Background: Obesity and its complications have increased in both adults and children, with pediatric populations developing metabolic disorders earlier ages. Long non-coding RNAs, particularly MEG3, are involved in obesity through regulation of lipid metabolism genes including ATF4, FTO, SREBP1, FASN, and ACACA. However, data on MEG3 expression in pediatric obesity are limited. This study evaluated MEG3, FTO, and ATF4 expression in PBMCs from children with obesity and their associations with added sugar intake and lipid metabolism genes. Methods: In this cross-sectional study a total of 71 children aged of 6 to 12 years were included (28 normal weight and 43 with obesity). Anthropometrical and clinical parameters and dietary added sugar consumption were analyzed. Real-time PCR was performed to assess MEG3, FTO, ATF4, SREBP1, FASN and ACACA gene expression in peripheral blood mononuclear cells. Results: The expression of MEG3, ATF4, FTO, SREBP1, FASN, and ACACA was decreased in children with obesity. MEG3 and FTO showed sex-dependent expression in children without obesity, while additional sex-related differences were observed for SREBP1, FASN, ACACA, FTO, and MEG3 in children with obesity. MEG3 was correlated with increased levels of ATF4 and SREBP1, and moderately with FTO and FASN. In insulin resistance (IR) children, MEG3, ATF4, FTO, ACACA, and SREBP1 were reduced, while FASN was increased. Added sugar intake negatively correlated with FTO, SREBP1, and ACACA. Conclusions: The MEG3–FTO–ATF4 axis was altered in children with obesity, showing sex- and IR-related differences. Added sugar intake correlated negatively with lipid metabolism gene expression.