Body image disturbance (BID) is a common symptom in patients with eating disorders. The onset is mainly attributed to patients with anorexia nervosa who persistently tend to subjectively discern themselves as average or overweight despite adequate, clinical grounds for a classification of being severely underweight. The symptom is an altered perception of one's body and a severe state of bodily dissatisfaction characterizing the body image disturbance. It is included among the diagnostic criteria for anorexia nervosa in DSM-5 (criterion C). The disturbance is associated with significant bodily dissatisfaction and is a source of severe distress, often persisting even after seeking treatment for an eating disorder, and is regarded difficult to treat. Thus, effective body image interventions could improve the prognosis in patients with ED, as experts have suggested. Unfortunately, there is no hard evidence that current treatments for body image disturbance effectively reduce eating disorders' symptoms. Furthermore, pharmacotherapy is ineffective in reducing body misperception and it has been used to focus on correlated psychopathology (e.g., mood or anxiety disorders). However, to date, research and clinicians are developing new therapies as virtual reality experiences, mirror exposure or multisensory integration body techniques, which have shown some extent of efficacy.
German-American psychiatrist Hilde Bruch first identified and described body image disturbance in anorexia nervosa. In her famous article "Perceptual and Conceptual Disturbances in Anorexia Nervosa"  she wrote:
What is pathognomic of anorexia is not the severity of the malnutrition per se—equally severe degrees are seen in other malnourished psychiatric patients—but rather the distortion of body image associated with it: the absence of concern about emaciation, even when advanced, and the vigor and stubbornness with which the often gruesome appearance is defended as normal and right, not too thin, and as the only possible security against the dreaded fate of becoming fat.
However, body image disturbance is not specific to anorexia nervosa but is sometimes present in other eating disorders such as bulimia nervosa and binge eating disorder. Furthermore, recent studies have shown that it is possible to observe alterations in the perception of one's body, even in healthy subjects. Suggesting that a slightly altered perception of the body is a normal part of everyone's life and manifests itself more intensely in more vulnerable individuals (e.g., patients with eating disorders). Commonly, body image disturbance is confused with body dysmorphic disorder, an obsessive-compulsive disorder with whome it share some features.
Body image disturbance is a multifaceted construct including both perceptual and attitudinal issues. Some of the more common signs are:
Clinically speaking, a growing body of research suggests that body image disturbance plays a significant role in the onset, maintenance, and relapse of anorexia nervosa, as previously suggested by Hilde Bruch in 1962. However, despite increasing evidence, a recent review stated that the available empirical data are still insufficient and "provide no basis to answer the question whether body image disturbance is a (causal) risk factor for anorexia nervosa". As suggested by the authors, this lack of evidence is partly related to terminology problems used in the body image field.
Different labels are used in research and clinical setting to define the body image disturbance generating terminological confusion. Some of the most used terms are "body image discrepancy", "body image self-discrepancy", "body image distortion", "disturbed body image", "disturbances in body estimations", "body image disturbance", and "negative body image". Sometimes, the term "body dissatisfaction" is also used to refer to body image disturbance indiscriminately. Moreover, the DSM-5 itself defines this symptom vaguely: "a disturbance in the way one's body weight or shape is experienced". Thus, the lack of a clear definition is problematic from both a clinical and basic research point of view.
However, most recent studies define "body image disturbance" as a multidimensional symptom of various components associated with body image. Specifically, we usually describe body image as a concept formed by the interaction of four body-related components: cognitive, affective, behavioral, and perceptual.
All of these components are altered in body image disturbance:
In 2021, Artoni and colleagues consistently proposed a more clarifying definition of body image disturbance, as part of research. The authors suggested using the term "bodily dissatisfaction" when there are alterations in the body image's affective, cognitive, and behavioral components and strictly using "body image disturbance" only when all four components are altered, including the perceptual one. In short, they define body image disturbance as when an altered perception of the shape and weight of one's body is present and aggravates body dissatisfaction. The term is literally consistent with DSM-5 description "a disturbance in the way weight and body shapes are experienced"  and it is therefore "preferable to others".
Patients with body image disturbance exhibit an altered conscious representation of their bodies. This representation is a third-person perspective, more precisely an allocentric representation of the body, which means how the body's image is stored in the memory. This representation is evoked in self-image tasks, such as comparing one's body with others or drawing one's body shapes. However, in patients with anorexia nervosa and bulimia nervosa, this mental representation of the body is frequently overextended compared to the actual body shapes. Also, patients with anorexia nervosa show negative thoughts about their body, such as "I'm too fat," "I'm horrible," and other negative body-related thoughts. In some cases, however, the ideal internalized body has canons of pathological thinness (e.g., a body without female shapes or "that communicates suffering"). A "sick body" could be a critical maintenance factor, generating more attention from family members, reducing the requests and expectations of others, and sexual attractiveness (especially in patients with sexual trauma).
