Overweight and obesity in youth with type 1 diabetes

Objectives Overweight and obesity are highly prevalent in the general population but remain understudied in pediatric type 1 diabetes (T1D). We aimed to estimate the incidence and identify associated factors for developing elevated BMI in a contemporary, real-world cohort of racially diverse lean youth with new-onset T1D. Methods We reviewed medical records from 1,394 youth who were lean (BMI <85th percentile) at the onset of T1D between 2012 and 2024 (excluding those with thyroid or celiac diseases at any time), used BMI trajectory to stratify into mutually exclusive categories (stayed lean, developed overweight, or developed obesity), compared these for baseline characteristics, and estimated relative risk of becoming overweight or obese. Results Over a median of 29.2 months, 64.8 % of youth remained lean, 26.7 % developed overweight, and 8.5 % obesity. We identified significant baseline factors associated with the development of overweight (female, p<0.001; having multiple positive islet autoantibodies, p=0.026; and having lower hemoglobin A 1c , p<0.001) and obesity (female, p=0.003). There were no statistically significant associations with age at T1D diagnosis, health insurance type, or positivity for thyroid or celiac antibodies. Conclusions In sum, over 33 % of lean youth developed elevated BMI within a median of 2.4 years after T1D onset. Early identification of characteristics associated with incident overweight and obesity in youth with T1D may inform targeted weight-management interventions following diagnosis.