However, unlike in humans with adult-onset obesity (MMWR, 2009; Fuhrman et al., 2011) and adult HFD-fed rodents (Smith et al., 2007), the immune response to a TLR3 ligand is not altered in rats made obese due to neonatal overfeeding (Clarke et al., 2012). Here, TLR3 is linked to obesity due to melanocortin 4 receptor deficiency.