The male Zucker diabetic fatty (ZDF) rat with fa/fa-genotype is commonly used, as it spontaneously becomes obese and hyperglycemic within the first few months of life due to a leptin receptor defect and a genetically reduced insulin promoter activity.[7–10] Female ZDF rats with fa/fa-genotype similarly become obese and insulin-resistant, but do not progress to hyperglycemia, except when fed a high-fat diet. The gene discussed is INS; the disease is Hyperglycemia.