A clinical study of adults with a body mass index of at least 30 is undertaken. About 8% of these individuals do not have hyperphagia but are found to have normal levels of leptin and ghrelin, along with a diminished basal metabolic rate. A mutation in which of the following genes is most likely present in these individuals?

There are "obesity" genes that may play a role in metabolic pathways. About 5% to 8% of obese adults have a mutation in the MC4R gene, and even though there are abundant fat stores and plenty of leptin, the lack of MC4R to drive energy consumption leads to weight gain. Leptin is the product of the ob gene, and mutations reduce leptin levels that signal satiety, but such mutations are rare. Mutations in OB-R encoding the leptin receptor are seen in about 3% of cases of early-onset obesity with hyperphagia in children. POMC is in a catabolic pathway stimulated by leptin, but mutations are rare, and affected individuals typically have childhood-onset with hyperphagia. Peroxisome proliferator-activated receptor gamma (PPARg) is stimulated by the thiazolidinedione drugs and leads to a reduction in free fatty acids, reduction in resistin, and decreased insulin resistance.