INSIG2 and obesity due to melanocortin 4 receptor deficiency: Other new findings have shed light on a probable genetic origin of obesity; these findings include those reported in studies showing associations between BMI and/or other measures of body composition and SNPs in the catenin, beta like 1 gene (CTNNBL1) [36], the melanocortin-4 receptor (MC4R) [31,32,37-40] and the insulin-induced gene 2 (INSIG2) [36,41-43], among others.