Body size, form, composition, and a healthy lifestyle associates with health‐related quality of life among Portuguese children

This study aimed to describe the relationship between body size, form, and composition, and children's lifestyle on health‐related quality of life (HRQoL).


| INTRODUCTION
Obesity in childhood is the most challenging public health issue in the twenty-first century (NCD-RisC, 2017). Portugal recorded a substantial increase in the prevalence of child obesity in the last decades (Padez et al., 2004). Although actual findings suggest that childhood obesity rates in Portugal, as well as in other high-income countries, reached a plateau, this is not true for children from all socioeconomic status (SES), and there is still a considerable proportion of 19.6% of boys and 24.4% of girls aged between 6 and 10 years that are affected by overweight and obesity . These numbers are troubling since previous findings indicate that being overweight early in life is a strong predictor of obesity later in life (Simmonds et al., 2016). Overweight and obesity during childhood are also a precursor for a range of adverse physical and psychosocial health consequences throughout the life-course, such as hypertension and metabolic disorders, low self-esteem, and social exclusion (Lobstein et al., 2004;Singh et al., 2008;WHO, 2016).
The analysis of health-related quality of life (HRQoL) is relevant to understand the effects of overweight and obesity in children (Varni et al., 2007). HRQoL has been described as a broad concept that incorporates an individual's subjective evaluation of their position in life and encompasses their physical and psychological health, independence, social relations, beliefs and relationships with the environment (WHO, 1999). In a review of studies, an inverse relationship between HRQoL and weight status in youth (<21 years) was consistently reported, particularly at the physical and social functioning (Tsiros et al., 2009). This pattern may reflect physical difficulties that arise in children with obesity, and the social stigmatization that occurs even in mild obesity. Moreover, higher degrees of overweight as found to be a significant factor of poorer HRQoL in children (Buttitta et al., 2013), and weight loss may improve HRQoL (Tsiros et al., 2009). Portuguese children with overweight and obesity showed reduced HRQoL levels according to their physical and school-related wellbeing. Additionally, parental education was significantly associated with all HRQoL dimensions from early age, particularly among children with normal weight (Costa et al., 2020).
The influence of the lifestyle on children's HRQoL is still unclear, representing an essential line of research. Previous studies suggest that physical activity (Marker et al., 2018), sleep (Sundell and Angelhoff, 2021), and screen time (Belton et al., 2021) are likely to influence children's HRQoL and their obesity levels (Carissimi et al., 2017). Given that lifestyles are established early and may remain constant across childhood and into adulthood (Mikkila et al., 2005;Luque et al., 2018), it is critical to help children and families establish healthy and active lifestyles. Our study is important in the field of human biology in the analysis of lifestyle variation and their effects on HRQoL and child obesity. The aim of the present study is twofold. Firstly, it examines the correlation between the HRQoL of Portuguese girls and boys and their body's size, form, and composition. Secondly, it attempts to identify the HRQoL dimensions most affected by children's obesity status, in due consideration of a selection of relevant lifestyle determinants of both the HRQoL and overweight/obesity, while paying particular attention to potential sex differences. Our findings make important contributions to the field by: (1) pointing areas where individuals may need support, and (2) identifying factors associated with poorer HRQoL, which may help to inform healthcare policies to improve individuals' wellbeing and quality of life.

| Sampling
This current cross-sectional study is part of a larger project entitled "Inequalities in Childhood Obesity: the impact of the socioeconomic crisis in Portugal from 2009 to 2015" conducted during November 2016 to April 2017. Sampling procedures were the same as those followed in a previous project from 2009 to 2010, to assess childhood obesity prevalence and determinants (Jago et al., 2012;Machado-Rodrigues et al., 2018). In brief, the sampling procedure for the 2009-2010 project was based on a stratified random design that accounted for the number of children by age and sex in each district, to provide a nationally representative survey of children aged 3-10 years. In each district, schools were randomly selected; with a total of 17 509 children assessed at that time.
For the 2016-2017 project, schools participating in the previous project from Coimbra, Lisbon, and Porto districts were selected. A total of 13 787 invitations were sent and 8472 preprimary and primary school-aged children (mean age: 7.17 years, SD: 1.91, 50.8% male) were recruited from 118 schools. Participation rates were 58% in Coimbra, 67% in Lisbon and 60% in Porto.
Protocol approval was granted from the Portuguese Ministry of Education and the Portuguese Data Protection Authority (authorization number 745/2017). The study protocol was performed in accordance with the standards set out in the 1964 Declaration of Helsinki and its later amendments. Approval from each of the participating schools was granted by the school principals.
Information letters describing the objective of the study were disseminated to all parents and written informed consent was asked for their participation and of their child. To parents of children aged 7.5 years and older, an additional consent was asked to allow their participation in a school-based survey, corresponding to the self-administration of a standardized questionnaire. Out of the 8472 children assessed, 3957 were 7.5 years or older. The KIDSCREEN-27 was answered by 1619 children, but 286 were excluded for having missing values.

