Open access peer-reviewed chapter
Abstract
Eating disorder, “a persistent disturbance in eating and its related behaviors” affects both “food consumption and its absorption”, and the overall physical and mental wellbeing of affected individuals. ED is reported worldwide, across gender, ethnical, racial, and socioeconomic strata. Societal emphasis on gender based body-ideals puts extra pressure on adolescents to achieve or maintain unattainable weigh or body shapes, at the cost of them becoming unwell. ED has a complex etiology where an interplay between genetics and environment brings about the onset of symptoms as early as prepubertal years. With their fluctuating and chronic nature, ED may affect perception, emotions, cognition, and behavior. The interface between ED, overeating and obesity, as well as the recent surge in reported cases of ED during Corona pandemic, has focused much attention on eating pathology amongst adolescents. Many adolescents (particularly boys) specially in a prodromal phases of ED, do not yet meet diagnostic thresholds for ED and hence do not receive timely or appropriate professional help. In the current chapter, we aim to 1- address the issues surrounding early recognition of ED symptoms in adolescents under a general umbrella term, “Disordered Eating”, and 2- highlight the importance of societal influence on vulnerable individuals.
Keywords
- eating disorder
- disordered eating
- adolescents
- suicidal ideation
- mental distress
- body ideal
- body size overestimation
- genetic risk score
1. Introduction
Eating is an integral part of multifaceted human survival behavior, but its importance reaches far beyond human physiological necessities. Eating has helped shape human culture throughout history, by the way of food gathering, its preparation or consumption, as well as through its many symbolic attributes, as evident in fasting, either through spiritual rituals or forced by natural forces such as famine [1]. Some historical accounts of fasting practices date back a few centuries, of which the infamous case of Saint Catherine of Siena, would be considered as eating pathology in more modern times [1, 2].
Overweight and obesity have been known phenomena since prehistoric times [3]. Cases of overeating and consequent purging of food (bulimia) amongst the wealthy are recorded as far back in time as the Middle Ages. Scientific recognition of bulimic practices as a pathology started in the early 1900s; however, the first published scientific article on this condition emerged decades later, in 1979, when the possible link between periodic bulimia and pathological undereating was speculated [4].
Earlier scientific speculations on a link between hunger, varying patterns of food consumption from undereating to bulimia and overweight on one hand and emotional state on the other hand were based on, amongst other observations, coexisting history of some adverse childhood experiences in many cases [5]. A wealth of scientific evidence has been since collected on the complex link between physical and psychological aspects of eating behavior in both general and clinical contexts.
Parallel to an increase in the prevalence of both overweight/obesity and overeating/undereating in the past few decades, adolescents seem to be increasingly concerned with their food consumption, weight, or body size. Although in the past few decades, genetic studies have provided ample evidence for the link between obesity, undereating, and overeating, the current understanding of this link stops short of fully explaining the exact mechanisms underlying a pathological change in eating, from a natural physiological response to hunger/satiety to a disturbed state that can be defined as a medical condition with possible lifelong consequences. Although many times, such disturbing states reach their peak presentation during adolescence and may cause significant health problems for the affected individuals, they may yet not meet the diagnostic criteria for a clinical diagnosis of eating disorder [6, 7].
Eating disorder (ED), as explained extensively elsewhere in this book, refers to a wide range of disturbances in eating and feeding that may vary in their nature, severity, or frequency over the lifespan. In the “Diagnostic and Statistical Manual of Mental Disorders,” fifth edition (DSM-V) [8], eating disorders are defined as conditions “
Prevalence, demographics, etiology, and comorbidities in ED are discussed elsewhere in this book and will not be included here. Instead, in this chapter, the author will try to shift readers’ attention from ED to a set of similar presentations under an umbrella term, disordered eating (DE) that due to an array of reasons may go unnoticed by clinicians but is nevertheless associated with several biopsychosocial complications.
