Four studies conducted in people with overweight/obesity reported changes in fasting insulin [19,29,31,34] and the pooled analysis showed that a plant-based diet significantly reduced fasting insulin compared with control diets (−4.13 μU/mL, 95% CI (−7.22, −1.04), n = 638, p = 0.009, I2 = 37%) (Figure 3). The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.