Impact of Continuous Glucose Monitoring Versus Blood Glucose Monitoring to Support a Carbohydrate-Restricted Nutrition Intervention in People with Type 2 Diabetes.

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• A medically supervised ketogenic diet may result in substantial improvements in glycaemic control, medication reduction, and weight loss in individuals with T2D.

• Both CGM and BGM are effective tools for supporting a ketogenic dietary intervention; however, CGM may offer added benefits of patient confidence and attainment of glycaemic targets.

• The personalisation of glucose monitoring strategies based on a patient’s individual needs, preferences, and resources remains essential in optimizing diabetes care.

Introduction

A randomised, two-arm, parallel-group study was conducted in adults with type 2 diabetes (T2D) to compare changes in time in range (TIR) using continuous glucose monitoring (CGM) versus blood glucose monitoring (BGM) over three months.

Methods

A total of 163 participants with T2D (mean age: 52 years, mean HbA1c: 8.1%) and on glucose-lowering medication were randomly assigned to either the CGM or BGM group for 12 weeks. All participants followed a medically supervised ketogenic diet (MSKD) and were instructed to consume no more than 30 grams of carbohydrates per day. CGM participants used the FreeStyle Libre device, while all participants performed two daily fingerstick tests to measure blood ketone levels in the CGM arm, data from the Libre 2 system was accessible to the study team but not to the participants or the care team, whereas in the BGM arm, both participants and the care team were blinded to the continuous glucose monitoring (CGM) data from the Freestyle Libre Pro system.

The primary outcome was the change in CGM-derived TIR (% time with glucose 70–180 mg/dL; 3.9-10 mmol/L) from baseline to M3.

The secondary outcomes included: (1) change in other CGM-derived metrics from baseline to month 1 (M1) and M3. (2) Percent of participants reaching CGM-derived consensus targets at M3. (3) change in HbA1c from baseline to M3. (4) 90-day average blood-beta-hydroxybutyrate (BHB) levels.

Results

• TIR improved significantly in both groups: by 28% in the CGM group (from 61% to 89%) and by 22% in the BGM group (from 63% to 85%) (p<0.001); no significant difference between arms (p=0.26).

• A greater percentage of CGM users reached the combined glycaemic targets of TIR >70% and time below range (TBR) <4%, by M3 compared to BGM users (p = 0.04).

• Medication use was reduced in both groups between baseline and M3 (p < 0.001), with no differences between CGM and BGM groups (p = 0.79).

• HbA1c decreased by 1.6% (8.1%–6.5%) in the CGM group and 1.5% (8.1%–6.6%) in the BGM group (p < 0.001). A smaller reduction was reported in the BGM group.

• Both groups maintained a lowered-end of nutritional ketosis, with 90-day mean BHB levels of 0.8 mmol/L in the CGM group and 0.7 mmol/L in the BGM group (p = 0.07).

Conclusion:

This randomised controlled trial demonstrated that both CGM and BGM, when combined with a ketogenic diet and remote care, significantly improved glycaemic outcomes (TIR, TAR, and HbA1c). However, there were no statistically significant differences between the two monitoring methods.

• Medically supervised ketogenic diet programs (MSKDP) have been shown to improve glucose control,whether patients use continuous glucose monitoring (CGM) or blood glucose monitoring (BGM).

• Both the CGM and BGM groups saw a reduction in the need for glucose-lowering medication, highlighting the effectiveness of close monitoring during these dietary changes.

• Despite metabolic improvements, both groups showed inadequate fiber intake and poor overall diet quality, emphasizing the need for ongoing nutritional counseling to prevent long-term health issues.

• The study sample was predominantly white, middle-aged, and already enrolled in a digital MSKDP. Future studies should include more diverse populations to enhance generalisability.

• Long-term studies are needed to assess the durability of glycaemic and weight improvements, adherence to carbohydrate-restricted diets, and long-term safety of such interventions.

• Additional research is required to better understand the clinical significance of glucose levels <70 mg/dL, but >54 mg/dL, particularly in individuals at a low risk for hypoglycaemia, including those with prediabetes and people with T2D who are not using insulin. To potentially refine glucose management guidelines and improve patient outcomes in this overlooked range.