This study was conducted in Poland and Spain between March and June 2021. After being fully informed of the purposes of the study and providing informed consent, participants were asked to complete an anonymous questionnaire. Inclusion criteria were the ability to read and write in Polish/Spanish, an age of 18 years or older, a gender identity as male, and a sexual orientation identity as gay/homosexual. The total final enrollment was 394 gay men (188 from Poland and 206 from Spain).
The call for this study was distributed via social media advertisements posted in groups for gay men on Facebook and other social media (Instagram, Twitter). In both Poland and Spain the survey was available via an online platform webankieta.pl  to obtain data and access control of the sample using IP filtering. The survey was started 436 times and completed by 394 participants (90%).
The data were collected using a three-section self-administered questionnaire. The first section contained questions pertaining to demographic data, such as age, sex, height, body weight, place of living, employment status, relationship status, educational level, eating pattern used, self-reported health assessment, use of Pre-Exposure Prophylaxis (PrEP), and use of social media and dating app (Grindr). The second part was the Polish and Spanish version of the ORTO-15 (Orthorexia Nervosa: ORTO-15). The third part was the Polish and Spanish version of the EAT-26 (Eating Attitudes Test EAT-26).
Eating disorders tools
The ORTO-15 questionnaire is a self-report 15-item measure with a 4-point Likert scale (always-often-sometimes-never) developed in 2004 by Donini and colleagues, modeled on the Bratman test. Is the most frequently used tool to assess severity of ON . In our study we used the Polish and Spanish validation versions of ORTO-15 [14, 15]. This questionnaire measures the interrelationship between cognitive-rational, clinical and emotional aspects of eating behavior . The ORTO-15 questionnaire assesses beliefs about attitudes covering food selection, the extent to which food concerns influence daily life, the perceived effects of eating healthy food, and habits of food consumption. Lower overall scores refer to more ON components (increased ON tendency). Cronbach's alpha is 0.80 (Spanish version) and 0.78 (Polish version) [13, 14]. Two cut-offs for ORTO-15 have been proposed: < 40 (sensitivity 100%, specificity 73.6%, positive predictive value 17.6%, negative predictive value 100%) and < 35 (sensitivity 86.5%, specificity 94.2%, negative predictive value 94.1%) . Other studies used median split to define individuals with or without ON tendencies . Since our study involved samples recruited in Poland and Spain, the cutoff of 35 was used to identify possible ON, as described in the literature. [16,17,18] (p26)
The Eating Attitude 26-item questionnaire (EAT-26) is divided into three subscales: Bulimia Nervosa, dieting behaviour, and food preoccupation . The questionnaire consists of 26 items, rated on a 6-point Likert scale (3 = Always, 2 = Usually, 1 = Often, 0 = Sometimes, 0 = Rarely, 0 = Never). Scores above 20 points indicate a real risk of EDs. Higher results obtained by the addition of all 26 scores indicate higher risks of developing eating disorders. In our sample we use a Polish and Spanish validated tools [20, 21]. This test is not a diagnostic tool, but some authors suggested that the EAT-26 might identify cases at risk for EDs in clinical spectrum .
This study was approved by the independent Bioethics Committee of the Wroclaw Medical University (decision no. 812/2020) and Committee on Ethics and Research Medicinal of La Rioja (decision no. CEImLAR P.I. 471). The study was carried out in accordance with the tenets of the Declaration of Helsinki and recommendations of good clinical practice. For reporting, the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines were followed . All participants gave their informed consent to participate in this study.
The mean, median, standard deviation and quartiles were calculated as a summary of the distribution of quantitative variables, while qualitative variables were summarised with absolute value and percentage. Logistic regression was used to analyse the impact of quantitative variables on the dichotomous outcome. Based on the simple regressions, variables were selected for inclusion in the multiple regression. Variables with the lowest p-values were chosen so that the EPV (Events Per Variable) index was at least 10 [23, 24]. A total of 13 variables were included in the final analysis. Odds ratios (OR) with 95% confidence intervals are shown. The two-sided P value < 0.05 was considered as significant, and statistical analysis was performed with R 4.1.2.