However, the physiological concentration of FGF23 may not lead to such changes.168 In addition, a study of the elderly Caucasian population showed that serum FGF23 levels were positively correlated with BMI, waist circumference, waist-to-hip ratio, blood lipids, and fat quality.170 Because chronic inflammation is one of the causes of obesity, the relationship between FGF23 and inflammatory factors may be a potential mechanism for obesity and lipid metabolism (Fig. 2a). Here, FGF23 is linked to obesity due to melanocortin 4 receptor deficiency.