Gpr120 deficient mice fed a high fat diet exhibit obesity, glucose intolerance, fatty liver, decreased adipocyte differentiation and lipogenesis (Ichimura et al., 2012), but no difference in body weight between Gpr120 deficient and wild type mice was observed when both groups were fed a normal diet (Ichimura et al., 2012). Here, FFAR4 is linked to obesity due to melanocortin 4 receptor deficiency.