Weight loss is associated with improved daytime time in range in adults with prediabetes and non-insulin-treated type 2 diabetes undergoing dietary intervention

Aims: To characterize changes in continuous glucose monitoring (CGM)-derived time in tight range (TIR) measures in individuals with prediabetes or non-insulin-treated type 2 diabetes undergoing dietary weight loss intervention and to quantify the association between weight loss and TIR improvement. Methods: Data from the Personal Diet Study, a 6-month behavioural weight loss intervention in adults with prediabetes or non-insulin-treated type 2 diabetes [HbA_1c ≤ 8.0% (64 mmol/mol), managed with diet alone or with metformin], was analysed. Participants wore a CGM for a maximum of 2 weeks at baseline and 6 months. Changes in overall, daytime (06:00 h–23:59 h) and overnight (00:00 h–05:59 h) time in 54–140 mg/dL or 3.0–7.8 mmol/L (TIR_54–140), 70–140 mg/dL or 3.9–7.8 mmol/L (TIR_70–140) and >140 mg/dL or >7.8 mmol/L (TAR_>140) were analysed. The association between weight change and TIR change adjusted for demographic and clinical covariates was computed using linear regression. Results: Baseline and 6 months CGM data from 76 participants (63 ± 8 years, 62% female, 64% White, BMI 33 ± 5 kg/m², HbA_1c 5.8 ± 0.6%) were analysed. Overall TIR_54–140 increased (3.3% [0.3, 6.3]%; p = 0.03), with improvement in daytime (3.8% [0.9, 6.8]%; p = 0.01) but not overnight TIR_54–140 (2.0% [−2.2, 6.1]%; p = 0.36). In adjusted analysis, every 5% points of weight loss was associated with a 3.2% points increase in overall TIR_54–140 (p = 0.016), driven by a 3.5% points increase in daytime TIR_54–140 (p = 0.006). Similar associations were found for TAR_>140 but not TIR_70–140. There were no associations between weight loss and change in any overnight TIR measure. Conclusion: Weight loss was associated with improved daytime TIR_54–140 and TAR_>140 in individuals with prediabetes and non-insulin-treated type 2 diabetes undergoing dietary intervention. The daytime time in tight range measures can complement traditional markers like HbA1c, offering a more comprehensive view of glycaemic variations during dietary weight loss programmes for individuals with prediabetes and type 2 diabetes not on insulin.