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Predictors of the Psychosocial Health of Children and Adolescents With Obesity and Overweight: the Underappreciated Role of Physical Fitness

Background: Childhood and adolescent obesity impacts on various dimensions of psychosocial health, including health-related quality of life (HRQOL) and personal self-concept. Detecting inhibitory and promotive factors of psychosocial health could contribute to the development of more effective obesity management. In this context, the role of physical tness among the predicting variables of psychosocial health has rarely been investigated. Objective: To identify relevant predictors of weight-specic HRQOL and self-concept in the context of childhood and adolescent obesity. Methods: The sample comprised cross-sectional data of 241 children and adolescents with obesity and overweight (12.5 ± 2.1 years; 51.9% girls) and their parents. Information on demographics and active/inactive lifestyle were assessed via parent report. Anthropometric data and physical tness in relation to body weight (W/kg) were measured. Children and adolescents completed standardized questionnaires (GW-LQ-KJ, FSK-K) to assess HRQOL and ve dimensions of self-concept (scholastic, social, physical, behavioral, and self-worth). Results: Backward multivariable linear regression analysis showed that three subdomains of self-concept (physical, behavioral, self-worth) were negatively associated with increasing BMI Z-scores, age, physical activity (hours/week), low parental educational levels, or migration background. HRQOL, however, was only signicantly related to relative physical tness (W/kg; β=8.02, P<0.05) as were scholastic (β=8.92, P<0.05) and social self-concept (social β=8.68, P<0.05). Conclusion: The results add physical tness as a relevant predictor of HRQOL and self-concept of children and adolescents with obesity and overweight. Therapeutic and preventive weight management strategies should therefore consider physical tness as an important additional outcome measure of psychosocial health.


Demographics and Lifestyle Patterns
At the beginning of the program, parents completed standardized questionnaires assessing demographics and lifestyle patterns of both themselves and their children. Demographic and lifestyle variables selected for inclusion in the study were children's sex, age, migration background, time spent in physical activity and on media consumption, and parent's educational background. Parents' educational background was dichotomized into two categories: "high," when both parents had completed secondary school (Abitur/Fachabitur), and "low," when neither parent had an educational degree, a different other than secondary school, or only one parent had completed secondary school [32]. The migration background of the child was treated as a dichotomous variable assessed by the language spoken at home (German/non-German) [33].
Regarding the child's level of physical activity, parents were asked if and for how many minutes per week their child was physically active apart from time spent at school. Media consumption was assessed by asking parents to provide the total number of minutes spent by their child per day watching TV, playing a game console, using the computer/Internet, listening to music, and/or using their mobile phone. For this study, media consumption and physical activity were summed and transformed into continuous variables measured in hours per week.

Physical Fitness
Physical tness was measured in peak mechanical power (PMP [W]) and peak oxygen consumption (VȮ 2max [mL/min], data not shown) using a bicycle ergometer (Ergoline Ergometrics 900) on which the children and adolescents exercised until exhaustion. Prior to testing, participants were familiarized with the test procedure and the bicycle ergometer was adjusted individually (height of seat and handlebar position). Testing began with a workload of 25 W and increased by 25 W every 2 minutes [26]. Throughout the testing session, the participant was verbally encouraged by staff to achieve maximal effort. Due to the comparably larger sample size, peak mechanical power (n = 238) was used as a proxy for physical tness instead of VȮ 2max (n = 228).
Test results were related to body weight as W/kg.

Health-Related Quality of Life
The weight-speci c quality-of-life questionnaire for children and adolescents with overweight and obesity (Fragebogen zur gewichtsbezogenen Lebensqualität für übergewichtige und adipöse Kinder und Jugendliche [GW-LQ-KJ]) by Warschburger and Fromme (2004) [9] is a self-assessment tool speci cally designed to assess the HRQOL of children and adolescents with obesity and overweight. In this study, we used version B of the GW-LQ-KJ which consists of 11 items (eg, "Because of my weight, I was reluctant to go to the public swimming pool"). The children and adolescents were asked to evaluate the statements by estimating the frequency of occurrence in the last 2 weeks on a ve-point Likert scale (ranging from "always" to "never"). The results were recoded so that high values indicated high HRQOL. A summed score was calculated and adjusted to be within a range of 0-100. Dividing the mean individual values by the number of completed questionnaires provided the relative mean. For reliability analysis, Cronbach's α was calculated. The internal consistency of the HRQOL score of the present sample (n = 226) was satisfying, with α = 0.82.

Self-Concept
The FSK-K (Entwicklung eines Fragebogens zur Erfassung von Selbst -und Kompetenzeinschätzungen bei Kindern) is a German version of Harter's Self-Perception Pro le for Children [34] and has been used in previous studies in the context of childhood obesity [35,36]. It is a 30-item self-report to assess the multidimensional self-concept of children. Each item is scored on a scale of 1-4 in an alternative-statement format, with a positive statement on one side (eg, "I want to stay the way I am") and a negative statement on the other side (eg, "I would like to be someone else"). The child decided which side of the description was "sort of true" or "really true" for him/her.
The FSK-K integrates ve scales for assessing perceived domain-speci c self-concept: scholastic competence, social competence, physical appearance, behavioral conduct, and global self-worth. After recoding, the highest domain-speci c competence was de ned as a mean score of 100. Internal consistency of the domains of self-concept was α = 0.79 for scholastic competence (n = 231), α = 0.82 for social competence (n = 223), α = 0.76 for physical appearance (n = 215), α = 0.77 for behavioral conduct (n = 228), and α = 0.71 for global self-worth (n = 215).

