Studies from Europe [46] and the United States [47] have indicated that 25%–30% of obese individuals continue to be insulin sensitive; indeed, they maintain metabolic health and do not exhibit the risk factors for cardiovascular disease-hypertension, dyslipidemia, abnormal glucose metabolism-which often accompany obesity [47], and have lower levels of ectopic fat in the liver and skeletal muscle than individuals with insulin resistance [46]. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.