As shown (Table 1), the I2 metric was different from 0 (no detectable heterogeneity) for 6 of the 11 genetic variants. Inconsistency of the genetic effects across the three investigations was very large (I2≥75%) for rs9300039 and FTO rs8050136, moderate (I2 between 25–50%) for PPARG rs1801282, CDKAL1 rs10946398 and SLC30A8 rs13266634, and low (I2 up to 25%) for IGF2BP2 rs4402960. In fact the upper 95% CI of I2 extended up to very high levels of inconsistency (73–91%) for all 11 polymorphisms; thus, between-study heterogeneity in the genetic effects cannot be confidently excluded for any of them. Conversely, even when the I2 estimate is high, the 95% confidence intervals typically do not exclude the possibility of homogeneity. I2 is an indicator, not absolute proof of homo- or heterogeneity.
