Comprehensive data regarding the incidence of obesity in Type 1 Diabetes (T1D) and its effect on diabetes outcomes is lacking. We sought to address this by analysing a tertiary hospital clinical database.

Method: We extracted clinical and biochemical data for patients with T1D less than 65 years of age who attended a tertiary hospital diabetes clinic between 1998 and 2012 and who had height and weight data recorded.

Results: Of the 501 patients included in the study, 278 (55.5%) were overweight or obese (BMI >25). The mean age and duration of diabetes was similar between those with a BMI >25 (34.6 and 24 years respectively) and those with a BMI <25 (33.0 and 22 years respectively). There was a slight predominance of males in both groups but no significant difference in gender between the groups (BMI <25 55.2% male; BMI >25 57.2% male).

The overweight and obese population used an average of 17 units/day more insulin than the non-overweight population to achieve a similar HbA1c (8.3% versus 8.6%).

T1D patients with a BMI >25 had higher rates of retinopathy (21.6% v’s 12.1%, p-value 0.01), diabetic nephropathy (23.4% v’s 13.5% p-value 0.01) and peripheral neuropathy (7.9% v’s 5.4% p-value 0.23). The differences in the rates of macrovascular complications between the groups were not statistically significant.

Conclusions: In patients with T1D who attend a tertiary hospital outpatient clinic, retinopathy and nephropathy correlate with BMI. This may indicate that aggressive weight management in this group is an important aspect of preventing microvascular diabetes complications.