| Anthropometric measures
Child height and weight were measured by study staff (two for each district), trained by an expert anthropometrist (CP). The measurements were taken following the standardized methodology taught to them. Weight was measured in all children with shoes removed and in light clothing using calibrated scales (Seca, United Kingdom) to the nearest 1/10 of a kilogram and standing height was recorded to the nearest 1/10 of a cm using an upright stadiometer (Seca, United Kingdom). The waist and upper arm circumference were taken using the tape measure with the accuracy of 5 mm (Seca, United Kingdom), and skinfold thickness measurements were collected using skinfold calipers (Seca, United Kingdom). Each measurement was taken twice (three times in skinfolds) to obtain two readings within 0.2 cm and the average of the two closest measurements were recorded. The triceps skinfold was obtained at the midpoint of the right upper arm, halfway between the acromion and the olecranon. The subscapular skinfold was measured at a 45 angle just below the inferior angle of the scapula. The suprailiac measurement was obtained approximately 2 cm anterior and medial to the anterior superior iliac spine. BMI was calculated using the equation kg/m 2 . Waist-to-Height Ratio (WHtR) was calculated as the waist circumference divided by the height, with both given in cm. Body fat percentage was estimated using the Slaughter equation for girls and boys (prepubescent) (Slaughter et al., 1988).
Z-scores were calculated for all of the continuous variables. Children were classified into one of four categories: underweight, normal weight, overweight, and obese based on the International Obesity Task Force (IOTF) cut-off points which are based on age-and sex-specific growth charts for children aged 2-18 years (Cole and Lobstein, 2012). For analytical purposes, overweight with obese categories were combined to form a dichotomous variable (vs. normal weight). The WHtR cutoff point of 0.5 was adopted to define abdominal obesity (Browning et al., 2010).

| Wellbeing
The Portuguese version of the KIDSSCREEN-27 was administered to children aged 7.5 years or older, as a measure of wellbeing (Gaspar and Matos, 2008;Ravens-Sieberer et al., 2007). KIDSSCREEN-27 examines five dimensions of health-related quality of life (HRQoL), namely: (i) Physical Wellbeing (5-items) explores the level of the child's physical activity, (ii) Psychological Wellbeing (7-items) includes items on positive emotions, (iii) Parent Relations and Autonomy (7-items) examines relationships with parents, availability of free time, and satisfaction with financial resources, (iv) Social Support and Peers (4-items) examines the nature of the respondent' relationships with other children, and (v) School Environment (4-items) explores the child's perceptions of his/her cognitive capacity, learning and concentration, and their feelings about school. The first item pertains to children's general health status ("excellent," "very good," "good," "fair," and "poor"). The remaining items present a five-point answer option, with responses of "not at all," "slightly," "moderately," "very," and "extremely" (scoring 1-5) available to participants. Negatively formulated questions were all recoded to have scorings from 1 to 5 with higher values indicating a higher wellbeing. The five KIDSCREEN-27 dimensions were shown to have good internal reliability in this study, with Cronbach alphas ranging from 0.751 to 0.835.
With the intention of assessing wellbeing as a multidimensional construct, a total wellbeing score was calculated by adding the five wellbeing dimensions together. Within each dimension, item scores were summed and transformed to T-scores with a mean ≈50 and SD ≈ 10.
Higher scores indicate a more positive wellbeing.