As an introduction to the subject, the author will first define DE with special attention paid to its common features with ED, before moving on to give a summarized account on prevalence, comorbidities, and burden of disease in DE, followed by a section on etiology on DE, with focus on the importance of societal weight and body ideals, which together with a digitized modern world with an exponential increase in exposure to images portraying such ideals, seem to have created a healthcare dilemma where individuals are advised to maintain a healthy weight, but repeatedly fail to attain societal body ideals that are not necessarily in line with the definition of healthy weight. Treatment in DE follows the same principles employed in treating ED, which is covered in other book chapters and will not be covered here.
Please note in this chapter, the terms ED and DE are not used interchangeably. The term “eating pathology” is used where the author refers to symptom(s) shared between ED and DE.
2. Definition and diagnosis in disordered eating
Over the lifespan of affected individuals, clinical presentations of ED may greatly fluctuate, for instance from anorexia nervosa (AN) to much milder conditions where a diagnosis of ED would no longer apply [9]. Current classification systems, such as the latest edition of WHO’s classification system for mental and behavioral disorders, ICD-11 [10], and DSM-V [8], do not match the observed scope of eating problems and their related traits in general adolescent populations, resulting in a considerable proportion of adolescents with an array of eating problems left out with no treatment available to them [11]. On the other hand, heterogeneity, both within and across different subtypes of ED, makes conducting research on ED more challenging and less generalizable, hence the introduction of the umbrella term, disordered eating [12, 13].
Similar to eating disorders, DE is manifested through symptoms such as individuals’ concern about their body weight and shape, excessive or unnecessary use of weight reduction methods such as dieting or exercise, self-induced vomiting, inappropriate use of laxative or diuretic, or in some cases periodic binge eating, under- or overweight [14, 15].
Like eating disorders, DE has been associated with varying factors such as “biological” (BMI, puberty), “sociocultural” (socioeconomic status and exposure to media pressure), and “psychological” (early life adverse events, concerns about the body image, self-esteem, and negative affect) [16]. Interestingly, subthreshold symptom constellations observed in DE are associated with similar levels of functional impairment and emotional distress seen in ED [17, 18]. Recognition of impaired function in adolescents with DE is important since, many times, what brings a person to a clinician is their lack of function and not the mere presence or absence of certain symptoms directly taken from medical textbooks.
In clinical settings, the diagnosis of ED is made based on comprehensive clinical interviews and tests, which is a usually lengthy process that requires good training [19, 20]. Self-reported questionnaires [21] are used with the advantage of being quicker and easier to administer than semi-structured diagnostic clinical interviews [19, 22]. One other advantage of self-reported questionnaires is their more accurate reporting of symptoms, such as binge eating, when compared to clinical interviews [19]. Validation studies of self-reported questionnaires in adolescents have shown mixed results, and they are rendered less suitable for screening of eating pathology in overweight adolescents [22, 23].
Attempts have been previously made at making a more robust identification of DE by researchers [11, 22], by using standard screening tools available for ED [23, 24]. These tools are developed on the basis of observations of individuals with more severe presentations than those observed in general populations [25], and they neither seem to have sufficient reliability in the identification of earlier manifestations of ED nor are they fully suitable for the detection of disordered eating [25]. Generally, diagnostic thresholds for DE are either set lower than that for ED, or only a subset of ED symptoms are included in the screening process.
It is important to point out that currently, neither the definition nor identification of DE is fully agreed upon by the scientific community. The author is of the opinion that further identification of more reliable and validated screening tools for DE is important considering that 1 – prevalence of DE is higher than ED [13, 16, 26, 27, 28]; 2 – shared symptomatology between ED and DE makes studying the symptoms on their own of value and relevance to a wider group of individuals, independent of their diagnoses; and 3 – a sound understanding of factors attributing to the emergence of symptoms in DE seems pertinent for their prevention. Furthermore, given time, a proportion of adolescents with DE may evolve eating disorders, which makes the development of reliable identification tools for early detection of DE even more important [29].
