The main aim of the present study was to analyze changes in HRQoL during and after participation in an outpatient training programme for weight reduction in overweight children and adolescents. Furthermore, changes in HRQoL were related to weight changes.
Results from children’s self-report and parent proxy-report showed significant improvements in several HRQoL dimensions. All subscales reached or outreached population means at follow-up 2. The largest increases were found for weight-specific HRQoL during treatment. By contrast, subscales of generic HRQoL often continued to increase after end of treatment and were mostly not significantly higher than pre-treatment until follow-up 2 with the exception of parent-reported self-esteem. In general, parents reported more marked changes and changes were more obvious with age- and gender-specific norm scores than with raw scores. Correlations in the expected direction, namely associations of weight reduction with HRQoL improvements, were found primarily in girls.
Our results on HRQoL-improvements in participants of a successful weight management intervention are in line with the results of other studies that analyzed mainly obese children and adolescents [7, 10–12, 15, 16, 18, 20]. However, unlike former studies we focused on moderately overweight youth and followed them over multiple measurements until 12 months after end of training. Short-term improvements in our overweight sample turned out to be smaller than those reported in other studies that were conducted among obese youth.
Compared to age- and gender-specific population norms , parent proxy-reports showed significantly impaired HRQoL pre-treatment scores in most subscales. There is no cut-off for clinically relevant HRQoL impairments or changes for the KINDL-R. However, compared to other studies on obese children where scores from 1 SD below the mean of healthy norms were regarded as impaired , baseline scores were only slightly reduced in our participants. Compared to a study that used the KINDL-R in mainly obese participants of an outpatient treatment , we found slightly higher self-report values for the total, emotional and the school score, very similar values for physical well-being, friends, and family, and notably higher values for self-esteem and weight-specific HRQoL. Weight-specific HRQoL was higher than in German overweight and obese youth of the same age-range seeking outpatient treatment in a recent multicenter study .
Concerning changes in HRQoL dimensions, we found the largest increases in weight-specific HRQoL during treatment. Because disease-specific instruments should be more sensitive to changes during treatment , this result was expected. It is in line with previous reports that also found clear improvements of this dimension from pre- to post-treatment in mainly obese youth [11, 12, 15, 16, 20]. Yet the revealed large effects outperform improvements of moderate effect sizes that were reported in most former studies, even if impairments in weight-specific HRQoL in our sample were rather less than in obese samples. However, as our results show, improvements were not constrained to weight-specific HRQoL but also affected on generic HRQoL.
In terms of generic HRQoL we found the most notable increases in self-reported as well as parent-reported self-esteem equivalent to a moderate effect-size, although not all contrasts reached significance. While self-esteem is not included in most HRQoL-instruments and was therefore not covered by all studies, some studies also demonstrated significant increases [12, 16, 20, 40] while others found non-significant but similar absolute increases . Along with the results of reviews on self-esteem in paediatric overweight [7, 41] it can be concluded that weight management programmes positively impact on self-esteem in overweight and obese youth and that these improvements remain relatively stable over time. A striking result not reported by previous research was the high initial self-reported self-esteem in our sample, which further increased over time. It may be that youth with high self-esteem feel more confident to participate in a weight management intervention.
With respect to other HRQoL dimensions the literature reveals inconsistent results which may be due to different instruments, self-report versus parent proxy-report versions and differences between samples and treatments. However, studies with obese participants found significant HRQoL increases on at least some HRQoL subscales during treatment . Griffiths et al.  in their review confirmed an improvement for most HRQoL dimensions except for school functioning (inconsistent results) and family (rarely studied). From our results we can confirm increases during treatment, but in our sample improvements were more pronounced in the long run and looking at parent-reported and norm scores. Effect sizes for univariate time effects on generic HRQoL scores were small to moderate in magnitude.
According to the literature [10, 42, 43], in our study parents reported larger HRQoL impairments than children themselves. Since the decision to seek treatment depends in large part on parents, only those children whose parents perceive greater impairments may be enrolled for weight management programmes. A further explanation for higher self-reported scores is the ‘response shift’ phenomenon, where children with chronic health conditions adapt to their condition, develop coping strategies and re-adjust assessment standards for well-being . It was also supposed that youth may hesitate to acknowledge negative impacts resulting from their weight . Beyond that it seems also possible, that parents aggrandize problems of their children in the knowledge that overweight is detrimental to health and socially prejudiced. It therefore seems important to study both perspectives  and ensure that improvements are also validated with self-reports, which was the case in our study, where self-reported values increased even for dimensions were no significant impairments were evident.
From our results in relation to other studies it can be supposed that the expectable magnitude of positive HRQoL changes during and after weight management training in general varies with the degree of impairment before treatment . Larger increases are to be expected for more impaired HRQoL scores and therefore for proxy-reports, more overweight youth or aspirants for more intensive treatments.
Effects on generic HRQoL were more pronounced when looking at norm scores than on original scores. In general, HRQoL decreases with age during adolescence , so that age effects may partially mask time effects. Thus, whenever possible, examination of standardized values seems preferable and has the further advantage of being more easily interpretable.
