These functions, which include bile formation and liver homeostasis, appetite and fat regulation, mucosal renewal processes and resistance to GI toxicity, warrant further detailed investigation with obesity and calorie restriction mouse models and in vitro culture systems that mimic the effects of BChE treatment as well as analysis of human samples from donors with normal and high and low body mass index. This evidence concerns the gene BCHE and obesity due to melanocortin 4 receptor deficiency.