INS and Insulin resistance: HOMA-IR – Fasting insulin and glucose levels were measured for the twin cohort using the same methods as previously described.12 The homeostasis model assessment-estimated insulin resistance (HOMA-IR) was calculated multiplying overnight fasting plasma insulin (FPI) by overnight fasting plasma glucose (FPG), then dividing by the constant 22.5, i.e. HOMA-IR = (FPI×FPG)/22.515.