Body image is a psychological construct involving body-related thoughts, beliefs, emotions, and behaviours [9]. Negative body image is defined as a person’s negative thoughts and feelings about their body based on their subjective body weight perception [10]. Individuals suffering from poor body image often experience dissatisfaction with their weight and/or body shape [11]. Body weight congruence (BWC) refers to the discrepancy between actual and perceived body size. Inadequate weight perception, especially weight overestimation, is recognised as a critical component of negative body image and is a known factor in the development of eating disorders [12]. Perceiving one’s body weight as “too slim” or “too fat” was associated with poorer mental wellbeing, regardless of weight status [13, 14].

Literature provides a theoretical framework to present the vital role of social media in body image [15]. The Sociocultural Theory has emerged as one of the primary frameworks for conceptualising body image. This theory posits that social agents such as the media, peers, and parents convey strong messages regarding the importance of appearance and pressure to conform to unrealistic body ideals [16–18]. Social media combines aspects of both media and peer influences, as it provides a vehicle for images portraying appearance ideals and an interactive medium allowing for peer feedback through applications such as WhatsApp, TickTok and Instagram [19, 20].

Body image may thus happen directly or indirectly via mediating mechanisms such as internalising body ideals and appearance comparisons. Internalisation means accepting and following body ideals as personal goals [21], whereas appearance comparisons involve evaluating one’s appearance relative to others [22]. Popular adolescent social media platforms, such as Instagram and Snapchat, contain a plethora of idealised body-related content, which tends to endorse muscular ideals (characterised by a v-shaped torso, visible abs, large biceps) and lean/athletic ideals (represented by a toned body with low body fat) for men and boys. For women and girls, social media content is more likely to endorse slim ideals (defined by a lean physique with low body fat and a tight waist), fit/athletic ideals (characterised by a lean and muscular physique), and curvaceous ideals (represented by a thin waist and big bosom/bottom) [23].

Social media platforms may negatively impact adolescent body image by emphasising the significance of looks and unrealistic body ideals [24, 25]. Previous studies have found that adolescents approve and strive for body ideals despite recognising their unrealistic nature [26, 27] and that greater levels of self-objectifying SMU predict body shame among adolescents [28].

Studies linking the use of social media and body image refer mainly to exposure to images and uploading selfies (e.g., [28]). However, today’s youth’s communication on social media includes sharing photos, referring to videos and pictures of their peers or others, commenting on a published story, etc. In other words, exposure to visual content exists within the routine communication of adolescents due to the large amount of documentation they produce and their reference to the documentation of their peers and others. Research showed that social media interaction significantly affects high school students’ self-presentation [29]. Adolescents with large media networks have increasing demands for relationship maintenance, which results in increased photo sharing [30].

Taking and posting selfies on social media is one of the most popular activities associated with adolescents’ SMU, representing a valuable tool to increase their self-presentation via others’ approval. The pictures can be posted through private or group conversations on social media (such as WhatsApp) and/or the private profile or story. Higher exposure to visual content on social media might lead to more social comparisons and appearance concerns reinforcement, possibly creating a vicious cycle; body image-based digital activities may lead to dissatisfied individuals with their appearance to create and manage their best online self-presentation, leading to potentially excessive or problematic SMU, that will maintain their appearance concerns [31].

Although girls usually spend more time on social media (e.g., Instagram and Snapchat) than boys [32], both boys and girls report concerns about appearance pressures and negative evaluations on social media [33]. Gender-dependent differences seem to exist as qualitative research reveals adolescent girls to be less able to control media messages and more often identify social media as the trigger for their body dissatisfaction [34]. In girls aged 11–15, time spent on social media was significantly related to the internalisation of the thin ideal, body surveillance, drive for thinness and more self-objectification [28, 35]. In addition, girls are significantly more involved in and impacted by feedback indices such as “likes” and “comments” [36]. However, much cross-sectional research on social media use and body image focuses on female samples (e.g., [37]) to the exclusion of adolescent boys [38].

Given adolescents’ widespread use of social media and the importance of body image to their development, mental health, and wellbeing, it is necessary to increase the comprehension of the association between SMU categories and body image to mitigate negative impacts. Despite emerging studies linking SMU to body image (e.g., [39–41]), the evidence is still sparse. While previous studies tested the amount of time spent using social media (e.g., [28]) or specific patterns, like problematic SMU (e.g., [42]), we suggest distinguishing between different patterns of uses, following the digital Goldilocks hypothesis [5] to investigate what pater may promote body image. In addition, while other studies link body image with a particular act of posting selfies on social media (e.g., [43]), we aim to examine whether communicating through social media can be associated with the risk of poor body image.

