The skeletal muscle and body fat tissue are insulin sensitive,62 and a recent review further suggested an interplay between obesity and insulin disturbance with links to cognitive dysfunction,63 potentially through metabolic hormones and modulation of plasticity.64 There is growing evidence linking obesity and insulin resistance to cognitive impairment and Alzheimer’s disease.65,66 Thus, elevated MFI may be relevant for the development of cognitive and brain-related traits and disorders. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.