Although a decrease in insulin sensitivity during obesity has been related to a decrease in the number of capillaries present (Baron 1994); de Jongh et al. 2004); Clark 2008), we did not observe significant changes in capillary density in the hindlimb muscle of the mice that were fed a HFD for 6 or 18 weeks (Fig. 5). The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.