Weight changes following the initiation of new anti-hyperglycaemic therapies

Objective: The objective of this study was to quantify 1-year weight gain associated with the initiation of sulphonylurea (SU), metformin, insulin and thiazolidinedione (TZD) therapy in a representative real world population of type 2 diabetic patients. Research Design and Methods: The study population was 9546 members of Kaiser Permanente North-west (KPNW) who initiated an anti-hyperglycaemic drug between 1996 and 2002 and continued use of that drug for at least 12 months without adding other therapies. Change in weight was calculated as the annualized difference between baseline and follow-up weight and was adjusted for demographic and clinical characteristics. We then compared the weight changes observed in patients newly initiating SU, metformin, insulin and TZD therapies. Results: After adjustment for demographic and clinical characteristics that might affect weight change, metformin initiators lost an average of 2.4 kg while all other groups gained weight. SU initiators gained the least (1.8 kg), followed by insulin initiators (3.3 kg) and TZD subjects (5.0 kg). All comparisons were highly statistically significant. Conclusions: In an observational study of 1-year weight changes following the initiation of SUs, metformin, insulin or TZDs, we found similar but somewhat smaller weight changes than those previously reported in clinical trials. Our observed weight changes could not be explained by the many other factors we tested and seemed to apply across the full spectrum of diabetes patients. Our report provides valuable information that will allow the patient and clinician to anticipate, and perhaps address, expected weight changes that accompany the initiation of anti-hyperglycaemic drugs.