Continuous Glucose Monitoring in Metabolic Surgery

Diabetes is a major global health concern due to its increasing prevalence, associated complications, the burden, and places on individuals, healthcare systems, and societies at large. According to the IDF Diabetes Atlas 2021, about 10.5% of the adults worldwide had diabetes, with T2D accounting for about 90% of these cases. Diabetes poses a significant health challenge in US, with approximately 38.4 million-11.6% of the US adults-diagnosed with the condition. Each year, an estimated 1.2 million adults receive a diabetes diagnosis in the US. Obesity is listed as the most important risk factor associated with diabetes. More than 42% of US are classified as obese and 9.4% have severe obesity. About 30% of patients with T2D have severe obesity. The combination of severe obesity and T2D significantly increases the risk of CVD, non-alcoholic fatty liver disease, and other comorbidities, which contribute to higher mortality rates. To tackle this heavy burden, there's a need for coordinated efforts that encompass prevention, early diagnosis, effective treatment, and patient education. The management of T2D and obesity faces several persistent challenges, including achieving sustainable weight loss and maintaining long-term diabetes remission. While lifestyle interventions and pharmacotherapy often lead to initial improvements, weight regain remains a significant issue, undermining long-term success. Similarly, diabetes remission achieved through these methods is frequently temporary, with many patients experiencing a relapse in glycemic control over time. In this context, metabolic surgery, including procedures such as Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), has emerged as one of the most effective interventions for significant weight loss and long-term diabetes remission, particularly in individuals with severe obesity and T2D. Its metabolic benefits extend beyond weight reduction, directly improving insulin sensitivity and glycemic control. Therefore, integrating metabolic surgery into treatment guidelines and expanding access to eligible patients are critical steps toward addressing the limitations of conventional approaches. While metabolic surgery has been shown to be more effective than intensive medical management for diabetes, its outcomes are often assessed using HbA1c, which has several limitations. HbA1c reflects average blood glucose levels but fails to capture glucose variability or detect hypoglycemia effectively. Additionally, it responds slowly to interventions, making it less suitable for tracking short-term changes post-surgery. These limitations have led to growing interest in CGM as a more precise tool for assessing glucose patterns after metabolic surgery. However, available data on CGM outcomes in this context remain limited, highlighting the need for further research. CGM holds significant potential for improving the assessment and management of obese patients with T2D undergoing metabolic surgery. Unlike traditional measures such as HbA1c, CGM provides real-time, continuous data on glucose levels, offering a detailed picture of glucose variability, postprandial spikes, and hypoglycemic events. This granular insight enables better tracking of short-term metabolic changes immediately after surgery and facilitates early detection of glycemic patterns that may be influenced by the changes in GI tract and dietary patterns after surgery. In the long term, CGM can monitor sustained glycemic control and identify signs of diabetes recurrence, contributing to personalized post-surgical care plans. In addition, post-bariatric hypoglycemia (PBH) is an increasingly recognized complication that can arise following metabolic and bariatric procedures. CGM will enable a better understanding of hypoglycemia unawareness, where patients fail to perceive symptoms despite critically low glucose levels. CGM may have the potential to revolutionize the management of PBH. Despite its promise, research on CGM among patients receiving metabolic surgery remains limited. Several studies have demonstrated the advantages of CGM in identifying post-bariatric hypoglycemia (Table 1). However, limitations of prior studies include their cross-sectional or retrospective design, small sample sizes, a lack of pre-surgery CGM data, and a short GDM monitoring period (most \<10 days) with only one GDM measurement taken after surgery. As a result, there is a growing need for more robust studies, such as RCTs, to validate the effectiveness of this approach and optimize its integration into clinical practice. Therefore, the investigators aim to, Aim 1: To identify the glycemic patterns by using CGM in severely obese patients with T2D receiving bariatric surgeries before and after the procedures. Hypothesis: CGM will reveal distinct glycemic patterns in obese patients with T2D undergoing metabolic surgery, with significant improvements in mean glucose control but not glycemic variability compared to baseline measures. Aim 2: To investigate if the metrics that are derived from CGM data before and after the surgery can predict post bariatric hypoglycemia. Hypothesis: Metrics derived from CGM data, such as time in range, glycemic variability, and mean glucose levels, can reliably predict the likelihood of post bariatric hypoglycemia, with specific thresholds or patterns serving as robust predictors of long-term glycemic control. Aim 3: To investigate the effect of CGM use on the prevention of post bariatric hypoglycemia, as well as the influence of dietary content, formulation, and patterns on glycemic responses. Hypothesis: Dietary content, formulation, and patterns significantly influence glycemic responses in obese patients with T2D, with higher fiber and protein intake, balanced macronutrient formulation, and consistent meal patterns associated with improved glycemic control and reduced risk of post bariatric hypoglycemia as measured by CGM after the surgeries.