Effects of soy protein supplementation on leptin concentration
As outlined in Figure 2 , our preliminary analysis indicated that soy and soy products consumption have no significant difference in serum leptin concentration (WMD = 0.12; 95% CI: -3.26, 3.51; P= 0.921) Also, significant heterogeneity was observed among studies (Cochran’s Q test = 109.59, P= 0.000, I2 = 88.1 %). Subgroup analysis was conducted to check if the effect of soy protein supplementation on serum leptin is different according to gender of participant, baseline BMI, dose of soy protein, duration of studies, supplementation type and study design (Table 3 ). This analysis revealed that the pooled effect of soy protein supplementation on leptin concentration was influenced by dose of soy protein (≤20 g/day versus>20 g/day), in this way that, a significant increase in leptin concentration was found in studies that used more than 20 g/day soy protein (WMD = 4.405; 95% CI: 0.578, 8.232; P= 0.024). Subgroup analysis didn’t show any significant effect of soy protein supplementation on leptin concentration in other subgroups.