Given the paucity of research on the different BMI categories relating methylation levels in leukocytes in adults of the same population, this study represents the first effort on searching for differences in methylation levels of the ADRB3 gene in varying degrees of obesity, which may help to understand of relations with different categories of the BMI variable. This evidence concerns the gene ADRB3 and obesity due to melanocortin 4 receptor deficiency.