UCP2 and obesity due to melanocortin 4 receptor deficiency: However, it should be kept in mind that BMI is one phenotype of obesity, other phenotypes included fat body mass index, waist circumference, waist for given BMI, intra-abdominal adipose tissue, hip circumference and etc. Kring SI et al[17] suggested that UCP2 -866G/A was associated with fat body mass index but not BMI.