Although the role of MCH and MCHR1 in food intake and energy homeostasis has been of interest for years, it was not until the year 2002 when two seminal papers [20,21] were published supporting the notion of MCHR1 antagonists as potentially useful agents in the treatment of obesity that pharmaceutical and biotechnology corporations joined the competition to develop the first anti-obesity drug. This evidence concerns the gene MCHR1 and obesity due to melanocortin 4 receptor deficiency.