The insulin/IGF‐1 axis of aging is also affected in CR (Weindruch & Sohal, 1997) and IGF‐1 levels are inversely correlated with obesity and aging (Chaker, Aid, Berry, & Holzenberger, 2015; Fontana, Weiss, Villareal, Klein, & Holloszy, 2008; Holzenberger et al., 2003). Here, IGF1 is linked to obesity due to melanocortin 4 receptor deficiency.