Therefore, our study aimed to investigate the associations between four types of SMU and adolescent body image using data from an extensive, cross-national survey across 42 European and North American countries and regions. We hypothesised that intensive SMU and problematic SMU would be associated with negative body image (negative subjective body weight) and over/underestimated body weight congruence, compared to non-active and active SMU. In addition, we expect these associations to be stronger for girls.

The present study utilised data from the 2018 Health Behaviour in School-Aged Children (HBSC) survey. The HBSC is a World Health Organization (WHO) collaborative cross-national survey of adolescents’ health and health-related behaviours conducted every 4 years. Data were collected from each country following the HBSC internationally approved protocol to ensure consistency in instruments, data collection, and processing procedures [44].

Nationally representative samples of 11-, 13-, and 15-year-old pupils were recruited from classes within schools using a stratified systematic cluster sampling. Data were collected in classroom settings through standardised, self-filled questionnaires on health indicators, social background, and health-related behaviours. The study adhered to the principles of the Declaration of Helsinki, ensuring anonymity and confidentiality of all participants, and participation was voluntary. Ethical clearance was obtained by lead institutions in all HBSC member countries. Out of 47 countries participating in the 2018 HBSC wave, the present study included 42 countries and regions (Figure 1). The eligibility criteria for inclusion were (Supplementary Figure S1): SMU data availability (Bulgaria, Greenland, and Slovakia were excluded), cross-country comparability, and congruence of the collected subjective body weight measure (Macedonia and Serbia were excluded; for further details see Supplementary Figure S1), less than 40% missing values on Subjective Body Weight measure. Exclusively for the SMU-BWC association, having less than 40% missing values on Body Mass Index (BMI) was added as an additional eligibility criterion (Wales, Scotland, Ireland, and England were excluded), resulting in 38 countries/regions in the final analyses.

The overall sample from the 42 countries and regions included 223,454 pupils. Due to missing values on SMU usage categories, 32,562 (14.6%) questionnaires were excluded. Of 190,892 respondents, 51.5% were girls, 62.2% belonged to middle SES, and the distribution by age group was similar (29.0% 11 years old, 34.9% 13 years old, 36.0% 15 years old).

SMU Intensity [45]. Participants identified how often they were in contact via social media with the following four categories of people—close friends, friends from a larger friend group, friends they met through the Internet, and other people (such as siblings or classmates). Five frequency options ranged from “(almost) never to” almost all the time throughout the day and were complemented by “do not know/does not apply” response. Data analysis included participants if at least one response from the four categories of people provided information. The highest frequency reported across the four items was used to create three levels of SMU intensity: a) never or at most weekly, b) daily/several times a day, and c) almost all the time.

Problematic SMU. The Social Media Disorder Scale [8] was used to identify participants displaying signs of possible problematic SMU. The scale showed good validity and reliability across countries [46]. The scale asked participants if they experienced nine items related to addictive behaviours during the past year using binary responses (yes/no): 1) regularly found that you cannot think of anything else but the moment that you will be able to use social media again; 2) regularly felt dissatisfied because you wanted to spend more time on social media; 3) often felt bad when you could not use social media; 4) tried to spend less time on social media, but failed 5) regularly neglected other activities (e.g., hobbies, sport); because you wanted to use social media; 6) regularly had arguments with others because of your social media use; 7) regularly lied to your parents or friends about the amount of time you spend on social media; 8) often used social media to escape from negative feelings; 9) had serious conflict with your parents, brother(s) or sister(s) because of your social media use. Following a validation study, participants who reported six or more symptoms were labelled problematic users, whereas those with five or fewer symptoms were labelled non-problematic users [46].

Four categories of SMU [6]. Four types of social media users were created based on their SMU and intensity scales: 1) non-active user (online contact with others not at all or at the most weekly AND non-problematic user); 2) active user (online contact with others daily but not all time AND non-problematic user); 3) intensive user (online contact almost all the time throughout the day AND non-problematic user); and 4) problematic user (six or more symptoms regardless of the intensity of SMU).

Subjective Body Weight. The self-perception of body image (Ojala and Kenny, 2018) was assessed by asking: Do you think your body is? With five possible responses recorded in three categories, combining extreme answers: below normal weight (much too slim” and “a bit too slim”), normal weight (“about the right size”), and overweight (“a bit too fat”, or “much too fat”). The item showed a high level of agreement in the test-retest analysis [47, 48].

