Background: Insulin resistance is well recognized both in type 1 diabetes mellitus (T1DM) and in obesity. Studies concerning the relation between insulin resistance and overweight in T1DM have not yet been carried out.
Methods: Degree of overweight [standard deviation score-body mass index (SDS-BMI)] and daily insulin doses per weight (ID/kg), per body surface (ID/m2), and per ideal body weight (ID/IW) were recorded in 4124 children aged between 5 and 20 yr with a duration of T1DM of 4-5 yr and an adequate metabolic control [hemoglobin A1c (HbA1c) <8.0%]. SDS-BMI was compared between insulin-resistant (ID/kg > or = 1.0) and insulin-sensitive (ID/kg <1.0) children. The ID/kg, ID/m2, and ID/IW were compared between obese (SDS-BMI >1.9) and non-obese children. Multivariate linear regression analysis was conducted for the dependent variables ID/kg, ID/m2, and ID/IW, including age, gender, SDS-BMI, and HbA1c as independent variables.
Results: The 882 insulin-resistant children did not differ significantly (p = 0.447) with respect to SDS-BMI (median +0.38) compared to the 3242 insulin-sensitive children (median SDS-BMI +0.42). The ID/kg was significantly (p = 0.031) lower in the obese children compared to the non-obese children (median 0.80 vs. 0.83), while ID/m2 (median 31.0 vs. 26.2) and ID/IW (median 1.17 vs. 0.85) were significantly (p < 0.001) increased in the obese children. In multivariate linear regression analysis, SDS-BMI was significantly (p < 0.001) associated with an increase in ID/m2 and ID/IW and a decrease in ID/kg.
Conclusions: T1DM children with insulin resistance based on ID/kg are not more overweight than insulin-sensitive children with T1DM. ID/m2 and ID/IW seem to reflect a better tool than ID/kg to describe the influence of overweight on insulin resistance in T1DM.