1. Introduction
Adolescence, the phase of life between childhood and adulthood, is traditionally considered as a healthy stage of life; however, it represents a vulnerable period for psychological, physical, and social outcomes [
1]. Adolescents experience rapid physical, cognitive, and psychosocial growth and these neurobiological changes predispose on the one hand to behavioral patterns, related to diet, substance abuse, and lifestyle habits, that can protect their health, but on the other hand, these same behaviours can represent risk factors and, in the medium and long-term future, disease. Generally, numerous variables essentially linked to lifestyle habits or social context protect or undermine adolescents’ health. Among the other factors influencing the perception of health and well-being, an important role is played by body weight and its perception, both in the case of underweight and overweight [
2,
3]. It is well recognized that overweight and obesity in adolescents are associated with an increased risk of psychological diseases, behavioral, social, and emotional problems, with consequent impairment of quality of life [
4]. Less evidence is present on the psychosocial effects of being underweight, although it seems to indicate internalizing problems, in particular depression and socially withdrawn behavior [
5]. However, underweight girls usually present a greater perception of well-being. This may contribute to the onset of eating disorders, characterized by altered self-esteem, body image, and social media use [
6,
7]. The body image (BI) construct, considered in recent years one of the most influential factors affecting psychosocial well-being [
8] is associated with body weight perception. This is because body image is composed of different facets, perceptual, affective, cognitive, and behavioural [
9]. Moreover, an altered body image is related to unhealthy weight control behaviors, lower levels of physical activity, and reduced social relationships [
10]. On the contrary, a proper body image has a protective role towards lifestyle habits and reduces the possibility of suffering from being underweight and overweight [
11].
Besides lifestyle habits, traditionally linked to diet and physical activity, the literature has made the effort to find other moderators in the body weight control, referring for instance to classic risk behavior, but the evidence is still fragmentary.
Thus, taking into account these aspects, the present study conducted on a sample of Italian late adolescents, has the following aims: first, we aimed to investigate health-related quality of life (HRQoL) dimensions associated to different BMI categories, both in general population and by sex. We hypothesized that underweight, overweight and obesity would show reduced HRQoL compared to normal weight counterpart. Second, we considered sex differences possibly involved in this relationship.
4. Discussion
This research aimed to determine the effects of belonging to a specific BMI category on health-related quality of life (HRQoL) on a sample of late adolescent students, taking into account sex differences. The main results of this study can be reassumed in the following points: i) the overweight and obesity category is predominantly expressed in the male population, while girls are more represented in the underweight category; ii) boys showed higher values of perceived well-being, better emotional state and self-perception, better family and school relationships, while females reported problematic use of social networks and a greater tendency for eating disorders.
When we consider BMI categories: i) a reduced perception of psychological well-being, self-perception, and fewer social relationships are found in the overweight and obese adolescent categories, while the underweight category is characterized by a better adherence to the Mediterranean diet and better perception of financial resources, especially in girls; ii) normal weight subjects exhibited a problematic use of social network, whereas eating disorders was more pronounced in underweight and obese adolescents.
Consistent with the literature, the present results provide clear evidence that overweight and obesity are more expressed in male population. This prevalence is usually more strong in high income and upper middle-income countries, were obesity is two-fold greater in boys than girls [
20]. This sex-difference may be due to biological influences. In fact, biological differences in body composition between sexes, already present during childhood, became more marked in adolescence by the role of sex hormones [
21,
22]. In fact, females have higher levels of circulating concentrations of leptin, responsible of an increased appetite suppression and promotion of energy utilization [
23]. Another possible explanation of sex differences in obesity would seem to be related to brown adipose tissue (BAT) whose decrease is implicated in the development of obesity [
24]. Although there is no clear evidence, some studies have found BAT to be predominant in girls than boys [
25]. Furthermore, it is important to emphasize that the number of school-aged adolescents with obesity is expecting to rise from 150 million worldwide to over 250 million by 2020, with an increase in the long-term of other related chronic disease, such as type 2 diabetes and cardiovascular disease [
20,
26]. This growing prevalence of obesity in adolescence globally is of major challenge, not only for the long-term effect, but also for the short health complications, including increased cardiovascular risk, disturbances of sex hormones, hepatic and orthopaedic problems [
27]. Although the physiological underlying mechanisms responsible of adolescence obesity rise are not yet fully understood, certainly adolescence is a time of rapid physical, social, and psychological development, and as a result, it offers multiple possibilities for unhealthy and/or risk behaviors. In this frame, psychological/mental health problems which emerge during this period, can often contribute to physical health outputs and persist into adulthood, creating a vulnerability substrate or altering adolescents’ well-being and quality of life [
28,
29]. Independently of body weight, our results show an impairment in HRQoL dimensions, in line with the view in which adolescence is not necessarily the age of highest health, but rather the period of onset of risk factors; this deterioration is more pronounced in girls than boys [
6,
30,
31] (ref).
To try to explain this vulnerability, also in line with previous literature and aforementioned our results, several theories have been formulated [
32,
33]. Probably this different psychosocial picture by sex is explained by the time of pubertal changes in boys and girls, in which girls enter the state of physiological alteration before boys with associated physical and hormonal variations [
34]. This female development is associated with an effect on femininity and thus with psychological outputs such as depressive behaviors, also linked to the time of hormonal maturation.