3. Prevalence and demography in disordered eating
As mentioned earlier, ED and DE have a set of shared symptoms. Previous studies have shown that these symptoms seem to occur worldwide and across many ethnical, racial, and socioeconomic strata [30, 31, 32]. Prevalence of these symptoms is reportedly higher than that of clinically diagnosed cases of EDs [31, 33, 34]. Binge eating, purging, and dieting are present across adolescence and adulthood [26, 35, 36, 37]. Compared to extreme weight loss or fasting in adolescents that are more commonly flagged up to healthcare services, some prevalent and potentially harmful symptoms such as frequent binge eating and purging may go unreported and hence untreated [16], inadvertently also in populations with DE.
Existing scientific literature has shown that only a small proportion of individuals with ED come to the clinicians’ attention [38, 39] partly due to the vigorous application of current diagnostic criteria for ED [39, 40]. On the other hand, the validity of many epidemiological studies on ED has been scrutinized by the scientific community due to their selection bias for younger and fit female populations [38]. This makes research findings derived from clinical populations with ED less generalizable to the general population where targeted preventive methods are meant to be applied [38]. For similar reasons, DE in male adolescents is still understudied [41, 42], hence it is important to have a fresh look at symptoms in a population representing samples, rather than a sole focus on groups with evident clinical diagnoses of ED that have female over-representation.
Although compared to eating disorders, DE is generally milder in its symptomatology, it is more common amongst adolescents than ED [13, 16, 26, 27, 28, 43], especially amongst adolescents with higher BMI [44], making DE easier to identify and research in population-based studies.
Similar to ED [19], the symptom constellation in DE may vary based on gender [11]. Both ED and DE are generally more common in females than males [16, 26, 43], but one needs to also bear in mind that 25–30% of preadolescents who attend special ED clinics in Australia and UK are younger males [16, 26]. Moreover, prevalence of binge eating disorder, a subtype of ED with overlapping symptoms with DE, is equal in females and males [45].
4. Comorbidities and burden of disease
The burden of disease in eating pathology remains relatively high since it is associated with poor physical, poorer social relationships and quality of life, lower productivity, higher rates of substance use, anxiety, and depression, as well as increased self-harming behavior, suicidal ideation, suicidal attempts, suicide, and higher mortality [46, 47, 48, 49, 50, 51, 52, 53]. Adolescents with overweight, obesity, or those who are unhappy with their weight or shape also show an increase in mental distress. These incremental risks were observed independent of sex, age, BMI, and socioeconomic status, but adolescent boys with DE showed a stronger vulnerability to mental distress [11, 43].
Studies of temporal trends in the burden of disease have shown a considerable increase in the prevalence of binge eating and extreme dieting. Current scientific literature points at a considerable proportion of youth in the USA and Canada reporting high levels of functional impairment due to their attitudes toward eating [7, 27, 38].
Eating pathology may be associated with poor concentration and decision making, as well as with rigidity in thoughts, hence may reducing individuals’ mental capacity to recognize their problems or consent to necessary treatments [16]. Lack of timely and effective interventions for EDs can have devastating effects on the lives of sufferers, their families, and wider society. Early detection and timely intervention for eating pathology are vital considering the early age of onset, which is reportedly as low as 10 years old [54], and their possible debilitating effects on the physical and mental wellbeing that can pave the way for a range of unwanted long-term effects. Previous research suggests that increasing treatment coverage could substantially reduce ED-related mortality [32].
5. Etiology in disordered eating
Much of what is known about etiology in DE stems from studies done on symptoms of ED, as previously discussed in this book. The etiology of DE has been difficult to study partially due to its fluctuating and chronic course, and in parts because of its several biopsychosocial determinants. The issues surrounding etiological studies in DE are further complicated by the lack of consensus as how to define DE or classify its subtypes.
The symptom constellation in DE constitutes a range of areas; such as altered perception of weight or body size, negative emotion, changed cognition and behavior such as purging, dieting, extreme or unnecessary exercise, use of diuretics or anabolic steroids as seen in binge eating [8]. Human perception, emotion, cognition, and behavior are shaped and governed by a set of mechanisms that are themselves regulated by the combined effects of genetic and environmental factors, as well as by epigenetics [55, 56, 57]. The following subsections briefly look at these factors amongst adolescents with DE, before moving on to expand on the body ideals.