Body Mass Index (BMI). Participants were asked to report on their height and weight. This was used to calculate the body mass index (BMI) for each participant using the formula (weight in kg)/(height in cm²). Participants were further categorised into four body mass categories (thin, normal, overweight, and obese) based on the World Health Organization’s classification criteria [49]. Self-reported height and weight are valid and acceptable proxies of the actual measurement, especially when the latter is not available [50–52].

Body Weight Congruence (BWC). The congruence of Subjective Body Weight and body mass category (BMI) was evaluated by combining these two variables into three categories of BWC: 1) Correct weight perception (Group 0): normal BMI and thinking they are about right weight OR BMI below normal and think they are below normal weight OR overweight and obese BMI and think they are too fat; 2) Overestimation (Group 1): normal BMI and consider themselves too fat OR BMI below normal and consider themselves just right or too fat; and 3) Underestimation (Group 2): BMI above normal and consider themselves too thin or just right OR normal BMI and consider themselves too thin [13, 53].

Sociodemographic variables. Participants were asked to report their gender, and their birth month and year were used to determine their age. Socio-economic status (SES) was assessed using the Family Affluence Scale (FAS) version 3. FAS is a six-item index developed within the HBSC, recognised as a valid indicator of family wealth (Torsheim et al., 2016). Items include a) the number of cars in the family; b) the number of bathrooms in the household; c) the number of computers in the household; d) ownership of a dishwasher; e) having one’s bedroom; and f) the number of holidays spent abroad in the last 12 months prior. The item responses were summed and transformed into a fractional rank score for each country separately [54]. The score, which ranged from 0 to 1, was then categorised as low SES (0–.2), medium SES (0.21–0.8), and high SES (0.81–1) to account for economic differences across the countries [3].

Prevalence estimates of SMU, Subjective Body Weight, and BWC categories were assessed separately by gender for each country (Supplementary Figures S2–S7) and then by age and gender (Supplementary Table S1). Descriptive analyses were performed using the corrected weighted Pearson Chi-square statistic (Table 1). Due to the differences in the prevalence between boys and girls, all regression analyses were stratified by gender.

A set of multinomial logistic regression models was carried out to study the effect of SMU categories within each country on Subjective Body Weight and BWC separately and adjusted by age categories and SES (Supplementary Tables S2–S5). Finally, three-level multinomial regression models introducing the fixed effect played by pupils at the lowest level (level 1) and the two random effects played by schools (level 2) and countries (level 3) were performed through Generalized Structural Equation Modelling (GSEM). The multivariable associations of four categories of SMU with Subjective Body Weight and BWC, considered two separate dependent variables, were stratified by gender and adjusted by age categories and SES. In all the regression analyses, the reference categories were: active users for SMU categories, normal weight for Subjective Body Weight, correct weight perception for BWC, 11 years old for age, and low SES.

All the analyses were performed considering survey design effects (including stratification, clustering, and weighting) using STATA version 17.1 (StataCorp, College Station, TX). Because there were multiple comparisons, a more conservative approach to type 1 error was set, and the significance level of 1% was used.

As shown in Table 1, active social media users (46.2%) were the most prevalent SMU group in our sample, followed by intensive users (31.1%), non-active users (15.5%), and problematic users (7.3%). More than half of respondents perceived themselves as about the right size (56.8%), 16.9% as too thin and 26.4% as too fat. About 2 out of 3 participants presented body weight congruence (62.3%), while 21.4% underestimated and 16.3% overestimated their weight.

Girls and older adolescents were classified more frequently than boys and the younger as intensive or problematic users. The relative proportion of intensive and problematic social media users was higher among those who perceived themselves as too fat than those about the right size. Similarly, higher rates of intensive (32.0%) or problematic (9.0%) SMU participants were observed in the BWC underestimation group compared to the body congruent one (30.4% and 6.3%, respectively). More detailed descriptive information on SMU, Subjective Body Weight, and BWC by country, age category and gender groups can be found in the Supplementary Figures S2–S7 and Supplementary Table S1.