The observed changes of HRQoL during our study have important implications for future studies on weight management: As improvements continued after end of treatment on most HRQoL dimensions and most scores were not significantly different post-treatment, longer follow-up periods and larger study populations seem necessary to verify psychosocial improvements at least in only moderately overweight children and adolescents. In addition, it may be that in some preceding studies on obese youth more improvements would have been revealed with longer follow-up measurements. This is in line with Tsiros et al. , who concluded that changes in psychosocial HRQoL dimensions are less common than changes in physical HRQoL because these changes require more time.
Direct correlations between weight reduction and HRQoL changes were low in our study for the overall sample and mainly significant for weight-specific HRQoL. Other studies confirm these low associations. Studies by Yackobovitch-Gavan and colleagues [18, 19], for example, found no significant correlations of weight changes with generic HRQoL during a 12-week intervention. Wille and colleagues  found low and non-significant associations with generic and weight-specific HRQoL, while in the study of Patrick et al.  associations with generic HRQoL changes were no longer significant when adjusted for baseline scores, whereas correlations with changes in weight-specific HRQoL remained significant. The only significant association found by Fullerton et al.  was for changes in physical well-being. Our results concerning associations with improvements in school functioning vary from previous research.
However, unlike other studies we additionally looked at gender-specific associations and found clear gender differences in results, where weight reduction of girls was more favourably correlated with HRQoL changes, while in boys some correlations opposite to the expected direction were found. These gender-specific effects partially averaged out to low correlations for the overall sample. Gender-specific associations were particularly pronounced in terms of long-term changes. None of the previous studies reported associations with long-term changes. Short-term HRQoL changes in our study were often associated with long-term weight changes and pointed to improvements in emotional well-being, self-esteem, school, and weight complaints preceding long-term weight maintenance in girls, while in boys long-term associations were rather unfavourable for generic HRQoL. Possible negative effects as well as gender-specific results should be further monitored, although the gender effects observed in our study may well be sample-specific, for our male subsample was quite small (n = 24). Furthermore, HRQoL scores increased in both boys and girls during and after treatment, so that there is no indication that treatment-induced weight reduction overall showed detrimental effects.
Our results point to HRQoL changes precdicting long-term weight changes in girls rather than vice versa, since on some scales short-term HRQoL changes were associated with long-term weight changes, while no direct correlations were found between long-term changes in HRQoL and long-term weight development. Although no causal effect can be proved by this study, an effect of weight change that occurs later in time on previous HRQoL changes can be ruled out. A possible interpretation, therefore, is that in girls an improved HRQoL, especially in terms of self-esteem and emotional well-being, helped in sustaining a reduced weight, while in boys no such effect was revealed.
In general, weight reduction seems not to be the only critical factor for HRQoL changes during or subsequent to weight management treatment, since it was not consistently associated with HRQoL changes. Further, associations with weight reduction may differ between boys and girls. Because increases in generic HRQoL were not directly related to weight reduction in most cases, improvements may depend primarily on specific content of programme (for example social support or promotion of self-acceptance) more than on diet changes that directly lead to weight reduction, or improvements may not parallel weight changes temporally. This has important implications for practice. While long-term weight reduction may be difficult to achieve for many overweight youth, interventions that lead to HRQoL improvements may increase psychosocial health and well-being even in the absence of weight loss. Hence, they may be an alternative to help those who are not able to achieve a healthy weight in coping with their condition. Future studies should therefore clarify which specific components of the intervention result in HRQoL improvements in girls and boys.
Strengths and limitations
As far as we know, our study is the first to demonstrate HRQoL-changes during and after treatment in moderately overweight children and adolescents. It has the strengths to track changes on generic and weight-specific HRQoL dimensions over multiple occasions until one year after end of treatment from the perspective of the children themselves as well as from parents’ point of view and relate these changes to weight reduction.
However, there are some limitations to be considered, when interpreting our results. At first, reliability of some HRQoL subscales was unsatisfactory, especially for friends, self-esteem and school; although internal consistency was only slightly lower than in other samples [28, 45]. This may have resulted in larger measurement errors and therefore lowered power of statistical tests. Even so, we could demonstrate improvements on these dimensions at least for parent reports, so that this deficiency seems not to have affected our results too much. In future studies, however, more detailed instruments may be preferable in studies on separate HRQoL dimensions. The tendency for social desirable answers in our sample was high. However, we could not find any influence on our results. Because different intervention components were delivered simultaneously, we cannot relate particular components to HRQoL changes. Last but not least, even if the study was designed as RCT, we had no control group to compare our follow-up results to. Given the risk of further weight gain (which is what we observed in untreated controls) we delayed the intervention in the control children for no more than six months. For longer observation periods we had to pool the groups. We therefore cannot draw definite inferences from our analysis about the intervention having caused the observed improvements. Nevertheless, with standardizing HRQoL scores based on age- and gender-specific norms we tried to compensate to some extent for this weakness. Unfortunately, this was not possible in case of weight-specific HRQoL.