5.1 Genetic factors associated with disordered eating
Identification of heritable patterns in developing DE is important for designing interventions that can detect or modify DE presentations in affected persons, some of whom may develop ED later on in life or see similar presentations in their offspring.
There is a sound scientific ground for generating hypotheses on whether eating pathology, be it a part of ED or DE, shares biopsychosocial determinants with other prevalent public health issues, such as overweight/obesity. Abnormal weight and DE seem to share more than just their phenotypic traits. Family, twin, and adoption studies provide some evidence in favor of a set of common predisposing factors that regulate satiety, appetite, and reward systems in the human brain in both eating pathology and under- or overweight [58, 59, 60, 61, 62, 63, 64, 65, 66], for example, through the involvement of dopaminergic and opioid neurotransmitters [67]. A notable observation is the shared genetic susceptibility (FTO, MC4R, BDNF [63, 64], and OPRD1 [28, 60, 65]) between obesity and mechanisms underlying eating pathology. Synaptic plasticity and glutamate receptor activity are pathways that respond to the changes in feeding pattern, such as fasting. Interestingly, these pathways seem to be regulated by obesity-related molecules such as BDNF and MC4R [63, 68, 69, 70, 71].
Inheritance studies on subtypes of ED, such as anorexia nervosa, have not identified a single gene with a large effect [72, 73, 74, 75, 76]. When no single genetic marker shows a significant effect on the existence of a trait, genetic risk scores (GRSs) have been instead used to study a possible additive effect of several genes on that trait [77]. GRSs have been useful in the identification of shared underlying mechanisms between eating behavior, obesity, ED [78, 79], and satiety [80]. Likewise, GRSs have been used in studying inheritance amongst sex-stratified populations of adolescents with DE [11] where results showed an association between obesity-related genes and DE, as well as observing sex-specific differences in how genes seem to associate with DE symptoms. However, in the absence of a clearer classification of DE symptoms and larger genetic studies, drawing further conclusions on this matter seems premature. Whether these risk factors aggregate in families of individuals with DE is not yet fully understood and needs further research.
5.2 Other factors associated with disordered eating
Investigating the collective effect of biopsychosocial factors in DE at the adolescent age is important since it can help identify individuals at higher risk for developing negative long-term health consequences of eating pathology.
5.2.1 Psychiatric comorbidities
There are reports on a link between negative emotion and regulatory systems involved in food intake [61]. Comorbidity between eating pathology and a wide range of mental disorders, such as anxiety, depression, substance misuse, and personality disorders, is well documented [81, 82, 83, 84, 85, 86, 87, 88]. Early life adversities, such as childhood neglect and physical and sexual abuse, have significantly higher prevalence amongst adolescents with eating pathology [35].
5.2.2 Overweight and obesity
Obesity is recognized as a major health problem across the world, also amongst adolescents [89, 90]. In the past few decades, human lifestyle, eating habits, and physical activity together with a subsequent imbalance between food consumption and energy expenditure have undergone major changes [91]. Overweight and obesity have overarching unwanted, yet preventable consequences for both physical and mental health across the lifespan [92]. Like ED and DE, abnormal weight can impair both physical and mental health [92, 93].
The association between weight status, eating pathology and other psychiatric disorders is complex. Both unhealthy weight change and ED are, as shown in animal models, associated with some degree of altered food consumption or absorption [94]. On the other hand, change in eating style has been associated with being overweight or obese, ED, and depressed mood, pointing to the possible association between eating pathology and psychiatric disorders [95]. Moreover, both abnormal weight and ED have a higher prevalence of clinical depression [96, 97], anxiety [98, 99], bipolar affective disorder [100, 101], and substance use disorders [102, 103]. Interestingly, some weight-loss treatment regimens are also known to help improve psychosocial outcomes in obese children with disordered eating [104, 105]. A recent systematic review has shown that the link between obesity and ED is stronger than the link between obesity and depression, anxiety, or substance use disorder [106].
Overweight and obesity were more prevalent in adolescents with DE who show patterns of uncontrolled appetite/overeating compared to those who have poor appetite/undereating. Underweight seems to be more prevalent in adolescents with DE and poor appetite/undereating compared to those who show uncontrolled appetite/overeating [11].
