Introduction

In some cases, self-imposed dietary rules intended to promote health generate detrimental consequences on health, as stated in 1997 by Steven Bratman [1]. The pursuit of an “extreme dietary purity” due to an exaggerated focus on food may lead to a disordered eating behavior called “orthorexia nervosa”.

Orthorexia is a neologism coined from the Greek (ὀρθός, right and ὄρεξις, appetite). The term means ‘correct appetite’. Conversely, orthorexia nervosa (ON) is an expression created to indicate a possible new eating disorder whose core symptom is an obsessive and unsafe focus on eating foods perceived as healthy.

A growing number of articles in literature refer to ‘orthorexia’ as a keyword, and an increasing number of published articles have been observed throughout the last years [2, 3].

However, at present there is no universally shared definition of ON, the diagnostic criteria are under debate, and the psychometric instruments used in the literature (mainly the Orthorexia Self-Test commonly called Bratman Orthorexia Test (BOT) [4] and the ORTO-15 [5]) revealed some methodological flaws [6].

Two key features should be present among the diagnostic criteria of ON:

  1. (a)

    obsessive focus on dietary practices believed to promote optimum well-being through healthy eating (with inflexible dietary rules, recurrent and persistent preoccupations related to food, compulsive behaviors);

  2. (b)

    consequent, clinically significant, impairment (e.g. medical or psychological complications, great distress, and/or impairment in important areas of functioning) [7].

As the theoretical discussion continues, other issues need to be analyzed, such as possible body image disturbances, weight concerns, and degree of insight [2].

Therefore, it is necessary to reach a consensus on the definition of ON, to validate new assessment instruments, and to distinguish different severity levels [8]. For this reason, the Orthorexia Nervosa Task Force (ON-TF) was established in 2016. ON-TF includes researchers from many countries actively dealing with ON.Footnote 1 It pursues seven specific aims:

  1. 1.

    To outline a definition and reliable diagnostic criteria for ON.

  2. 2.

    To describe, according to the available literature ON development and course, risk and prognostic factors, diagnostic issues related to gender or cultural aspects, diagnostic markers, comorbidity (clinical, functional and psychological consequences), and differential diagnosis.

  3. 3.

    To verify in which DSM category ON would best fit.

  4. 4.

    To develop qualitative research through well-designed case studies.

  5. 5.

    To validate a new self-administered questionnaire, starting from ORTO-15, Bratman’s Orthorexia Self-Test, and Dusseldorf Orthorexia Scale, and taking into account the new definition and diagnostic criteria.

  6. 6.

    To investigate ON prevalence according to the new shared diagnostic criteria in different countries and different samples (age classes, gender, social and cultural context, athletes, etc.);

  7. 7.

    To evaluate medical and psychiatric comorbidities.

The article performs a preliminary narrative review of the literature to assess state of the art in ON definition, diagnostic criteria and related psychometric instruments.

Methods

The authors collected articles through a search into Pubmed/Medline, Scopus, Embase and Google Scholar (last access on 07 August 2018), using “orthorexia”, “orthorexia nervosa” and “obsessive healthy eating” as search terms and filled three tables (Tables 1, 2, 3) including narrative articles (English), clinical trials (English), and articles in languages different from English.

Table 1 Studies on orthorexia nervosa: reviews, letters, commentaries, editorials, case reports
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Table 2 Studies on orthorexia nervosa with non-clinical and clinical samples
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Table 3 Studies on orthorexia in languages different from English
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For each paper, we defined type of the study, characteristics of the sample, definition of ON, diagnostic criteria, psychometric tests and conclusion/result.

For each abstract, the full text was retrieved for the evaluation. The data extrapolated from the revised studies were collected in tables that summarize study design and methods, describe the sample, give background information, and present results, allowing the reader to identify important information easily. In particular, for each study the following data were extracted: author, year of publication, general characteristics of the population enrolled, study design, possible diagnostic criteria for ON, psychometric instruments, main results and conclusions (Tables 1, 2, 3). The first draft was reviewed and enhanced by all the co-authors.

Results

The literature search retrieved 141 articles, published up to 2018. Among these articles, 34 are reviews, letters, commentaries, editorial and case reports; 73 are studies with clinical and non-clinical samples; 24 are articles published in a language other than English. All of them were summarized, and the main characteristics and results are reported in Tables 1, 2 and 3 [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133].

Table 4 synopsizes the diagnostic criteria for ON proposed in four papers.