Affective alterations concern the feelings and emotions experienced towards one's body. Body dissatisfaction is frequently present, sometimes related to anxiety and shame when the body is exposed or gazed at in a mirror. In some cases, anger and feelings of aggression towards one's body are reported. Congruent with the self-objectification theory, one's body is frequently experienced only as an "object to be modified" and not as a "subject to take care of". Fear is associated with the idea of getting fat.
The behavioral component of body image disturbance contemplates different body-checking behaviors such as repeatedly weighing during the day, spending much time in front of the mirror or avoiding it, frequently taking selfies, checking parts of the body with hands (e.g. circumference of the wrists, arms, thighs, belly or hips). Other behaviors are avoiding situations in which the body is exposed (for example, the swimming pool or the sea), and wearing very loose and covering clothes. More generally, avoidance of bodily sensations, particularly the interoceptive ones, is reported.
In body image disturbance, several perceptual domains are altered. Visual perception is the most studied, but research found misperceptions in other sensory domains such as haptic, tactile, affective-touch. Also, the body schema is overextended. Some research suggested that this is related to a general enlarged mental representation of body size. A recent study published on Nature also highlighted how a perceptual disturbance is present in subjects recovered from anorexia nervosa even without affective-cognitive body concerns. Finally, interoception, the "sense of the physiological condition of the body" is problematic in eating disorders.
The age of onset for body image disturbance is often early adolescence, age in which the comparison with peers becomes significant and leads to a greater sensitivity towards criticism and teasing about one's physical appearance. Furthermore, puberty leads to rapid changes in body size and shape that need to be integrated into the body image. For this reason, adolescence is considered a critical age, with a greater vulnerability to internalizing ideals of thinness, to develop body dissatisfaction, body image disturbance  and eating disorders. In a recent review, eight on-topic studies were analyzed. The authors found that most adolescents with anorexia nervosa and bulimia nervosa already had body-checking behaviors, negative body-related emotions and feelings, low body satisfaction, and an altered estimate of their body size compared to healthy controls. Unfortunately, how one passes from an initial dissatisfaction with one's body to an actual perceptual disorder is still unknown despite its clinical relevance.
Body dissatisfaction and body image disturbance are closely related. Personal, interpersonal, cultural, social, and ethnic variables largely influence bodily dissatisfaction, influencing the emergence of painful feelings towards one's body. In addition, social pressure is considered a risk factor for body dissatisfaction. For example, the frequent presence on media of thin female bodies determines, especially in young girls, a daily comparison between their bodies and models and actresses favoring bodily dissatisfaction; comparing an "ideal" and "real" body feed an intense dissatisfaction with one's body and increases the feeling of shame, disgust, and anxiety towards the one's body and appearance.
Dissatisfaction with one's body involves only three of the four components of the body image. Those suffering from bodily dissatisfaction can have negative thoughts about one's body (e.g., "I'm ugly" or "I'm too short"). In addition, they may have behaviors related to bodily dissatisfaction (e.g., going on a diet or resorting to cosmetic surgery) . They may also have negative feelings of dissatisfaction with their body and be ashamed of showing it in public. However, all these aspects are not enough to define it as a body image disturbance. In fact, there is no perceptual alteration of one's body. Thus, body image disturbance cannot be overlapped by body dissatisfaction, but they are closely related.
Body image disturbance in anorexia and body dysmorphic disorder are similar psychiatric conditions that involve an altered perception of the body or parts of it but are not the same disorder. Body image disturbance is a symptom of anorexia nervosa and is present as criterion C in the DSM-5, and alters the perception of weight and shapes of the whole body. Patients with anorexia believe that they are overweight, perceive their body as "fat" and misperceive their body shapes. Body dysmorphic disorder is an obsessive-compulsive disorder characterized by disproportionate concern for minimal or absent individual bodily flaws, which cause personal distress and social impairment  Patients with BDD are concerned about physical details, mainly the face, skin, and nose. Thus, both anorexia nervosa and body dysmorphic disorder manifest significant disturbances in body image but are different and highly comorbid. For example, Grant and colleagues reported that 39% of AN patients in their sample had a comorbid diagnosis of body dysmorphic disorder, with concerns unrelated to weight. Cereaet et al., reported that 26% of their AN sample had a probable BDD diagnosis with non-weight-related body concerns.
Previous studies found that both BDD and eating disorder groups were similar in body dissatisfaction, body checking, body concerns, and levels of perfectionism. Furthermore, both BDD and AN patients report higher intensities of negative emotions, lower intensities of positive emotions, lower self-esteem, and anxiety symptoms. Moreover, we find severe concerns about one's appearance, leading to a continuous confrontation with others' bodies in both diseases. In addition, body image disturbances and body dysmorphic disorder generally onset during adolescence. Finally, alterations in visual processes seems to be present in both disorders, with greater attention to detail and difficulty in perceiving stimuli holistically. Indeed neurophysiology and neuroimaging research suggests similarities between BDD and AN patients in terms of abnormalities in visuospatial processing.