However, it is interesting that despite ample scientific evidence for a close link between abnormal weight and eating pathology, having abnormal weight is not a necessary diagnostic criterion for any ED, or for that matter DE, other than in anorexia nervosa (AN). Neither it is necessary for an individual with abnormal weight to have suffered from any form of DE.
National percentile growth charts show the spread of distribution of weight by height, weight by age, and height by age in a given population of a certain age, gender, and race [107] and are widely used as an indicator of physical development and health from infancy throughout adolescence. Body mass index (BMI), another measure of weight status, has also been used to categorize individuals into underweight, normal weight, overweight, or obese groups [108]. BMI, as originally called Quetelet’s Index (QI) [109], is a value derived by quantification of the proportion of mass to height in each individual and is calculated by dividing the body weight in kilograms to the square of the body height in meters (kg/m2). Use of BMI as an indicator for eating pathology can be particularly misleading amongst adolescent males who may, due to higher muscular volumes and intake of certain supplementary nutrients, have normal BMI even in more debilitating instances of eating pathology.
5.2.3 Societal body ideals
It is also vital to study disordered eating in the context of increasingly more appearance-focused societies, keeping in mind the possible negative effects of unattainable societal body ideals on younger individuals during their formative adolescent years. Societal emphasis on physical appearance may put pressure on adolescents to attain or maintain a certain body type, the so-called body ideals. Many adolescents try to achieve their body ideals by restricting the frequency or content of what they eat, or by vigorous physical exercise, which at times comes at the cost of them neglecting their other needs. Societal stigma about having an eating pathology may prevent adolescents from reporting their problems [110]. It is difficult to identify and costly to treat eating pathology, in part due to a lack of subjective insight into ill-fated consequences of unreported or untreated eating pathology [110, 111].
Body image, a subjective perception of the human body, is a complex construct based on comparisons made between the perception of an individual’s body size or shape to that of others. “Size,” the magnitude or dimension of a thing, is determined by comparisons drawn between various objects on their magnitude of a quantity, such as mass and length, which could then be expressed either relative to a measuring unit or by assigning adjectives such as smaller/bigger or heavier/smaller.
Mass, weight, or length are separate concepts. In physics, mass is loosely referred to by the amount of “matter” in any given object. Weight, however, refers to something different and more dynamic than the fixed amount of matter in a mass at any given time. Weight is the force that is “experienced” by an object due to gravity. Hence, body image may be considered both “relative” and “subjective,” as it may also be dynamic and seen as “amenable to change” [112]. However, human body image seems to be a more complex concept than only a mental picture of dimensions, but rather a multifaceted construct made of neurological, psychological, and sociocultural elements [113].
First scientific studies of body image date back to the 1900s and emerging clinical reports of altered body perception after brain injury in the parietal lobe or phantom limb in amputees. Krueger thought of body image as the representation of identity derived from internal and external body experiences [114]. Schilder attempted at defining body image by combining known concepts of the “somatopsyche,” postural model of the body, and the more recent Freudian understanding of ego [113]. In his book, “The Image and Appearance of the Human Body,” Schilder suggested that body image plays a fundamental role in individuals’ relation to themselves, to their fellow human beings, and to the world around them [113].
Body image is dynamic and may change with individuals’ age, mood, or even type of clothing. People with the same body size might have different body weights due to differences in their body composition or muscular and bone density [56, 115]. Discrepancy between subjective body image and actual body size is common in the general population and is a shared feature in many conditions, such as body dysmorphic disorder, obesity, or some types of ED [6]. Besides, human perception is not just a passive reception of sensory information but is also formed by the percipient’s cognition that in turn is dependent upon learning, memory, and attention, as well as on pre-learned concepts or expectations (body ideals) [116, 117].
Mismatch between body image and body ideals may lead to unnecessary concern. Concerns about weight or body size are present in various subtypes of ED [8]. Being dissatisfied with one’s body is known to associate with changes in affect, lower self-esteem, and social dysfunction [118]. Interestingly, weight underestimation has been associated with less symptoms of anxiety/depression in both adulthood [119] and preadulthood [120].
