Absolute values of changes (|Δ|) of body mass index (|ΔBMI|, top left panel), fat mass (|ΔFM|) expressed as kg (top right panel), |ΔFM| expressed as % (bottom left panel) and fat-free mass (|ΔFFM|, bottom right panel), before and after a three-week body weight reduction program (BWRP) in obese (OB) children and adolescents with or without metabolic syndrome (METS). Data are expressed as mean ± SD. The values corresponding to each sex-related subgroup (females/males) are reported. All parameters were compared among all subgroups (all, females/males, obese with/without metabolic syndrome) before and/or after the body weight reduction program (BWRP) by using a Wilcoxon signed-rank test (two groups) or a Kruskal–Wallis one-way ANOVA on ranks (more than two groups), when appropriate.