NPY and obesity due to melanocortin 4 receptor deficiency: Already at the age of 4 months homozygous OE-NPYDβH mice were characterized by 7–8% increase in body weight, 55–74% increase in WAT mass, hypertrophic adipocytes, impaired glucose tolerance and insulin resistance in comparison with WT control mice.20 Along with obesity, they also develop hepatosteatosis.20, 21 However, food intake and energy expenditure are normal in OE-NPYDβH mice and thus the metabolic phenotype is suggested to result from the direct effects of NPY on peripheral tissues and the downregulation of sympathetic tone.20