INS and Insulin resistance: Concerning this sex difference, 2 previous studies reported relationships between the Ala allele and insulin resistance by sex.21,27 One Italian study found no association between the Pro12Ala genotype and insulin sensitivity in either sex.27 However, a Spanish cross-sectional study reported associations of Ala carriers with lower fasting insulin and higher insulin sensitivity among women only.21 The authors of that study speculated that the different fat distributions of men and women modified the associations.