Individuals with weight or body size concerns may unnecessarily resort to ways to change their appearances, such as dieting or exercise. Many dieting regimes are advertised and endorsed by the society as effective ways to “look better,” despite, at times, their questionable effectivity. Subjective body dissatisfaction arising from discrepancy between one’s body image and body ideals, combined with individuals’ perceived inability to change their appearance by dieting or exercise, can cause or worsen mental distress and may lead to other negative health outcomes [121].
Considering selective mechanisms such as “attention” also influence human perception [122], one can postulate whether focus on body size, may by itself, shape as well as distort, individuals’ body image, alter their behavior (dieting) or even mental state.
Societal body ideals are gender based [119], which makes it interesting to examine gender differences in exhibiting weight concern, body size perception, and mental distress. It is also tempting to postulate that pre-learned expectations of how a body should look like (body ideals), as represented in visual clues available through social media or fashion industry, can hypothetically affect individuals’ body image.
Association studies between adolescents’ BMI, weight concern, body size perception, or dieting and their mental health have provided some answers to these questions [43]. For example, having weight concern has been associated with increased odds of mental distress amongst adolescent boys and girls, to a greater degree than actually being overweight/obese. Similarly, body size overestimation at adolescence has shown a greater impact on mental distress amongst adolescents, than weight concern. Male adolescents who overestimate their body size were shown to be at particularly high risk for having mental distress, compared to their female counterparts [43].
6. Conclusions
Disordered eating at adolescence is prevalent but understudied. The importance of research in the field, especially amongst adolescent males, cannot be overemphasized as these adolescents may suffer from both physical and psychiatric consequences of their eating pathology.
The underlying molecular biology in disordered eating is still understudied. Genetics cannot fully explain the variation in the formation, severity, and course of disordered eating amongst individuals with similar faulty genes. The use of the polygenetic risk score (PRS) in future genetic studies may help quantify the actual genetic risk in each individual carrying these faulty genes.
Furthermore, variation in individuals’ response to standard medical and nonmedical interventions for disorders of feeding and eating underscores the importance of taking a holistic approach to studying the combined effect of genetic and environmental factors. Epigenetic studies can shed light on resilience factors that may protect young adolescents against developing disordered eating in the first place. Besides, by identification of environmental factors that act as trigger for developing disordered eating, epigenetic studies can help introduce timely and appropriate preventive measures in young adolescents.
Likewise, developing novel intervention methods that can address both disordered eating and comorbid disorders requires studying these disorders together. However, relative lower prevalence of some forms of ED would translate to fewer potential research participants from clinical settings where treatment is sanctioned for more severely affected individuals. Whilst international consortia and multicenter studies are useful ways to overcome this problem, they may introduce other issues such as heterogeneity in study population that may potentially affect study findings and their interpretations.
Future longitudinal studies that focus on traits rather than clinical diagnoses may offer a methodological solution by increasing the number of research participants in any given category of ED symptoms and traits. Findings of population-based studies are more generalizable to nonclinical populations and may better help design preventive measures that fit young adolescents who have not yet reached the disease threshold.
Scientific literature provides evidence for the relative importance of subjective weight concern, rather than being overweight/obese in adolescent mental health. Body size overestimation is associated with mental distress, especially in boys. Body size overestimation and weight concern seemed associated with mental distress, the former playing a greater part. Body size overestimation may be related to increasingly unattainable societal body ideals. Lack of effective weight control methods combined with easy access to relatively cheaper fattening food and overeating has led to an increase in overweight as well as dissatisfaction with own body. The use of compensatory weight reduction behaviors, such as dieting, extreme exercise, and use of anabolic steroids, has also been on the rise amongst adolescents. A change of societal body ideals to a set of more attainable and population representative size or shape may help prevent negative consequences of unnecessary weight concerns or dieting.
Despite showing higher mental health vulnerabilities, male adolescents with DE are an overlooked group. A more thorough examination of DE traits in formative adolescent age is necessary for the early identification of vulnerable adolescents.
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