Introduction and Objective: Adults with type 1 diabetes (T1D) and overweight/obesity (BMI ≥27 kg/m²) have few pharmacologic options for metabolic improvement. We evaluated whether tirzepatide (TZP) in this population was associated with greater weight loss and improved metabolic outcomes versus matched controls. Methods: A retrospective cohort study of adults with T1D from Royal North Shore Hospital/Northern Sydney Endocrine Centre was conducted (2020-2025; searched on Dec 10, 2025). Inclusion criteria were age ≥18 years, BMI ≥27 kg/m², using a continuous glucose monitor (CGM), and follow-up after ≥3 months. TZP group was matched 1:1 to controls. Outcomes included change in weight, BMI, HbA1c, insulin dose, pathology and CGM metrics. Data presented as mean ± SD; Student’s t-test (p0.05). Results: Baseline characteristics were similar between groups (n=18 per group): age 44.0±10.3 vs 42.5±12.7 years, gender 44% female in both groups, BMI 34.4±5.9 vs 34.6±6.0 kg/m², and HbA1c 7.06±1.00 vs 7.36±0.88%. GMI was higher in CON (p0.05). The average duration and dose of TZP was 28.5±11.6 weeks and 5.4±2.69 mg/week respectively. TZP was associated with a reduction in body weight (−9.75±4.76 vs +1.72±4.79 kg; p0.0001) and BMI (−3.38±1.72 vs +0.77±1.99 kg/m²; p0.0001). Total cholesterol was lowered by TZP treatment (-0.24±0.79 vs 0.25±0.46mmol/L, p0.05). HbA1c reduction was greater in the TZP group (−0.58±0.73 vs −0.01±0.61%; p0.05), alongside a significant reduction in total daily dose (TDD) of insulin (−24.7±19.2 vs +9.13±14.3 U/day; p0.05). Time-in-range increased in both groups (+10.6±13.8% vs +2.89±15.1%; p=n.s), and time-below-range remained low in both groups (p=n.s). Conclusion: In adults with T1D and overweight/obesity, TZP use was associated with substantial weight loss and improved cholesterol, HbA1c, and insulin TDD compared with controls, with no increase in hypoglycaemia. Ongoing clinical trials will clarify the generalisability and safety of these findings at scale. Disclosure A.R. Purcell: None. M.S. Longfield: None. S.J. Glastras: Advisory Panel; Current; Abbott Diabetes. Speaker's Bureau; Current; Amgen Inc., AstraZeneca, Boehringer Ingelheim International GmbH, Medtronic. Advisory Panel; Current; Novo Nordisk, Eli Lilly and Company.
Purcell et al. (Fri,) studied this question.