What is binge eating disorder?

Binge eating disorder (BED) is characterized by recurring episodes of binge eating that occur without compensatory behavior. It is associated with a reduced quality of life and being overweight/obese. Binge eating episodes are characterized by a lack of control and imply difficulties in self-control processes. These difficulties suggest that mechanisms of cognitive and emotional dysfunction play a role in the development and maintenance of BED. Cognitive functioning (CoF) involves aspects of perception, thinking, reasoning, and remembering. Research has already shown that defects in CoF play a role in anorexia and bulimia nervosa. Emotional functioning (EmF) includes emotion regulation (ER) and emotional awareness (EA). Defects play a role in anorexia and bulimia nervosa. Research shows that binge eating episodes are linked to CoF and EmF processes. The escape theory states that cognitive processes are influenced by emotional states through a decrease of awareness when experiencing negative emotions. The ironic process theory states that cognitive processes influence emotional states when confronted with stressors. The purpose of this review is to critically summarize the current state of research on CoF and EmF in individuals with BED compared to 1) healthy controls and individuals with anorexia or bulimia, and 2) normal-weight and overweight/obese individuals without an eating disorder.

Which method was used in this meta-analysis?

To be included in this study, studies had to: 1) include a sample of individuals with BED, 2) provide statistical comparisons with healthy controls, individuals with other eating disorders, or overweight people, 3) be published in English or German. Adult only samples were selected.

How many studies were used?

A total of 57 studies were used. The majority of studies featured an all female sample.

What did studies find for CoF with neutral stimuli?

There were 12 studies of CoF with neutral stimuli. In six studies, inhibition was measured including the Stroop color-word task and a Stop Signal Task, among others. No differences were found between individuals with BED and obese people or people with normal weight. Four studies measured flexibility using neuropsychological tests. In one study, subjects with BED took longer to complete a task than people with normal weight or people who were obese, but this did not apply to two other studies. The results were therefore heterogeneous, depending on the study and the tasks that were used. Working memory was investigated in two studies. The results were inconsistent for verbal working memory, and individuals with BED did not differ from an obese control group regarding visual working memory. Verbal memory was investigated in one study, and no differences were found between BED and obese people. Decision making was investigated in five studies, with inconsistent results. Regarding delay of gratification, no differences were found between the BED group and the obese/normal weight control group. Regarding planning and problem solving, obese individuals with BED achieved lower outcomes and made more mistakes than obese controls.

Which effects were found on the level of neurophysiology?

People with BED showed reduced prefrontal and insular processing in a Monetary Loss Task in comparison to obsese/normal weight controls. Obese controls showed increased ventral stratial and prefrontal activity compared to normal weight controls. During the Stroop Task, people with BED exhibit diminished activity in the prefrontal cortex, insula and frontal gyrus compared to obese/normal weight controls.

Which effects were found in studies using self-report measures?

Obese individuals with BED reported more difficulty in overriding or changing dominant inner responses and interrupting undesired behavioral tendencies compared to obese/normal weight controls.

What did studies find for CoF with disorder-related stimuli?

In terms of attention and flexibility with food- and body-related stimuli, no differences were found between obese individuals with BED and obese and normal weight controls. BED is associated with inhibitions deficits in the context of disorder-related stimuli. They also experience more cognitive interference in working memory. People with BED also have a specific eating-related memory bias, and they remember fewer positive body-related words than people without BED. There are general difficulties in delaying gratification for people with BED, not just food-specific difficulties.

Which effects were found on the level of neurophysiology?

Obese individuals with BED show more ongoing and conscious attention allocation towards food stimuli than controls. They are also more focused on body parts that they see as ugly. Individuals with BED showed more frequent fixations of their own body pictures and less frequent fixations of control body pictures compared with overweight controls, while overweight controls demonstrated longer fixation of control body pictures than did individuals with BED. The activity in the orbitofrontal cortex is greater for individuals with BED, and there is reduced activity in the striatum and the ACC compared to controls. Obese individuals with BED also have a hyper-responsive reward system, with an increased release of dopamine, compared to obese controls. 

What was found in studies focused on emotion regulation?

What was found for emotion regulation in experimental designs?

Two studies looked at emotion regulation as a mediator in the link between negative emotions and eating behavior. Subjects had to watch videos that provoke negative emotions, and had to either suppress or reappraise those emotions. Suppressing emotions led to a desire to binge eat in individuals with BED, while reappraisal did not. Regarding interpersonal problem-solving ability, no differences were found with BED and overweight/obese controls regarding the number of generated relevant solutions. However, the solutions proposed by individuals with BED were significantly less effective and specific compared to those generated by controls.

What was found for emotion regulation in designs using self-report measures?

