Interestingly, leptin (whose plasma levels are elevated in obesity) acts on the ventral striatum to increase the palatability of food [177,178], while PYY (a satiety signal secreted by high intestinal energy and fat content and whose levels are lowered in obesity), decreases orbitofrontal cortex activation to increase food intake [179]. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.