Weight Change and Metabolic Outcomes in Insulin Pump Users with Type 1 Diabetes: Evidence from Randomized Controlled Trials and Observational Studies

Background : Insulin pump therapy improves glycemic control in Type 1 Diabetes Mellitus (T1DM), but concerns about weight gain persist. This review synthesized evidence from randomized controlled trials and observational studies on weight and metabolic outcomes with pump use.

Methodology : A search in PubMed, Scopus, and Web of Science (2015–2026) was performed for studies comparing Continuous Subcutaneous Insulin Infusion (CSII) or automated systems against multiple daily injections in T1DM. The primary outcome was weight change while secondary outcomes included glycemic parameters such as Glycated Hemoglobin (HbA1c) time-in-range and safety. Lastly, risk of bias was assessed with RoB2 and ROBINS‑I.

Results : A toatal of four randomized controlled trials (RCTs) (n = 102–317; follow-up, 13 weeks–2 years) and three observational studies (n = 168–4,643; follow-up, 2–3 years) were included. In RCTs, weight change did not differ significantly between pump and comparator groups. Observational studies showed inconsistent effects on body mass index. Automated closed-loop systems improved glycemic control, with HbA1c reductions of 0.4–0.5% and increases in time in range of 10–12 percentage points, whereas conventional CSII showed no HbA1c advantage over injections when education was equivalent. Insulin requirements were lower with pumps in some studies. Safety profiles were generally acceptable, although infusion set failures and diabetic ketoacidosis occurred more frequently with pumps.

Conclusion : Insulin pump therapy, including automated systems, does not cause clinically significant weight gain over 13 weeks up to 2  years. Automated closed‑loop systems improve glycemic control substantially. Clinicians can recommend automated pumps without concern for weight penalty, but should provide thorough training to mitigate device‑related risks. Conventional CSII without automation adds little benefit over structured injection education.