Despite many similarities, the two disorders also have significant differences. The first is gender distribution. Body image disturbance is much more present in females, unlike BDD, which has a much less unbalanced relationship between men and women. Furthermore, those with dysmorphophobia tend to have more significant inhibitions and avoidance of social activities than those suffering from anorexia nervosa. Differences are self-evident when considering the focus of physical concerns and misperception in AN and BDD. Whereas BDD patients report concerns and misperception in specific body areas (mainly face, skin, and hair), in patients with AN the altered perception could involve arms, shoulders, thighs, abdomen, hips, and breasts, and concerns are about the whole body shape and weight. Thus, leading to an alteration of the entire explicit (body image) and implicit (body schema) body's mental representations Furthermore, in anorexia nervosa, not only the visual perception of one's body is altered but also the tactile and interoceptive perception.
Finally, a recent review suggested that the two disorders could be classified as "body image disturbances" (plural) in light of similarities and differences. Although more in-depth studies are needed to confirm this new classification hypothesis.
Body image disturbance is not yet clearly defined by official disease classifications. However, it appears in the DSM-5 under criterion C for anorexia nervosa and is vaguely described as "a disturbance in the way weight and body shapes are experienced". As a result, diagnosis is usually based on reported signs and symptoms; there are still no biological markers for body image disturbance. Numerous psychometric instruments to measure one's body image's cognitive, affective, and behavioral components are used in clinical and research settings, helping in assessing the body image's attitudinal components. Recently, research developed other instruments to measure the perceptive component.
fMRI studies examining brain responses in anorexia nervosa patients to paradigms that include body image tasks have found altered activation across different brain areas, including the prefrontal cortex, precuneus, parietal cortex, insula, amygdala, ventral striatum, extrastriate body area, and fusiform gyrus. However, as Janet Treasure commented, "the research [in the field] is fragmented, and the mechanism of how these areas map onto the functional networks described above needs further study [...] the mechanism by which the extremes of body distortion are driven and circuitry is not known yet."
Historically, research and clinicians have mainly focused on body image disturbance's cognitive, affective, and behavioral components. Consequently, treatments generally target symptoms such as body checking, dysfunctional beliefs, feelings, and emotions relating to the body. One of the best-known psychotherapy in the field is CBT-E. CBT-E is a cognitive-behavioral therapy that has been enhanced with particular strategies to address the psychopathology of eating disorders. These include reducing negative thoughts and worries about body weight and shape, reducing clinical perfectionism, and body-checking behavior. A recent review has shown that CBT-E effectively reduces core symptoms in eating disorders, including concerns about the body. Despite this, the results of CBT-E are no better than other forms of treatment. In fact, a therapy of choice for eating disorders in adults has not yet been identified.
Additionally, two other noteworthy body image treatments are Cash's "Body Image Workbook" and BodyWise. The former is an 8-step group treatment within a classic cognitive-behavioral framework. The latter is a psychoeducational-based treatment improved with cognitive remediation techniques to promote awareness of body image difficulties, reduce cognitive inflexibility, and body dissatisfaction. Worthy of mention is The Body Projectt, an eating disorder prevention program within a dissonant-cognitive framework. The program provides a forum for high school girls and college-age women to confront unrealistic-looking ideals and develop a healthy body image and self-esteem. It has been repeatedly shown to effectively reduce body dissatisfaction, negative mood, unhealthy diet, and disordered eating. The Body Project is therefore not a treatment for eating disorders but a prevention program.
New treatments for body image disturbance have recently been developed, focusing on the disorder's perceptual component. One of the best known is Mirror Exposure. Mirror Exposure is a cognitive-behavioral technique that aims to reduce experiential avoidance, reduce bodily dissatisfaction, and improve one's misperception of one's body. During the exposure, patients are invited to observe themselves in front of a large full-length mirror. There are different types of mirror exposure, guided exposure, unguided exposure, exposure with mindfulness exercises, cognitive dissonance-based mirror exposure. To date, few studies have investigated the effects of mirror exposure in patients with body image disturbance. Key et al. conducted a non-randomized trial in a clinical sample and compared a body image group therapy with or without mirror exposure. They found a significant improvement in body dissatisfaction only in the mirror exposure therapy group. Despite the positive evidence, a recent review suggests that Mirror Exposure has a low-to-medium effect in reducing body image disturbance and further studies are needed to improve it.
Another novelty treatment for body image disturbance is Virtual Reality - Body Swapping. VR-Body Swapping is a technique that allows generating a body illusion during a virtual reality experience. Specifically, after building a virtual avatar using 3D modeling software, it is possible to generate the illusion that the avatar's body is one's own body. The avatar is a 3D human body model that simulates the actual size of the patient and can be modify directly. Some studies have found that applying this technique to anorexia nervosa reduces the misperception of one's body. This treatment is promising but provides, at the moment, only a short-term effect.