Weight Change and the Association with Adherence and Persistence to Diabetes Therapy: A Narrative Review

Purpose: Type 2 diabetes (T2D) medication adherence is poor and is impacted by individual drug characteristics. Treatment-associated weight change can affect medication-taking behavior. This review aimed to explore weight change on T2D therapy and consider its impact on adherence and discontinuation. Methods: Searches were conducted in MEDLINE and EMBASE (2005 to September 2020), and among recent congress abstract books for studies providing data on medication adherence or discontinuation and weight change in people with T2D (PwD). Results: Nine studies meeting the inclusion criteria were identified from 9188 bibliographic records. All three studies exploring weight change and discontinuation reported weight loss to be associated with higher persistence. Seven studies of varying design explored weight change and adherence. Four reported absolute weight change (kg) and adherence: one pooled data from different diabetes medications and demonstrated that self-reported adherence was significantly associated with weight loss; however, three studies found that weight change in adherent PwD was in the direction of the known weight profile (loss/gain) of the evaluated drug. Categorical weight loss (>3%) and adherence were reported in two studies: one reported that numerically more adherent versus non-adherent PwD lost >3% weight regardless of the drug's weight profile, the other showed that early weight loss with a glucagon-like peptide-1 agonist was significantly associated with better adherence. One study reported adherence by categorical weight change; as weight loss increased, adherence scores improved, regardless of drug type. Conclusion: Findings suggest that discontinuation rates may be lower in PwD who lose as compared to those who gain weight on T2D treatment. The evidence base on adherence and weight change is more challenging to interpret due to the range of study designs. Given the importance of weight control in T2D, further research exploring the individual's treatment, weight journey, and behaviors over time should be undertaken.