Furthermore, serum biomarkers reflective of mitochondrial function, namely FGF21 and mitochondrial open reading frame of 12S rRNA-c (MOTS-c), were analysed in a cohort of adolescents with severe obesity ± MASLD, in which the prevalence of maternal obesity was high (Table 1). Here, FGF21 is linked to obesity due to melanocortin 4 receptor deficiency.