Supplementary Material for: Variability in Body Mass Index During 2018-2021 for People with Type 1 Diabetes: Real world data from USA, Germany and Australasia.

Introduction: The COVID-19 pandemic necessitated worldwide lockdowns in 2020 and 2021, with restrictions on physical activity and changes in eating habits. Aims: To investigate temporal trends in Body Mass Index (BMI) and BMI Standard Deviation Score (SDS) inSDS) in three international T1D registries between 2018-2021. Methods: Data were extracted from DPV (Germany/Austria/Luxembourg/Switzerland), T1D Exchange Quality Improvement Collaborative (T1DX-QI, US), and Australasian Diabetes Data Network (ADDN, Australia/New Zealand). The period affected by the COVID-19 pandemic was defined as March to December 2020 and March to December 2021 and compared with the respective 9-month periods in 2018 and 2019. Estimated mean BMI (adults ≥ 19 years) and WHO BMI SDS (children and adolescents 54 to < 19 years) were calculated, adjusted for sex, age, HbA1c and diabetes duration. Adjusted mean proportions overweight /obese (BMI ≥ 25 in adults or BMI SDS > 1.282 in children and adolescents 54 to < 19 years) and obese (BMI ≥30kg/m2 or BMI SDS > 2 in children and adolescents 5 to <19 years) were also calculated, adjusted for sex, age, HbA1ce group and diabetes duration. Results: Study population: ADDN (n=14,624, medianan age 15.720.4 years, 510.6% male); DPV (n=62,732, 16.123.1 years, 53.3% male); T1DX-QI (n=229428,970, 17.121.3 years, 52.1% male). In the DPV registry, BMI SDS in children and adolescents and BMI in adults, as well as the mean proportions overweight/obese in children and adolescents increased consistently between 2018 to 2021 (p<0.001). In ADDN and T1DX-QI, variable changes in BMI and BMI-SDS were seen in adults and young people, as well as in mean proportion overweight. Close to 50% of people in all registries were either overweight or obese. Proportions overweight remained relatively stable across the 4 years. The proportion obese increased in children 5-<10 years. Conclusions: A slight increase in BMI and BMI SDS, in DPV observed before the pandemic continued during the pandemic years. Results were more variable in the other registries without a clear pattern although Tthe proportion of overweight and obesity was overall high. Healthy weight remains a priority for people with type 1 diabetes.