| Behavioral and family variables
Parents reported their children's bedtime and wake time, which were used to calculate total sleep time. Children that sleep 9-12 h per 24 h were within the recommendations of the American Academy of Pediatrics (Paruthi et al., 2016). Children's participation in an extracurricular organized sport was coded as "yes" or "no." Parents also reported the time (hours/day) spent by the child using screen media devices (e.g., television, computer, electronic video games, tablet, smartphone). Total screen time (i.e., all devices considered) was categorized as below recommendation (<2 h/day) or above recommendation (≥2 h/day) since excessive viewing has been linked to several physical and behavioral problems (Domingues-Montanari, 2017). A healthier index ranging from a score of 1-5 was defined according to the number of healthier indicators (normal weight, no abdominal obesity, good sleep duration, engaging in an extracurricular sport, and low screen-time). Only children with complete information in all the parameters were considered in this analysis. A higher score indicates a healthier body composition and lifestyle.
Father and mother's education were categorized in three levels, according to the years of school completed, as follows: lower (less than or equal to 9 years of school completed), medium (from 10 to 12 years), and high (University degree).

| Data analysis
Descriptive statistics and frequencies were calculated for overall wellbeing, and five wellbeing dimensions (physical, psychological, parental, peers, and school), as well as for body measurements. Independent-samples T-test were used to identify differences in the standardized mean values of quality of life and anthropometric measures, according to sex. After stratification by sex, Pearson's correlations were calculated to examine the relationships between the KIDSCREEN scales and the anthropometric measures. Differences in HRQoL between health-related behaviors categories individually were analyzed by oneway analysis of covariance (ANCOVA). Linear regression analyses were conducted to examine the associations between individual health-related behaviors and HRQoL. Finally, a logistic regression was conducted to examine the likelihood of having high HRQoL based on the healthier index. High HRQoL was classify by using the sex-specific mean normative value from European children (aged 8-11 years) (Ravens-Sieberer et al., 2006). The authors present the values for each category of the KIDSCREEN-27, which we used to established the threshold for the total HRQoL score, namely: 52.59 mean value for boys and 52.75 mean value for girls. The analyses were adjusted for parents' education level and were performed using the IBM SPSS Statistics for Windows version 27.0. A p value of <0.05 was set as statistically significant.
T A B L E 1 Health-related quality of life and anthropometric measurements by sex in a sample of Portuguese Children (n = 1333).

| RESULTS
A total of 1333 children completed baseline assessments, half were boys (48.8%), with a mean age of 9.05 ± 0.75 years. Table 1 shows the sample characteristics on HRQoL and anthropometric measurements by sex. Overall, compared to boys, girls show significantly higher values for BMI, upper arm circumference, tricipital, subscapular and suprailiac skinfolds. Boys presented a higher value of physical wellbeing than girls while wellbeing within the school environment was higher in girls than in boys. The relationships between the variables were examined by calculating Pearson's product moment correlation coefficients both for boys and girls (Table 2). Among boys, negative correlations were found between the physical wellbeing and BMI, waist circumference, WHtR, and subscapular and suprailiac skinfolds. Other weak correlations were found between the body measures and other quality of life indicators, except for parent relations and autonomy. Among girls, negative correlations were found between waist circumference and the subscapular skinfold with physical wellbeing. Other negative and weak correlations were also found regarding other quality of life indicators, except for social support and peers and school environment. Figures 1 and 2 show HRQoL differences between categories of health-related behaviors individually, adjusted for parents' education level. Girls with good sleep duration (9-12 h per day) showed a higher HRQoL than those with poor sleep duration [F(1,608) = 5.67, p = .02; ƞ 2 = 0.01]. Regarding sport participation, girls who were engaged in at least one organized sport outside school reported higher HRQoL than their peers with no sport participation [F(1,623) = 18.55, p < .001; ƞ 2 = 0.03]. No statistically significant differences were found among boys. Table 3 shows the results of the healthier index predicting high HRQoL in Portuguese boys and girls. The logistic regression models were statistically significant: for boys, χ 2 (6) = 17.85, p = 0.01; for girls, χ 2 (6) = 19.93, p =0.01. For boys, the model adjusted for parents' education level, indicated that those with a healthier index of 4 or 5 (the scale varied between 1 and 5) were $ 3 to $5 times more likely (respectively) to achieve greater HRQoL than their peers with 1. However, the model explained only 5% (Nagelkerke R 2 ) of the variance in HRQoL. No statistically significant association was found for girls.

| DISCUSSION
This study describes the relationship between body measurements and self-reported HRQoL among Portuguese school-aged children. The results suggest sex differences in the way how obesity and health-related behaviors associate with HRQoL.
T A B L E 2 Bivariate correlations between HRQoL dimensions and anthropometric measurements for boys (n = 650) and girls (n = 683).