Within this susceptible framework, it is necessary to highlight that adolescents are more prone to engage in risky behaviour, including an abnormal perception of one’s body weight and thus, an alteration of one’s image. In this field, our previous data collected in a sample of early adolescents demonstrated that weight status correlated more with the psychological dimension in girls, whereas in boys, a stronger association between weight and physical status was observed [
6].
The possible association between body weight control and psychosocial profile creates a vicious circle in which weight stigma may contribute to reinforcing a poor body image, resulting in an increase of stress levels associated with reduced emotion regulation, less rational decision-making, and higher risk behaviors engagement [
35,
36]. It is not a coincidence that during adolescence, everything to do with the body becomes relevant, with important implications on mental health-related aspects, reinforced by the internalization of the aesthetic model imposed by society through social media [
37]. Not surprisingly, the increased stigmatization of overweight/obesity, in the last few years, may be related to more psychological distress and risk behaviors as evidenced by our results, when we analysed health-related quality of life dimensions according to BMI category. In fact, compared to their normal-weight peers, adolescents who are overweight/obese had a reduced perception of psychological well-being, low self-esteem, reduced social relationships with peers and a greater perception of being bullied. In line with our results, these alterations may be amplified in the case of self-perceptions of overweight, considered as predictors of maladaptive coping for stressful events [
38]. In fact, evidence have demonstrated that self-perception of overweight was more powerfully linked with a reduced health-related quality of life and risk beahviors [
38]. Usually, it is well known that overweight or obese adolescents have an impairment in quality of life, characterized by elevated symptoms of depression, emotional difficulties, lower self-esteem, and higher school dropout [
39,
40]. However, little is known about the other side of the coin, i.e., underweight adolescents, although it affects 5% to almost 12% of adolescents, apart from disordered eating, body dissatisfaction, and altered social relationships, as also highlighted in our results [
41]. One of the factors linked to body weight, mainly in the underweight category, is body image, and thus body dissatisfaction, considered one of the most influential factors affecting well-being in adolescents [
42]. Body dissatisfaction is prevalent among adolescents and recent data shows that 24% of normal-weight girls and 22% of normal-weight boys were dissatisfied with their bodies, while in overweight girls and boys, low-level body satisfaction reached 59% and 48% [
43]. The data presented here, which clearly show an impairment of well-being and quality of life, especially in the underweight and obese categories, are, however, perception data and can certainly impair body image. It is not a coincidence that the ‘self-perception’ dimension is lower in the overweight and obese. Although no sex differences in body image-related dimensions were revealed in our data, usually, underweight girls have been shown to have higher body satisfaction as compared to their normal and overweight counterparts [
43]. While previous data demonstrated a sex-effect in this vicious circle, our underweight female population reports a higher perceived economic well-being as compared to boys. There is no clear evidence of this association since few studies have studied the relationship between these dimensions with socio-economic status (SES) or perception of socio-economic status. The few data present are conflicting, showing for example that unhealthy weight control was not limited to upper socioeconomic groups, or in other cases, dietary behavior and attempts to lose weight are more typical of girls of higher SES [
44,
45]. Certainly, social and economic inequalities cause food and body weight inequalities [
46]. In this respect, there is evidence that girls from families of high socio-economic status estimated their weight more correctly than female students of middle and low status, pointing to the ‘mother’s education’ factor as responsible for this association [
47].
Not surprisingly, our results suggest that underweight adolescents, regardless of gender, have a problematic use of social networks. Social media platforms, often accompanied by interactive modes such as likes, comments, and stories, are associated with emotional ups and downs with satisfaction and/or inadequacy, particularly in girls [
48]. Furthermore, data obtained from principal social media platforms show that altered social media use may induce poor body image, self-perception, and eating disorders, as suggested also by our results [
49]. In addition, screen time on social media has been related to an unrealistic view of beauty standards, with subsequent eating disorders and depressive behaviors [
50].
The study has some strengths and limitations. The strength of this study is that little is known about the relationship between HRQoL and body weight categories in Italian late adolescents despite the increase in Italy and other industrialized countries of overweight or obesity probably due to a decrease of the Mediterranean nutritional lifestyle [
51]. A more precise knowledge of this relationship would allow the implementation of targeted and customized preventive strategies based both on the psychosocial profile of the adolescent, also considering a parameter as simple as BMI, considered a potential predictor of health-related quality of life in adolescents, as reported in our previous study [
52].
One of the limitations of the study may be represented by the calculation of BMI because it does not distinguish between lean and fat mass and does not identify the type of obesity. In addition, the use of self-reports for psychological evaluation it could also be a limitation. Moreover, perceptions of well-being and health status may vary from day to day, especially in adolescence when is related to the different emotional backgrounds; thus the results must not be considered in an absolute way, but limited to a specific time window. Finally, the different number of subjects in the different BMI categories, in particular the reduced number of adolescents with obesity, may not show certain significant differences, visible on a larger sample.