A lower capacity to express positive feelings was associated with a higher probability of BED, and obese individuals with BED have a higher tendency to express anger. Two studies found that obese individuals with BED suppressed their emotions more often than the control group and used reappraisal less often. People with BED and anorexia nervosa report fewer positive thoughts and mindful observations. People with eating disorders show more self-criticism, difficulties with goal-directed behavior and impulse control. However, people with BED have fewer suicidal thoughts, difficulties with goal-directed behavior and impulse control compared to individuals with anorexia and bulimia nervosa.

What was found for studies focused on emotional awareness?

Alexithymia occurs in 24.1% to 62.5% of people with BED, with a particular difficulty in identifying and describing feelings. People with BED also reported more problems with interoceptive awareness. In summary, it can be said that with regards to emotional functioning, individuals with BED 1) experience similar difficulties as individuals with anorexia and bulimia, but these difficulties are less severe with BED, 2) the difficulties are greater than those of obese/normal-weight controls.

Which conclusions can be drawn?

Regarding CoF, obese individuals with BED did not differ from obese/normal-weight controls in tasks using neutral stimuli. However, when these tasks were performed with disorder-related stimuli, people with BED scored lower. In particular, there is an increased food-related reward sensitivity in BED, especially for high-caloric foods. There are also stronger responses in reward areas in the brain. More research is needed into the differences between individuals with BED and individuals with anorexia or bulimia. The increased sensitivity to rewards in the area of ​​food, and deficiencies in delaying gratification, could impede people with BED to adhere to their plans not to eat certain foods or exercise more, and thus contribute to maintaining the disorder. People with BED also have a bias towards their own body and ugly body parts. People with BED also have difficulty with food-related response inhibition, and differences in prefrontal and orbitofrontal brain regions are visible. With regard to EmF, people with BED experience the same problems as people with anorexia or bulimia, but these problems are less serious with BED. Problems with emotion regulation can lead to binge eating in response to negative affect. People with BED might have deficits in differentiating between feelings and sensations of hunger/satiety which can induce emotional eating. The interaction between CoF and EmF has only been measured in one study, finding more disadvantageous decision making after increased negative affect. 

What do these results imply regarding research and clinical practice?

Little is known about which specific aspects of CoF and EmF are altered in BED. Future research should investigate this. It is also difficult to determine whether changes in CoF and EmF are due to comorbid obesity or the increased eating disorder psychopathology in BED. The most important thing for future research, however, is to investigate the interaction between CoF and EmF in BED. There are also clinical implications. For example, interventions that focus directly on CoF could be used in the treatment of BED. Treatments that focus on attentional bias could also be promising. Regarding emotion regulation, there is already a treatment for BED that targets this, namely dialectical behavior therapy. Future treatments should focus on CoF and EmF, and not just on the main symptoms of BED and psychopathology.

BulletPoint Summary

• Binge eating disorder (BED) is characterized by recurring episodes of binge eating that occur without compensatory behavior. Binge eating is characterized by a lack of control and implies difficulties in self-control processes. These difficulties suggest that mechanisms of cognitive and emotional dysfunction play a role in the development and maintenance of BED. 

• The escape theory states that cognitive processes are influenced by emotional states through a decrease of awareness when experiencing negative emotions. The ironic process theory states that cognitive processes influence emotional states when confronted with stressors.

• The review at hand investigated the influence of cognitive functioning (CoF) and emotional functioning (EmF).

• Regarding CoF, obese individuals with BED did not differ from obese/normal-weight controls in tasks using neutral stimuli. However, when these tasks were performed with disorder-related stimuli, people with BED scored lower. In particular, there is an increased food-related reward sensitivity in BED, especially for high-caloric foods. There are also stronger responses in reward areas in the brain. The increased sensitivity to rewards in the area of ​​food, and deficiencies in delaying gratification, could impede people with BED to adhere to their plans not to eat certain foods or exercise more, and thus contribute to maintaining the disorder. People with BED also have a bias towards their own body and ugly body parts. People with BED also have difficulty with food-related response inhibition, and differences in prefrontal and orbitofrontal brain regions are visible.

• With regard to EmF, people with BED experience the same problems as people with anorexia or bulimia, but these problems are less serious with BED. Problems with emotion regulation can lead to binge eating in response to negative affect. People with BED might have deficits in differentiating between feelings and sensations of hunger/satiety which can induce emotional eating. The interaction between CoF and EmF has only been measured in one study, finding more disadvantageous decision making after increased negative affect. 

• Future research should investigate which specific aspects of CoF and EmF are altered in BED, determine whether changes in CoF and EmF are due to comorbid obesity or the increased eating disorder psychopathology, and investigate the interaction between CoF and EmF. Future treatments should focus on CoF and EmF, and not just on the main symptoms of BED and psychopathology.