Dehzad et al. 2023 [28] showed that curcumin intake of 50–1500 mg/day for 4–42 weeks significantly decreased serum leptin levels in health subjects or subjects with metabolic syndrome, NAFLD, impaired glucose tolerance test (IGTT), prediabetes, T2DM, and major depressive disorder in nine publications [29,30,31,32,33,34,35,36,37] (WMD = −4.46 ng/mL; 95% CI −6.70 to −2.21; p < 0.001; I2 = 96.1%, p < 0.001). This evidence concerns the gene LEP and metabolic syndrome.