The association between SMU and Subjective Body Weight and BWC are shown in Tables 2, 3 and summarised in Figure 2. Overall, older age, lower socio-economic status and both intensive and problematic social media user profiles seem to play a risk role in the two explored body image outcomes (i.e., Subjective Body Weight and BWC), especially among girls. Concerning subjective body weight, intensive and problematic user girls were up to 80% more likely to perceive themselves as too fat (respectively, OR: 1.14; 95% CI: 1.10–1.18; OR: 1.81; 95% CI: 1.71–1.91) than active users, whereas among boys the positive relationship was significant only for problematic users (OR: 1.34; 95% CI: 1.25–1.44). A weaker positive association was found looking at the self-perception as too thin among intensive (OR: 1.11; 95% CI: 1.06–1.16) and problematic user girls (OR: 1.51; 95% CI: 1.40–1.63) and among problematic user boys (OR: 1.21; 95% CI: 1.12–1.30) compared to active users.

The same significant positive pattern was also observed regarding BWC (Table 3), where both girls and boys with problematic SMU showed a higher likelihood, compared to active users, in terms of overestimation (+52% and +21% in mean, respectively) or underestimation (+34% and +15% in mean, respectively). Furthermore, intensive SMU girls were significantly more likely to present BWC overestimation (+10% in mean) and underestimation (+13% in mean).

The relationship between the non-active social media user profile (compared to the active user) and the two adopted body image measures (Subjective body weight and BWC) deserved a separate presentation of results. Regarding Subjective Body Weight, non-active users, among boys and girls, were about 5%–10% less likely to consider themselves as too fat (respectively, OR: 0.95, 95% CI: 0.90–0.99; OR: 0.91, 95% CI: 0.87–0.96) than active users, while non-active girls (but not boys) were about 20% more likely to think they were too thin (OR: 1.19, 95% CI: 1.12–1.26). Similarly to what was evidenced for Subjective Body Weight, exclusively among girls, non-active SMU was associated with a −12% mean likelihood of weight overestimation (OR: 0.88, 95% CI: 0.83–0.94) and a +19% mean likelihood of underestimation (OR: 1.19, 95% CI: 1.12–1.26).

The present study has important strengths related to the large representative cross-national sample adopting a standard self-administered questionnaire. In addition, the study included a conceptual distinction between four patterns of SMU and two perceptions of body image.

Yet, the study has several limitations. First, the data were obtained using self-report questionnaires. Adolescents do not precisely estimate weight and height, resulting in BMI values that represent merely proxies of the actual measurement. Therefore, further studies are encouraged to use other measurement approaches (e.g., objective data and mixed method approaches) to obtain a more comprehensive picture of the positive and negative impacts of SMU on adolescent body image. Second, the study’s cross-sectional design does not allow for causal inferences. Thus, the present study cannot determine with certainty whether the outcomes observed are an effect of different patterns of SMU. Therefore, further longitudinal studies would be needed to test the direction of the associations. Third, some weight-related measures have a high percentage of missing values (up to 40%). Whether or not substantial differences were found among respondents and non-respondents by socio-economic status, our finding showed slight gender and age differences regarding SMU, subjective body weight and BWC measures. Fourth, a binary indicator of gender (boy vs. girl) did not reflect the experiences of adolescents whose identities do not match this binary conceptualisation. Future research on other underrepresented groups (e.g., minority identities related to gender and sexual orientation) is needed, as they may be characterised by unique experiences of SMU related to body image.

To conclude, the findings in the present study provide a more nuanced understanding of associations between SMU and body image within a large, cross-national adolescent population and highlight the potential risks of intensive and problematic SMU to adolescent self-perceptions. In particular, high exposure to representations of body ideals on social media and increased vulnerability to social feedback and social comparison may harm the development of a healthy body image during adolescence. The findings from this study highlight the need for policymakers, educators, parents, clinicians, and others who care for adolescents to be aware of the associations between SMU patterns and adolescent body image.

On a more practical level, the findings suggest that interventions and preventive programs should be tailored to adolescents’ specific patterns of social media use. More specifically, intensive and problematic use of social media may play the most crucial role in explaining its detrimental consequences for negative body image and over/underestimated body weight congruence. Thus, interventions should enable a shift from maladaptive to harmonious engagement, for example, by supporting adolescents to evaluate contents related to body appearances or beauty standards critically (e.g., idealise thinness, fitness, and esthetical perfection) and adjust their own media consumption (e.g., media literacy) [60] establish and maintain functionality appreciation (a component of body neutrality) by focusing on appreciate the body for the functions it performs (e.g., physical capacities, senses and sensations, creativity, communication with others, and self-care) despite appearance satisfaction [61].