Aims
To understand the relationship between insulin resistance (IR), assessed as estimated glucose disposal rate (eGDR), and microvascular/macrovascular complications in people with type 1 diabetes.

Materials and methods
Individuals with a confirmed diagnosis of type 1 diabetes were included in this cross‐sectional study. BMI was categorised into normal weight (18.0–24.9 kg m−2), overweight (25.0–29.9 kg m−2) and obese groups (≥30.0 kg m−2). We categorised eGDR into four groups: eGDR >8, 6–7.9, 4–5.9 and <4 mg kg−1 min−1. Multiple logistic regression was used to identify associations with vascular complications, after adjusting for relevant confounders.

Results
A total of 2151 individuals with type 1 diabetes were studied. Median [interquartile range (IQR)] age was 41.0 [29.0, 55.0] with diabetes duration of 20.0 [11, 31] years. Odds ratio (OR) for retinopathy and nephropathy in obese compared with normal weight individuals was 1.64 (95% CI: 1.24–2.19; p = 0.001) and 1.62 (95% CI: 1.10–2.39; p = 0.015), while the association with cardiovascular disease just failed to reach statistical significance (OR 1.66 [95% CI: 0.97–2.86; p = 0.066]). Comparing individuals with eGDR ≥8 mg kg−1 min−1 and <4 mg kg−1 min−1 showed OR for retinopathy, nephropathy and macrovascular disease of 4.84 (95% CI: 3.36–6.97; p < 0.001), 8.35 (95% CI: 4.86–14.34; p < 0.001) and 13.22 (95% CI: 3.10–56.38; p < 0.001), respectively. Individuals with the highest eGDR category (≥8 mg kg−1 min−1) had the lowest complication rates irrespective of HbA1c levels.

Conclusions
Obesity is prevalent in type 1 diabetes and diabetes complications are not only related to glucose control. IR, assessed as eGDR, is strongly associated with both microvascular and macrovascular complications, regardless of HbA1c levels.