PYY and obesity due to melanocortin 4 receptor deficiency: Animal studies also report that SCFA, namely propionate and butyrate, have an essential role in the prevention of obesity-related insulin resistance at the level of the brain, by activating the Free Fatty Acids Receptors 2 and 3 (FFAR2 and FFAR3) [114,115,116] which suppresses the expression of orexigenic neuron PYY [117] and attenuates ghrelin receptor signaling thus leading to appetite control [118].