MTHFR and obesity due to melanocortin 4 receptor deficiency: The pooled results indicated that the MTHFR C677T polymorphism was not significantly associated with the risk of being overweight/obesity in all genetic models (recessive model: OR = 1.05, 95% CI = 0.94–1.16, p = 0.411; dominant model: OR = 1.06, 95% CI = 1.00–1.13, p = 0.092; homozygous codominant model: OR = 1.06, 95% CI = 0.94–1.18, p = 0.341; heterozygous codominant model: OR = 1.06, 95% CI = 0.99–1.13, p = 0.588; allelic model: OR = 1.05, 95% CI = 1.00–1.10, p = 0.077) (Table 4, Figures S1–S5).