Wt
Ht BMI WC WHtR UAC Tri Sub Supra %Fat Boys HRQoL1 À0.08* 0.05 À0.14*** À0.14*** À0.18*** À0.10** À0.14** À0.19*** À0.17*** À0.15*** Girls and boys with higher values of weight, BMI, waist and upper arm circumference, WHtR, skinfolds and body fat percentage showed reduced physical wellbeing. These results are in line with previous studies even if most of them have only accounted for children's weight status (Tsiros et al., 2009;Meixner et al., 2020;Hovsepian et al., 2017;Wallander et al., 2013). The items composing the Physical Wellbeing dimension reflect the child's general health status, how he/she feels and if he/she has been physically active. Possible co-morbidities associated with childhood obesity such as musculoskeletal problems, may lead to lower levels of physical wellbeing. Numerous studies have shown a negative association between the level of physical activity and overweight status in school-age children (Jiménez-Pav on et al., 2010), including in Portugal (Bingham et al., 2013).
Sex differences appeared in other HRQoL dimensions. A significant correlation between parent-related wellbeing and abdominal obesity was evident in girls only. The present study suggests that girls with abdominal obesity feel more dependent on their parents than those with lower levels of waist circumference and WHtR. Central obesity and obesity were associated with lower HRQoL in a sample of German boys, but not in girls (Meixner et al., 2020;Kesztüs et al., 2013). Some studies have described the families of children with obesity as overprotective which can lead to a child's limited autonomy (Radoszewska, 2017). The question why this pertains only to girls but not to boys (or inversely in other studies) remains unclear and awaits further exploration.
We also found that all body measurements, except for height, were correlated with lower scores for the School Environment dimension (e.g., assessing if the child has been happy at school, got on well at school, been able to pay attention, and got along well with the teachers) in boys only. A review of nine studies performed in the United States, Western Europe, South American, and Asia suggested a consistent and significant association between childhood obesity and poor school performance (Taras and Potts-Datema, 2005). Previous findings suggest that the influence of obesity on academic performance is negative because the child also struggles with social and emotional adjustment that makes peer interaction difficult in the classroom (Shah and Maiya, 2017;Arora et al., 2013). In comparison to normal weight children, children with obesity are teased at least three times more often (Neumark-Sztainer, 2002) and they are often perceived as lazy or stupid (Puhl and Brownell, 2003), which may affect the self-concept of obese children. Further investigation is needed to explore the sex differences but a possible explanation may be related with bullying prevalence rates being higher among boys than girls (Currie et al., 2008).
As measures or indicators of obesity, we observed that the WHtR, as well as the suprailiac and the subscapular skinfolds had the major correlations to HRQoL in both sexes (for boys, also body fat percentage; for girls, also waist circumference). An association between higher WHtR and poorer HRQoL among the adult population was previously reported (Tozetto et al., 2021). An increase in abdominal fat may be associated with decreased gene expression related to increased muscle mass maintenance which contributes to physical damage over time (Bonfante et al., 2017). Abdominal obesity has emerged as a stronger risk factor than general obesity for multiple negative health outcomes not only in adults but also in children (Manios et al., 2008). Furthermore, findings in adults suggest that fat is not always more stigmatized but that shape is sufficiently important in driving fat stigma, with women carrying abdominal obesity being more strongly stigmatized than those carrying gluteofemoral fat (Krems and Neuberg, 2022). To our knowledge, no data is available for children, however, it may be that children with abdominal obesity experience more negative effects of fat stigma than same-weight children without abdominal obesity, which could impact their HRQoL.
We found that health-related behaviors, such as, good sleep duration and practicing an organized sport was associated with higher HRQoL in girls, but not in boys. This result supports prior research confirming the positive influence of sleep duration on HRQoL (Wong et al., 2021;Sundell and Angelhoff, 2021). Less sleep may lead to daytime sleepiness which consequently can reduce alertness and compromise daytime functioning because of fatigue, mood changes and memory difficulties and compromise children's quality of life (Bruce et al., 2017). Previous research in children reported a positive association between physical activity or sport participation and HRQoL (Moeijes et al., 2019;Marker et al., 2018). Many authors have already addressed physical activity as an important determinant of physical and psychological health, suggesting a dose-response relationship in which more physical activity results in greater health benefits (Biddle and Asare, 2011;Janssen and Leblanc, 2010). However, few studies have paid specific attention to a child's sports participation and its positive association with HRQoL (Tsiros et al., 2017;Moeijes et al., 2019). Sports participation may contribute to positive self-perception as well as enhance energy, vigor, pleasant mood, joy, and social skills, especially among girls (Liu et al., 2015;Reed et al., 2009;Peguero, 2008).
Additionally, we found that the children with the higher number of healthier indicators were more likely to have higher HRQoL. Boys with a healthier index of 4 or 5 compared with those with an index of 0 showed greater mean score values of overall HRQoL. Similar results were previously reported for adolescents in Portugal (Marques et al., 2019) and Spain (Solera-Sanchez et al., 2021). Present results are in line with the mentioned studies, by confirming that adhering to several health-related behaviors and (and health indicators) is associated with higher levels of overall HRQoL. However, to our knowledge, no other study has analyzed the combined influence of several health indicators on children's HRQoL.
Given that the school is a meaningful and effective setting to stimulate and support all children in being more physically active (Carson et al., 2014), the implementation of school physical activity programs may have a positive impact on multiple aspects of children's quality of life. Moreover, it is important that future public health strategies focus on multibehavioral health policies, since our combined index showed a positive relationship with higher HRQoL.

