IRS1 and obesity due to melanocortin 4 receptor deficiency: In the 17CafD group, the opposite situation is observed: the obesity phenotype was more favourable in females than in males: they had lower blood leptin and insulin levels, signs of higher insulin sensitivity, both at the whole body level and at the level of expression of genes related to insulin signalling in the liver (Irs2) and muscles (Irs1 and Irs2).