The participants had a mean BMI-SDS of 3.1 (0.7 SD) and mean age of 10.4 years (2.8 SD). Approximately 90% of the participants were predisposed to obesity, half of these from both parents. Only one child was due to adoption unaware of any predispositions (Table 1). At baseline boys were more obese (mean BMI-SDS 3.3 (0.7 SD) vs. 2.9 (0.6 SD), p < 0.001) with broader mean waist circumference (93.9 cm (15.4 SD) vs. 87.4 (14.0 SD), p = 0.02), lower mean fat percentage (32.8% (6.1SD) vs. 37.0 (5.3 SD), p < 0.001) and more hungry ((mean VAS 6.7 (2.3 SD) vs. 5.6 (2.4 SD), p = 0.03) than girls. No other differences in baseline characteristics or predispositions were found between the two groups.

Throughout the trial 81 children (68.5%) achieved a BMI-SDS reduction (< -0.1 ∆BMI-SDS), 19 children (15.8%) experienced no change (-0.1–0.1 ∆BMI-SDS) and 20 children (16.7%) increased BMI-SDS (> 0.1 ∆BMI-SDS). There were no demographic or anthropometric differences at baseline between the three BMI-SDS groups (Table 2).

Mean time between the first and last VAS measurement was 26.4 months (13.9 SD). On average 2.7 VAS measurements were completed for each participant.

As outlined in Table 3, a significant decrease in bullying (0.6 median (0.0–4.7) IQR vs. 0.0 median (0.0–0.6) IQR, p < 0.001), and in motivation (10.0 median (9.0–10.0) IQR vs. 9.6 median (7.0–10.0) IQR, p = 0.002), was observed. No significant changes were found for JoL, QoL, appetite, or Bpc.

Stratified by sex, boys experienced decreased mean appetite (6.7 (2.3 SD) vs. 5.7 (2.6 SD), p = 0.04), bullying (0.4 median (0.0–4.8) IQR vs. 0.0 median (0.0–0.8) IQR, p = 0.03), and motivation (10.0 median (8.9–10.0) IQR vs. 8.9 median (6.6–10.0) IQR, p = 0.003). Girls experienced decreased bullying (0.6 median (0.0–4.7) IQR vs. 0.0 median (0.0–0.6) IQR, p < 0.001).

Children who achieved a weight loss (< -0.1 ∆BMI-SDS) experienced reduced bullying (1.0 median (0.0–4.7) IQR vs. 0.0 median (0.0–0.6) IQR, p < 0.001) and motivation (10.0 median (9.0–10.0) IQR vs. 9.6 median (7.3–10.0) IQR, p = 0.027). Children without change in BMI-SDS (-0.1 to 0.1 ∆BMI-SDS) experienced loss of motivation (10.0 median (9.7–10.0) IQR vs. 9.7 median (5.7–10.0) IQR, p = 0.046). No change was observed for those with increased BMI-SDS (data not shown).

Comparing the relative changes in VAS for boys and girls, mean JoL in girls increased significantly ((0.73 (2.08 SD) girls) vs. (-0.04 (2.10 SD) boys), p = 0.048).

Children with reduced BMI-SDS increased their mean QoL (0.65 (2.49 SD)), compared to no change BMI-SDS (-0.36 (1.55 SD)) or increased BMI-SDS (-0.96 (2.27 SD)), p = 0.01 (Table 3). Reducing BMI-SDS also increased mean JoL and mean Bpc, although non-significant (p = 0.14 and p = 0.07, respectively, Table 3), compared with children with increasing BMI-SDS.

For the last visit, regression analyses showed similar results, when investigating the association between the relative change in VAS as a function of the relative change in BMI-SDS over time (years). We here observed a significant inverse association for VAS1 JoL (-1.57 (0.74 SD) CI (-3.02 to -0.10)) VAS2 QoL (-1.71 (0.84 SD) CI (-3.38 to -0.05)) and VAS6 body perception (-2.78 SD 1.29 CI (-5,31 to -0.22)). Non-significant tendencies were observed for bullying (2.02 (1.15 SD) CI (-0.19 to 4.23)) and motivation (-1.94 (1.01 SD) (-3.95 to 0.68)).