Effect of Tirzepatide on Body Weight and Diabetes Control in Adults With Type 1 Diabetes and Overweight or Obesity.

Objective: To determine the effect of tirzepatide on weight, diabetes control, and insulin requirements, and its safety profile in adults with type 1 diabetes (T1D) and overweight or obesity.

Patients and methods: This is a retrospective study of adults with T1D using tirzepatide for overweight/obesity treatment between June 1, 2022, and October 31, 2023, at Mayo Clinic. Fifty-one patients fulfilled inclusion and exclusion criteria (adults with established T1D diagnosis and a body mass index ≥27 kg/m² using tirzepatide for 3 months or longer and without a history of bariatric surgery or active malignancy). Data were collected from the electronic medical record and reported as median (Q1-Q3).

Results: Most individuals were female (30, 58.8%), White (49, 96.1%), and with obesity class III (21, 41.2%). During a median follow-up time of 8.0 (Q1-Q3: 4.0-10.0) months, the total body weight loss was 8.5% (Q1-Q3: 5.3%-13.8%) (P<.01). At 12 months, total body weight loss was 12.2% (Q1-Q3: 7.3%-19.8%) (n=26). By the last follow-up, hemoglobin A_1c decreased by 0.9% (Q1-Q3: 0.3%-1.1%) (P<.0001) and daily insulin requirements by 31.6% (Q1-Q3: -48.0% to -10.9% (P<.01). Basal and bolus insulin doses decreased proportionally, with a more precipitous decline during the first 6 months of tirzepatide therapy. The use of tirzepatide was associated with an improvement of cardiometabolic parameters. There was no increased incidence of hypoglycemia. The most common side effect was nausea (7, 13.7%).

Conclusion: Tirzepatide for the treatment of overweight and obesity in adults with T1D leads to substantial weight loss, improved diabetes control, and decreased insulin requirements, without worsening hypoglycemia. Future studies are needed to ascertain the long-term effect of tirzepatide in this population, ideally focusing on cardiovascular outcomes.