INS and obesity due to melanocortin 4 receptor deficiency: Whether an individual develops obesity-associated co-morbidities may therefore be influenced by genes at many levels: a genetic predisposition to weight gain increases the chance of obesity developing; the ability to develop and maintain healthy fat stores appears to differ between individuals and across ethnic groups; if variants that perturb insulin signalling are present, they may promote the development of insulin resistance; and genes may also influence the ability of β cells to respond with adequate insulin where resistance develops.