Continuous glucose monitoring in the management of patients after gastric bypass

In patients with gastric bypass (GB), high glucose variability (GV) and hypoglycemia have been demonstrated, which could impact the metabolic status and eating behavior. We describe the glucose patterns determined through continuous glucose monitoring (CGM) in two patients with >5 years follow-up after GB and significant weight recovery, who reported hypoglycemic symptoms that interfered with daily activities, and their response to a nutritional and psycho-educative prescription. Case 1: A 40-year-old woman without pre-surgical type 2 diabetes (T2DM) and normal HbA1c, in whom CGM showed high GV and hypoglycemic episodes that did not correlate with the time of hypoglycemic symptoms. Her GV reduced after prescription of a diet with low glycemic index and modification of meal patterns. Case 2: A 48-year-old male with pre-surgical diagnosis of T2DM and current normal HbA1c, reported skipping meals. The CGM showed high GV, 15% of time in hypoglycemia and hyperglycemic spikes. After prescription of a low glycemic index diet, his GV increased and time in hypoglycemia decreased. Through the detailed self-monitoring needed for CGM, we discovered severe anxiety symptoms, consumption of simple carbohydrates and lack of meal structure. He was referred for more intensive psychological counseling. In conclusion, CGM can detect disorders in glucose homeostasis derived both from the mechanisms of bariatric surgery, as well as the patient’s behaviors and mental health, improving decision-making during follow-up. Learning points: High glycemic variability is frequent in patients operated with gastric bypass. Diverse eating patterns, such as prolonged fasting and simple carbohydrate ingestion, and mental health disorders, including anxiety, can promote and be confused with worsened hypoglycemia. CGM requires a detailed record of food ingested that can be accompanied by associated factors (circumstances, eating patterns, emotional symptoms). This allows the detection of particular behaviors and amount of dietary simple carbohydrates to guide recommendations provided within clinical care of these patients. Background Bariatric surgery is the most effective treatment to achieve significant and sustained weight loss in patients with moderate and severe obesity and to attain better control of comorbidities compared with diet and exercise. The gastrointestinal tract is a critical organ for glucose homeostasis, and mixed bariatric procedures such as GB modify different metabolic pathways, as well as hunger and satiety signals (1). Changes in secretion of intestinal peptides, including glucagon-like peptide type 1 (GLP-1) and gastric inhibitory peptide (GIP), are considered among the main mechanisms that promote improvement in glucose and insulin levels (2). Nevertheless, new regulation of glucose metabolism in subjects with GB can also provoke adverse symptoms derived from the altered gastrointestinal function, predisposing to abrupt variability in glucose levels, reportedly higher than those in subjects with type 2 diabetes (T2DM) (3). The term dumping is used to refer to disturbances associated with the adrenergic discharge that occurs with the dilatation of the intestinal loops and to abrupt change in glucose concentrations. Reactive hypoglycemia has been reported in almost two-thirds of these patients, regardless of the diabetes status before surgery (4). These are some of the most common side effects following GB, associated with reduced quality of life and disordered eating behaviors, including responsive carbohydrate consumption and exacerbated insulin secretion. Continuous glucose monitoring (CGM) performed in patients operated with GB has found significant GV, defined as the maximum/minimum index of glucose levels in 24 h, accompanied by significant hyperglycemic spikes, whether in the presence or absence of hypoglycemia (5), and elevation of glucose concentrations above 300 mg/dL after one of these events. Hanaire et al. found values of the mean amplitude of glycemic excursions (MAGEs) among patients operated with GB of 86 ± 58 (mg/dL) and in patients with diabetes of 66 ± 24, respectively (3), compared with values reported for Hispanic population of 21.6 ± 12.6 obtained from a multi-ethnic study (6). Continuous glucose monitoring has also been helpful to confirm the presence of hypoglycemia in patients with and without symptoms of neuroglycopenia after bariatric surgery (5). Two studies have assessed the response of short-term interventions (acarbose and/or reduction in carbohydrate consumption) to reduce hypoglycemic symptoms and GV in patients with GB with favorable results (7, 8). Nevertheless, studies of GV in this population which is rapidly increasing are still limited. This technology is broadly employed in the management of diabetes mellitus, mainly type 1, for its capacity to achieve goals of glycemic control in comparison with multiple measurements of capillary glucose. The capacity to measure detailed glucose patterns has led to the recognition of both GV and hypoglycemia as adverse factors for metabolic and weight control and to impulse their identification and management. These phenomena are not likely to be detected by conventional follow-up, and are imperative to treat, given their potential to influence weight, eating patterns, quality of life and cardiovascular outcomes. We describe patterns of GV (maximum interstitial glucose (IG), time to postprandial peak IG (TP) and MAGE, assessed using Easy GV© software) by CGM in two patients, one female and a male, who we selected for reporting significant hypoglycemic symptoms associated with significant weight recovery (WR) after GB, and the effect of a nutritional and psycho-educative intervention.