Obesity in adults is associated with cognitive impairment and dementia,1, 2, 3 and this is assumed to be a consequence of obesity or obesity related processes such as secretion of bioactive hormonal compounds, altered insulin signalling, diabetes, hypertension, and other cardiovascular disease processes.4, 5, 6, 7, 8, 9 However, some relevant processes begin in earlier life, potentially with different mechanisms. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.