The db/db mouse is produced by a single gene mutation in the leptin receptor on the C57BL/6J background that results in extreme hyperphagia, subsequent morbid obesity, marked hyperglycemia, a compensatory hyperinsulinemia, and the resultant expansion of pancreatic β‐cell mass37; the data of the present study reiterated the obesity and hyperglycemia present in this strain. The gene discussed is LEPR; the disease is obesity due to melanocortin 4 receptor deficiency.