Table 4 Detailed classification criteria for ON delineated by some scholars (and presented in the latest research)
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Most of these papers were research articles aimed at the evaluation of the prevalence of ON or at the definition of certain characteristics (gender, age, BMI, social/educational status, eating behavior) or psychological profile (self-esteem, narcissism, perfectionism, previous history of eating disorders, overweight and appearance preoccupation). It is hard to compare most results for the lack of a shared definition of ON, standard diagnostic criteria, and reliable psychometric instruments.

  • Definition of ON:

The terms used by the different authors concerning the feelings accompanying the search for food were fixation, obsession and concern/preoccupation on food quality/healthy eating.

These terms were moreover emphasized through different adjectives: obsessive, exaggerated/excessive, unhealthy, compulsive, pathological, rigid/controlling, extreme, monoideistic, maniacal, time-consuming, and overwhelming.

The suitable food was mostly identified as healthy/proper/correct, sometimes organic, (biologically) pure, safe, while the harmful aspect of food was defined as unhealthy, more rarely impure or related to “food production”.

The diet or eating habits are usually defined as restrictive, seldom also as ritualised, strictly controlled, selective food avoidance, and distorted; the risk and consequences on the individual nutrition status and well-being are referred to as shortage of essential nutrients, malnutrition and underweight, changes in social relationships because of the constant thought on healthy food.

  • Diagnostic criteria:

Most of the papers did not define the diagnostic criteria.

DSM (edition IV or 5) criteria for anorexia nervosa (AN), or avoidant/restrictive food intake disorder (ARFID), or body dysmorphic disorder (BDD), were adapted for ON in 13 studies.

Specific diagnostic criteria proposed by the authors were used in few studies (Tables 1, 2, 3).

Four of them [7, 27, 96, 134] published their proposal, allowing a brief comparison of criteria suggested to diagnose ON (Table 4). All these studies indicated as primary diagnostic criteria: (a) obsessional or pathological preoccupation with healthy nutrition; (b) emotional consequences (e.g. distress, anxieties) of non-adherence to self-imposed nutritional rules; (c) psychosocial impairments in relevant areas of life as well as malnutrition and weight loss.

Besides rigid avoidance of food considered unhealthy, the presence of positive effects due to compliance with self-defined healthy eating behavior was indicated as a criterion for diagnosis [7].

Two proposals [27, 134] additionally mentioned the presence of overvalued ideas as a criterion, while Dunn et al. [7] described compulsive behavior as crucial.

All proposals also included criteria for a differential diagnosis. While Dunn et al. [7] and Barthels et al. [64] only mentioned that the desire for weight loss must be absent, Moroze et al. [38] and Setnick [65] specified additional criteria, e.g. the absence of an obsessive–compulsive disorder and psychotic disorders.

Additionally, each set specified some unique criteria or aspects not used by the others. Barthels et al. [27] affirmed that insight is not a necessary criterion. Dunn et al. [7] proposed that an escalation of dietary restrictions over time should be used as a criterion. Moroze et al. [96] proposed spending excessive amounts of time and money as criteria. Setnick [134] added as a criterion of exclusion that eating behavior should not be the result of a lack of available food or culturally sanctioned practice.

  • Psychometric tests:

ORTO-15 was the most used psychometric tool (49 studies) with different versions (translated and validated in various languages, integral or short version). The Orthorexia Self-Test developed by Bratman (BOT) was used in nine studies, the Dusseldorfer Orthorexie Skala (DOS) in five studies [21, 22, 51, 86, 115] and the Eating Habits Questionnaire (EHQ) in five studies [65, 101,102,103]. Finally, Olejniczak et al. [104] used a new questionnaire while Varga et al. [130] added to the ORTO-15 different items, developed for the 2014 study.

Discussion

The present review synopsizes the literature based on the definition of ON, proposed diagnostic criteria and psychometric instruments used to assess orthorexic attitudes and behaviors. This work represents a necessary starting point to allow a further progression of the studies on the possible new syndrome and to overcome the criticisms that have affected both research and clinical activity.

The results show a considerable variety of answers to the three core issues.

Definition

ON was defined in the different papers with three/four terms: obsession (the most frequent), fixation, and concern/preoccupation. Obsession indicates a persistent and disturbing thought, while fixation is a stereotyped behavior related to an obsessive and unhealthy preoccupation or attachment. Concern refers to an uneasy state of blended interest, uncertainty, and apprehension while preoccupation may be considered a synonym of concern with probably a higher degree of alarm representing a state in which someone gives all his/her attention to something (https://www.merriam-webster.com/dictionary/). The three/four terms seem, therefore, to be complementary since they look to different aspects and moments of the same problem: the concern about healthy diet leads to having all the attention captured by food (preoccupation), thus evolving to a persistent and disturbing thought (obsession) and a stereotyped behavior (fixation).

