Time in range during caloric restriction in type 2 diabetes with obesity

Introduction: To evaluate glycemic changes during caloric restriction with continuous glucose monitoring (CGM)-derived time in range (TIR) in individuals with type 2 diabetes and obesity. Materials and Methods: This 12-week single-arm intervention consisted of 6 weeks of home-delivered meals (800–1,200 kcal/day), followed by 6 weeks of self-managed diet (1,500–1,800 kcal/day for men; 1,200–1,500 kcal/day for women). CGM (14-day sensor) was performed at baseline, weeks 5–6, and weeks 11–12. A 75-g oral glucose tolerance test was conducted at baseline, week 6, and week 12 to calculate the C-peptide index (CPI) and Matsuda index. Results: Participants had a median age of 46.0 years [38.0, 53.5], body mass index (BMI) of 29.2 kg/m² [26.8, 31.2], HbA1c 6.6% [6.0, 7.13], and diabetes duration 2.01 years [0.91, 3.65]. Over 12 weeks, TIR improved from 84.3% to 90.3% (P = 0.041), and BMI decreased from 29.3 to 26.7 kg/m² (P < 0.001). Weight reduction was associated with improved insulin sensitivity, whereas changes in CPI were not significant. CPI showed a stronger association with TIR than the Matsuda index, underscoring the importance of insulin secretion capacity in glycemic control. The association between CPI and TIR was more pronounced participants with higher insulin sensitivity (P = 0.011), suggesting that adequate peripheral sensitivity is required to influence glycemic outcomes. Conclusions: In individuals with type 2 diabetes and obesity, caloric restriction was associated with improved glycemic profiles and reduced body weight. Enhanced insulin sensitivity appears to be the predominant contributor to improved TIR, while preserved β-cell function remains essential for achieving optimal glycemic outcomes.