BDNF and obesity due to melanocortin 4 receptor deficiency: While global knockout of the bdnf gene is lethal [13], mice heterozygous for BDNF display chronic hyperphagia and age-dependent obesity [14, 15], and selective deletion of bdnf in the brain causes a phenotype characterized by hyperphagia and obesity, as well as increased abdominal white adipose tissue, changes that are significantly more pronounced in females [16].