of body composition, dietary quality, energy expenditure, risk factor status and body image. In this paper, the arguments in favour of a broader-based evaluation of obesity are presented and a range of assessment methods are discussed.

The role of restraint and disinhibition in appetite control

Fifty-six women classified according to their restraint and disinhibition scores, using Stunkard and Messick's (1985) Eating Questionnaire, participated in an experiment in which the proportion of carbohydrate in a prepared meal and the knowledge provided to them about its contents were varied. Measures were taken of their desire for food and their willingness to eat, as well as the total intake and the amount of carbohydrate and of protein they ate at an ad libitum test meal 4 hr later. While the results do not support the argument that laboratory-induced counter-regulatory eating can be attributed to disinhibition, they emphasize the usefulness of our experimental model which allows the interaction of dietary, cognitive and personality factors to be examined concurrently in investigations of appetite control.

Cognitive-behavioural treatments for obesity

The effects of the original behavioural treatment have been studied exhaustively and the limits of this very useful approach have been delineated. Further developments have largely come from combining it with other modes of treatment or from delivering it in more intensive ways. The knowledge base has been limited to operant psychology, despite the fact that study of the psychology of appetite has developed extensively in the two decades since Stuart's original paper of 1967 (Stuart RB. Behavioral control of overeating. Behav Res Ther 1967; 5: 357-365). Many fundamental processes such as the role of conditioning in the development of satiety, and the effects of monotony and variety, have important implications for the treatment of obesity which have yet to be explored.