Key takeaways:

• People with overweight or obesity plus early-stage type 1 diabetes cut their risk for stage 3 disease if BMI dropped to normal range.
• Associations were observed in children and males.

People who test positive for type 1 diabetes autoantibodies and have overweight or obesity may lower their risk for stage 3 type 1 diabetes if they reduce their BMI to normal range, according to data published in Diabetes Care.

“Among individuals with islet autoantibodies who had overweight or obesity, those whose BMI subsequently returned to the healthy range had an approximately 48% lower risk of progressing to clinical, or stage 3, type 1 diabetes,” Maria J. Redondo, MD, PhD, MPH, professor of pediatrics at Texas Children’s Hospital, told Healio. “This association was observed primarily in children and adolescents. Although our observational study cannot establish that BMI normalization prevents type 1 diabetes, the findings suggest that excess weight may be a potentially modifiable contributor to disease progression, particularly in youth.”

Data were derived from Redondo MJ, et al. Diabetes Care. 2026;doi:10.2337/dc26-0833.

Researchers obtained data from 833 children and adults with type 1 diabetes and overweight or obesity who participated in the TrialNet Pathway to Prevention study. Islet autoantibodies for type 1 diabetes were screened at baseline. HbA1c was measured, and oral glucose tolerance tests were performed every 6 to 12 months.

BMI decreased to normal range for 26.8% of the study group during follow-up. Participants with a normal BMI were less likely to progress to stage 3 type 1 diabetes than those who continued to have overweight or obesity (adjusted HR = 0.52; P < .001) Achieving a normal BMI was also tied to lower risk for progression to stage 2 type 1 diabetes compared with having overweight or obesity (aHR = 0.64; P = .003).

In subgroup analyses, lowering BMI to normal levels was linked to reduced risk for stage 3 type 1 diabetes in children (aHR = 0.5; P = .004) and males (aHR = 0.47; P = .005). No association was seen among adults or females. When subgroups were stratified further, reaching a normal BMI was linked to reduced risk for stage 3 type 1 diabetes in boys younger than 12 years (aHR = 0.27; P < .001) but not girls. However, among adolescents aged 12 to 18 years, girls, but not boys, had lower risk for stage 3 type 1 diabetes by reaching a normal BMI (aHR = 0.23; P = .043).

Additional analyses revealed reaching a normal BMI lowered risk for progressing from stage 1 to stage 2 type 1 diabetes (aHR = 0.62; P = .01) and from stage 2 to stage 3 type 1 diabetes (aHR = 0.35; P = .003).

Redondo said the data highlight the importance of monitoring BMI for people who test positive for type 1 diabetes autoantibodies.

“Our findings provide an additional reason to promote healthy nutrition, physical activity and age-appropriate weight trajectories,” Redondo said. “Importantly, BMI normalization in a growing child does not necessarily require weight loss; it may be achieved through weight stabilization while the child continues to grow.”

The study does not identify a specific intervention that may prevent type 1 diabetes, but interventions that help maintain a healthy weight could be used combined with immunotherapies and close monitoring for people with early-stage disease, Redondo said.

For more information:

Maria J. Redondo, MD, PhD, MPH, is professor of pediatrics in the division of diabetes and endocrinology, Children’s Nutrition Research Center and the William T. Shearer Center for Human Immunobiology at Texas Children’s Hospital; and in the department of pediatrics at Baylor College of Medicine. Redondo can be reached at redondo@bcm.edu.