Like the db/db mouse model, the hyperphagia and obesity in the Zucker fatty (fa/fa) rat are attributed to hypothalamic defect in leptin receptor signaling, which is also associated with mild hyperglycemia, insulin resistance, mild glucose intolerance, hyperlipidemia, hyperinsulinemia, and moderate hypertension [19]. This evidence concerns the gene LEPR and obesity due to melanocortin 4 receptor deficiency.