**1. Introduction**

Mental health problems have increased, especially among young people, over the last decade [1]. The most common mental problems are behavioural, emotional, and hyperkinetic disorders. Among these illnesses, disordered eating behaviours are rapidly increasing in a short time, especially among young women [2,3]. These disordered attitudes are defined as afflictions in which people suffer severe disruption in their eating behaviours, thoughts and emotions. The people who suffer from these complaints are usually preoccupied with food and weight. In this sense, disordered eating is used to describe a range of irregular eating behaviours that may or may not warrant a diagnosis of a specific disordered eating attitude [4].

These disorders usually occur in women in their twenties or during adolescence [3]. People who su ffer these disorders usually present altered attitudes, behaviours, weight perception and physical appearance [5]. Moreover, disordered eating behaviours or attitudes are defined as unhealthy or maladaptive eating behaviours, such as restricting or binging and/or purging [6]. These behaviours are not categorized as an eating disorder, though they are considered a phase of diagnosed eating disorders [7].

The concern from health care systems is based on the fact that these severe mental disorders usually puts in danger the well-being and health of the people who su ffer them [5]. One-third of the women in the world have su ffered from these mental problems at some point in their life [6]. If they are inadequately treated, they may develop severe clinical disorders [8]. Moreover, around 1% of the people with these disordered eating attitudes struggle with unhealthy and emotional problems through all their lives [6].

Out of the population with disordered eating attitudes, 16% of them present overeating, 20% purged by vomiting, and 61% food restraining [9]. These frequencies changed as people aged, with food restriction being more common in older women and vomiting during adolescence [10]. Moreover, recent data have discussed the increase of how the minimum age of the people with disorders is around 12 years of age and decreasing. Meanwhile, the prevalence of disordered eating attitudes appears to increase as young adults or adolescents grow older [10].

Although these diseases have a crucial psychobiological component, social and cultural factors have a significant influence. Among these factors, advertising has been described as an internalizing or normalizing means to spread unrealistic beauty ideals. Therefore, a higher incidence of these diseases is presented in advanced and modern societies and people with the best living conditions, mostly caused by the popularization of thin and muscular ideals [11–13].

Several biological factors have been linked to disordered eating attitudes, with up to 50% of disordered eating being described as familiarly transmitted [5,14]. Researchers have also suggested that neurotransmitters in the brain are involved in disordered eating attitudes and, therefore, eating disorders [15,16]. Additionally, the hormones have been linked as factors to puberty, body perception and body concerns [17,18]. Testosterone is included among those hormones highly studied, with blood samples providing a more precise method of examination. Nevertheless, di fferent researchers pointed out the possibility of using indirect markers to avoid taking biological samples and creating risks for the participants. In this sense, most studies have linked testosterone and estrogenic levels via the 2D:4D digital ratio as an indirect indicator [19], which heavily dictates attractiveness [17]. This ratio, which is based on the di fference in length of the phalanges of the hands (2D:4D ratio) having a lower ratio as an indicator of the existence of a higher level of testosterone, is used for the determination of intrauterine testosterone levels during gestation [20]. This ratio has reflected the relationship with self-perception, body image, body dissatisfaction, and disordered eating behaviours [20,21]. Based on these studies, the hormone levels, and the indirect marker, might appear to have essential roles in disordered eating attitudes [22]. Nevertheless, other authors have described how biological or genetic factors are essential, but may not determine, these disordered eating attitudes [23].

Other factors, such as ethical or familiar factors, contribute to the development of this disordered eating behaviours [24]. In this sense, previous studies have established that the probability of developing a disordered eating attitude or a diagnosis of eating disorders is higher if the mother had a disordered eating or self-esteem problems [25,26]. Moreover, ethnicity has been linked to the perception of beauty ideals, self-esteem and body perception [27,28].

Another critical factor is the media by which beauty ideals have been promoted. The media plays a vital role in formulating what is attractive in society, increasing the thin beauty ideal among females being unattainable [29,30]. These ideals confirmed the way young people perceived themselves and, therefore, how they value themselves [10,31]. This contradiction between what society portrays as a role model and the real body that many young women have has resulted in body concerns. Body concerns usually maintain over time and increase body dissatisfaction. This body dissatisfaction emerges because of the distortion on the body image, its perception and, therefore, body concern [32,33]. This dissatisfaction also plays an essential role in disordered eating attitudes since it provokes emotional and psychological distress [34].

In this sense, the theory of social comparison and numerous studies have studied the relationship between body dissatisfaction and disordered eating attitudes to better understand the causes of these illnesses. These previous works showed that real comparisons with other people leads to a distortion of body image and may favour disorderly feeding [11,29,35]. Additionally, Fredrickson and Roberts (1997) suggested that sexualization and self-objectification promoted via media should be considered as a risk factor for disordered eating attitudes [36–38]. Based on previous and recent studies it seems that the role of the media in disordered eating attitudes is noteworthy [1,11,39].

This paper presents a research study in which these objectives have been pursued: first, to determine the relationship between disordered eating attitudes in female university students and sociocultural factors, such as the use of social network sites, beauty ideals, body satisfaction, the body image and the body image desired to achieve. Second, to determine whether there is a sensitive relationship between disordered eating attitudes, addiction to social networks, and other biological factors, such as testosterone levels.
