Our current research goal was to investigate the potential role of acylated ghrelin on the development of human obesity by examining: 1) the response of fasting serum acylated ghrelin concentrations in normal weight, overweight, and obese males to short-term overfeeding; 2) fasting serum acylated ghrelin concentrations in each adiposity group before and after overfeeding; and 3) the relationships of fasting serum acylated ghrelin concentrations with fasting glucose and insulin concentrations, blood lipids, and insulin resistance state, before and after overfeeding. This evidence concerns the gene GHRL and obesity due to melanocortin 4 receptor deficiency.