Statistical Analysis
Descriptive statistics for anthropometric data, demographics, lifestyle patterns, and physical tness are provided. Continuous variables are shown as means ± standard deviation (SD), minimum (min), and maximum (max), and categorical variables as frequencies and percentages. The in uence of the selected determinants on HRQOL and the dimensions of self-concept were explored by backward stepwise multivariable linear regression analysis, with P > 0.05 designating the removal of variables. Our dependent variables were the HRQOL scale and the scales of each of the ve domains of self-concept. One model was used for each domain. Predictors included in the baseline model were age, sex, BMI Z-score, body fat (%), physical tness (W/kg), physical activity (hours), media consumption (hours), migration background (German [yes/no]), and parental educational background (both with Abitur [yes/no]). A squared term for age was also included as a covariate given that the relationship between HRQOL/ (physical) self-concept and age is nonlinear [5,6]. Signi cance was set at P < 0.05. All analyses were performed using SPSS 27.0.

Results
The average BMI Z-score of the sample was 2.45 ± 0.46, with 212 participants classi ed as obese (88%) and 29 (12%) considered overweight. For a more detailed description of the sample characteristics, see Tables 1  and 2. Low, only one parent/ neither mother nor father have completed secondary school Psychosocial variables are based on scores ranging from 0 (lowest) to 100 (highest) Table 3 presents the six baseline multivariable linear regression models explaining HRQOL and the dimensions of self-concept, ie, scholastic competence, social competence, physical appearance, behavioral conduct, and global self-worth, adjusting for all independent variables. Table 4 summarizes the resulting nal models after using backward stepwise multivariable regression analysis.  BMI Z-score, demographic variables, and lifestyle variables, were not signi cant predictors of HRQOL or social and scholastic competence. We found BMI Z-score and physical activity to be signi cantly associated with only one of the dependent variables investigated. More precisely, BMI Z-score (β=−11.557 ± 2.726, P < 0.001) and self-reported physical activity (β=−0.623 ± 0.301, P = 0.040) signi cantly predicted physical appearance. Jointly with age (β=−0.245 ± 0.641, P = 0.001), the three predictors accounted for approximately 17% of the total variability in the nal physical appearance model (R 2 = 0.171, P < 0.001), which showed no further signi cant associations with the other observed predictors.
Concerning the rst four regression models, predictors of parental educational background and migration background were not signi cant. In the fth model explaining behavioral conduct, however, parents' educational background (β = 7.165 ± 2.942, P = 0.016) and migration background (β = 8.983 ± 4.442, P = 0.045) explained a signi cant proportion of variance (R 2 = 0.057, P = 0.008), indicating that children and adolescents with obesity and overweight who have a migration background or whose parents had comparatively low education assessed their behavioral conduct as worse than their German counterparts.
Higher parental education was also positively associated with global self-worth (β = 8.034 ± 3.005, P = 0.008), and together with age (β=−1.599 ± 0.719, P = 0.028) accounted for approximately 6% of total variability in the nal global self-worth model (R 2 = 0.063, P = 0.005). We were unable to nd further signi cant predictors in the behavioral conduct and global self-worth models. Sex, body fat, age squared and media consumption were not signi cant predictors in any of the nal regression models.

Main Findings
In the context of weight loss and weight management of children and adolescents with obesity, psychosocial aspects such as HRQOL and self-concept play a crucial role [4,10]. Thus, a comprehensive understanding of the dynamics between weight and determinants of psychosocial health and their possible in uencing factors is a key step toward improving obesity prevention and care. In line with the literature, especially perceived physical appearance was inversely related to obesity and physical activity [4]. Additionally, the results demonstrate a negative association between subdomains of self-concept, migration background and low parental education in the context of childhood and adolescent obesity. Lastly, our results revealed that relative physical tness was a major determinant of HRQOL and perceived social and scholastic competence.