These terms were moreover emphasized through different adjectives defining diverse aspects of the behavior from a quantitative point of view (exaggerated/excessive, extreme, overwhelming, time consuming) and a qualitative perspective. This latter was further outlined considering clinical (unhealthy, pathological) and psychological (rigid, compulsive, maniacal, monoideistic) characteristics. The three aspects of the definition and the two/three groups of terms used to define the essential feature of ON better need to be encompassed in the definition that the ON-TF will endorse.

As to eating behavior, the suitable food was identified with different levels of quality. In most papers, it was defined in a generic and sometimes opposite way: healthy/proper/correct/safe or unhealthy, depending on the point of view of the authors. In other studies, the definition considered specific aspects (organic, (biologically) pure, or related to food production). Last, in some cases, the definition of healthy food seems not to refer to the biological quality but to pseudo-moral aspects (two studies used the term impure).

The diet followed by subjects with ON was also defined looking at different characteristics referring to dietetic (restrictive, characterized by the avoidance of certain foods, distorted eating habits, shortage of essential nutrients, leading to malnutrition and underweight) or behavioral aspects (ritualised, strictly controlled, becoming the central focus of life, with modification of social relationships).

Diagnostic criteria

An official set of diagnostic criteria does not yet exist. Four authors proposed formal diagnostic criteria and, in some cases, used the DSM (IV or 5) classification and tried to adapt to ON the criteria employed for AN, ARFID or BDD. The debate is ongoing in the literature to decide whether ON should be considered as a distinct disorder, a variant of an existing eating disorder or an obsessive compulsive disorder or finally (just) a disturbed eating habit [36].

Defining the boundaries of ON concept of ON and verifying which elements (e.g. eating behavior, compulsivity, body image disturbance, body weight concerns, insight, medical complications, psychosocial functioning) need to be considered in its definition, is a ON-TF mission. The consistency of some of the proposed criteria provides a useful starting point to develop diagnostic criteria further and, if necessary, modify them and add criteria only mentioned by one or two authors to find a reasonable consensus.

Psychometric instruments

The ORTO-15 (including its versions with a reduced number of items) and the Orthorexia Self-Test were the most used psychometric tools. They both present significant psychometric flaws, and one of the aims of the ON-TF is the validation of a new self-administered questionnaire taking into account a new shared definition and new shared diagnostic criteria for ON.

As Missbach et al. [8] correctly stated, an instrument aimed at assessing behavioral traits should be consistent and reliable across different population groups (also reflecting cultural and religious backgrounds) and consider the essential features that describe a disorder (e.g. ON).

One of the most important challenges is to draw a boundary between adopting a healthy diet—which is recommended to everybody to prevent “hidden” malnutrition and reduce morbidity and premature mortality—and developing inflexible beliefs, attitudes, and behaviors related to nutrition with unhealthy consequences.

Strengths and limitations

The present review considers studies on ON written in English and quoted in PubMed till 07 August 2018 and provides an updated reliable basis for analysis and constructive criticism for the reader offering research propositions and framework for future analysis.

The main limitation is linked to the same premise because the literature on ON is very heterogeneous and does not allow a review with meta-analysis.

Clinical considerations and outlook

Only significant distress, psychological and physical impairment may bring a person to seek treatment and, at present, individuals with clear ON symptoms are rarely observed in clinical practice. However, clinical experience and case reports suggest that ON [30, 105] and ON by proxy [3] can be distressing and harmful conditions.

From a psychodynamic point of view, individuals with ON symptoms often present personality problems. Perfectionism, rigidity, and difficulties in self-regulation, identity, self-esteem, emotional modulation, and impulse control may underlie the excessive focus on the healthy diet that, subsequently, affects social functioning and supports isolation. Table 5 summarizes differences and similarities with eating disorders and obsessive–compulsive disorders.

Table 5 Differences and similarities between orthorexia nervosa and eating disorders (a) or obsessive–compulsive disorders (b)
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A shared definition of ON with detailed diagnostic criteria will allow researchers to answer three fundamental questions:

  • Is ON a genuine new syndrome or a product of the contemporary diagnostic fad [127]?

  • Is ON a reliable, valid, and useful diagnostic category [135]?

  • If that is the case, in which group of mental disorders should ON be included? In particular, should it be classified among the eating disorders or the obsessive–compulsive disorders [36]?