| Strengths and limitations
This study assessed a large sample of children from different socioeconomic status, using a well-established standardized questionnaire and a variety of anthropometric measures objectively collected. Children answered the questionnaire in the classroom, not influenced by their parents' answers. Moreover, we adjusted the analyses by father's and mother's education as a proxy measure of SES, which has been considered an adequate indicator of social class when assessing samples of children (Galobardes et al., 2007). However, there are restrictions in an observational study compared with a clinical study, such as missing data and selection bias, which may lead to a lower precision of the study (Morshed et al., 2009) or may reduce the representativity of the studied population. The cross-sectional nature of the design which is useful in identifying associations but cannot determine directionality. It is plausible that poor HRQoL may increase the risk of weight gain through its association with unhealthy lifestyle (Sahle et al., 2020). It is also important to mention that there are other factors influencing children's HRQoL independent of children's sex that have not been considered in our analyses, such as use of health care and the number of disorders and health complaints (Houben-van Herten et al., 2015).

| CONCLUSIONS
Information on children who may be at risk for functional limitations and life dissatisfaction, may direct future sub-groups interventions for improving quality of life. This study shows an association between child anthropometric measures and quality of life, specifically within the dimensions related to physical functioning, school environment and parental relation and autonomy. The results also show that sleep duration and sport participation have a positive relationship with girls' HRQoL, while the combined effect of several healthier indicators has a strong influence on boys' HRQoL. Although our data do not address causality, it is possible that programs combining multiple health-related behaviors may help improve HRQoL for some children.

AUTHOR CONTRIBUTIONS
Daniela Rodrigues was responsible for the study conception and design, and data analysis. Data collection was supervised by Aristides M. Machado-Rodrigues, Augusta Gama, Helena Nogueira, Maria-Raquel G. Silva and Cristina Padez. Cristina Padez was also the project leader and responsible for the funding acquisition. The first draft of the manuscript was written by Daniela Rodrigues and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

ACKNOWLEDGMENTS
We express our sincere gratitude to the participants, parents, teachers and principal from each of the Portuguese primary schools who took part.

CONFLICT OF INTEREST STATEMENT
The authors declare no competing interests. The funder had no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.
CONSENT TO PARTICIPATE Written informed consent was obtained from all individual participants included in the study.