Role of Demographic Variables Underlying the Relationship between Weight Status and Psychosocial Health
Consistently with the literature, we identi ed the physical self-concept to be signi cantly associated to BMI Zscores [14,35]. The higher the Z-score, the more dissatis ed participants were with their physical appearance. Many studies have concluded that girls with overweight or obesity are especially susceptible to body dissatisfaction [5,7,37], however, other studies have not yielded results containing differences between the sexes [38, 39]. While we did not nd differences related to sex between any dimension of self-concept or HRQOL, we did nd age to be a signi cant predictor in our study. These results are not surprising when considered in the context of the effects of puberty. Pubescent individuals are particularly vulnerable to low self-esteem and negative body image [5,6,37]. Our ndings support those of earlier research, which suggested that addressing body image should be included in obesity-treatment agendas to improve patients' psychosocial well-being, particularly in adolescence [40].
Migration background and low socioeconomic status have also been identi ed as key determinants of obesity and are also associated with determinants of psychosocial health [12,15,33,41,42]. We found an adverse association between self-concept, migration background and parental educational degree in our sample of children and adolescents with obesity and overweight. This supports the relevance of interventions at an early stage in childhood to address children who -due to their familial background -are particularly at risk of developing obesity and psychosocial impairments [42][43][44]. Considering the observed age effect, the need for early action is especially evident. The strong in uence of familial background and behavior-speci c family variables (e.g. lifestyle patterns and nutrition) in the context of both obesity and the subdomains of self-concept underpin the need for parental involvement in intervention strategies [45,46].
The Association between Physical Fitness, Physical Activity, Media Consumption and Psychosocial Health Our results con rm and reemphasize previous ndings on the positive association between physical tness and HRQOL in childhood [20,22], adolescence [21,24,47,48], and in the context of childhood and adolescent obesity [24]. In the present analysis, we furthermore found relative physical tness to be the strongest and only remaining determinant of two domains of self-concept: perceived scholastic and social competence.
It is important to note that objectively measured tness played a greater role for the selected markers of psychosocial health than subjectively measured physical activity or self-reported media consumption in our sample. In comparison to relative physical tness, self-reported media consumption was not signi cant and physical activity was negatively associated solely to perceived physical appearance. These results were not consistent with previous studies [16,17,49]. The negative relationship between physical activity and appearance may be explained by the fact that engaging in physical activity may reveal fundamental movement-skill di culties compared to nonoverweight peers, leading to an impairment of physical selfconcept [50]. Therefore, our ndings indicate that interventions which -in addition to physical tness improvements -focus on the motor skills of children and adolescents with obesity and overweight may be crucial [50,51].
In weight management programs, most participating families focus on weight loss as the key determinant of program success [48]. Lifestyle changes and psychosocial health outcomes, however, should be regarded as equally important outcome measures -especially when considering the underlying causal relationships [9,10,34]. Our results demonstrate that physical tness is an important factor in this relationship between physical and psychosocial health. Several studies have underlined the importance of physical tness in therapy programs as an essential strategy, not only for weight loss but also for enhancing the emotional, physical, and social domains of HRQOL of children and adolescents with obesity [17,19,23,49]. Because physical tness is associated to both physical and psychosocial dimensions, a focus on improving tness could lead to more sustainable therapy outcomes than short-term weight loss.

Strengths And Limitations
The primary limitation of our study is the cross-sectional design, which does not allow any conclusions to be drawn regarding the causal direction of the relationship between the observed variables. Furthermore, several obesity-relevant factors were not included in our study due to incomplete data such as dietary habits, type of school, single parenting, and parents' BMI. As such, there may be additional factors that could confound the association between the independent variables. Selection bias, information bias and social desirability bias, ie self-reports on physical activity and media consumption, are further limitations. As a treatment-seeking population, the participants potentially shared characteristics, such as motivation, that distinguished them from other groups. Besides, as some data were self-reported, the study is not free from information bias.
Despite these limitations, a major strength of our study is that physical tness, body height, weight, and fat percentage were objectively measured by trained staff according to standardized methods. In addition to the large sample and the number of determinants analyzed, a further strength is the utilization of a weightspeci c HRQOL-measurement tool that has been shown to have good psychometric properties.

Conclusion And Implications
This study identi es physical tness as a key predictor of weight speci c HRQOL and subdomains of selfconcept in the context of childhood and adolescent obesity. The ndings suggest that improvements in physical tness may hold even more promise for positive psychosocial health outcomes in obesity treatment and prevention programs than weight loss or participation in physical activity alone. Future longitudinal studies are required to investigate the robustness and causality of our ndings.
Abbreviations HRQOL Health-related Quality of Life Declarations Ethics approval Ethics approval was granted by the Sports University of Cologne for the ethic request with the number 107/2014 ("Children's Health InterventionaL Trial III -ein ambulantes Schulungsprorgamm zur Pravention und Therapie von Ubergewicht und Adipositas im Kindes-und Jugendalter"). It is provided as supplementary material.

Consent for Publication
All CHILT III participants and their parents were informed that their aggregated data would be anonymized and used for analysis and publication. Consent was provided by the participants' parents.

Availability of Data and Materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests Funding This research did not receive any nancial support from funding agencies in the public, commercial, or notfor-pro t sectors.
Authors' Contributions NE analyzed the data and wrote the manuscript. CJ supervised the analysis, provided methodological guidance, and revised the manuscript. DF, MK, and FH (who work as sports scientists in the program) and LS and SV (who are responsible for the areas of nutrition and psychology in the program) conducted the medical tests and gathered the data. CJ is the leader of the CHILT III program and created the study design. All authors reviewed and approved the nal version of the manuscript.