LEPR and obesity due to melanocortin 4 receptor deficiency: Additionally, the early spontaneous mutated obesity Zucker obese fa/fa—ob/ob model discovered by the husband-and-wife team of doctors Zucker LM, Zucker TF in 1958 is a rat model of spontaneous genetic mutation of leptin receptor deficiency [22] that allows for the demonstration of excessive visceral and subcutaneous adipose tissue accumulation (Figure 4) [40].