Breast milk not only provides ideally balanced nutrients but also contains bioactive molecules (e.g., cytokines, oligosaccharides, IgA and antibodies) that “programme” the infant’s gut microbiome, stimulate the maturation of the intestinal barrier and modulate the immune response, thereby reducing the risk of allergies, obesity and type 2 diabetes [36,37]. Here, CD79A is linked to obesity due to melanocortin 4 receptor deficiency.