It is well appreciated that manipulation of the gut microbiome can impact obesity in part via rewiring of the host circadian clock, and reciprocally it has been shown that an intact circadian clock in the host can impact oscillatory behavior of gut microbiota (Org et al., 2015; Seldin et al., 2016; Thaiss et al., 2014; Liang et al., 2015). The gene discussed is CLOCK; the disease is obesity due to melanocortin 4 receptor deficiency.