Background: Obesity and diabetes frequently co-exist, yet their combined impact on complications may differ by diabetes type. This question is increasingly relevant as obesity rates rise among people with type 1 diabetes (T1D), with known high rates of obesity in type 2 diabetes (T2D).
Methods: A retrospective study was conducted of patients with T1D and T2D and known BMI status attending the Royal North Shore Hospital diabetes clinic 2014-2026. Baseline characteristics included risk factors for end-organ complications (e.g., hypertension, dyslipidaemia), and the outcomes examined were cardiovascular disease (defined as coronary artery disease, stroke/TIA, or peripheral arterial disease), diabetic foot disease, metabolic associated fatty liver disease (MAFLD), chronic kidney disease (CKD), and retinopathy. Statistical analyses included t-test, chi-square, and logistic regression (SPSS v25).
Results: Among 1285 T2D and 795 T1D individuals, obesity coexisted in 76.2% and 21.8%, respectively. T2D individuals with obesity were younger (61.65; SD 13.5 vs 64.87; SD 13.4 years; p<0.001), and T1D individuals with obesity were older (41.54; SD 16.2 vs. 37.66; SD 17.6 years; p=0.009) than their non-obese counterparts. Individuals with obesity were more likely to be male in the T1D cohort, but there were no sex differences in the T2D group by obesity. Obesity was associated with higher rates of hypertension in both T2D and T1D (64.7% vs 48.7%; p<0.001, OR 1.93; p<0.001, and 25.4% vs 10.0%; p<0.001, OR 3.08; p<0.001 respectively). Obesity was associated with increased retinopathy (16.2% vs. 9.0%; p=0.007, OR 1.95; p=0.007) in T1D only. No significant association was demonstrated between obesity and MAFLD, CKD or cardiovascular disease in either type of diabetes.
Conclusion: Obesity was associated with increased hypertension in both diabetes types, and increased retinopathy in T1D. Complication screening should therefore be tailored by diabetes type, with obesity management as a priority in both T1D and T2D.