INS and Insulin resistance: However, only one study by Laaksonen et al. (2003) has investigated whether CRF in adult life can improve insulin resistance associated with low birth weight [5], and the investigators demonstrated that higher levels of CRF modify the association between low size at birth, as assessed by the ponderal index (kg/m3), with insulin resistance, which was estimated using a validated insulin sensitivity index (QUICKI) in middle-aged men.