Lower glycemic fluctuations early after bariatric surgery partially explained by caloric restriction

We assessed the acute impact of laparoscopic Roux-en-Y gastric bypass (GBP) or sleeve gastrectomy (SG) compared to caloric-matched control group without surgery on glucose excursion in obese patients with type 2 diabetes, and examined if this was mediated by changes in insulin resistance, early insulin response or glucagon-like peptide (GLP)-1 levels.

Six-day subcutaneous continuous glucose monitoring (CGM) recordings were obtained from patients beginning 3 days before GBP (n = 11), SG (n = 10) or fasting in control group (n = 10). GLP-1, insulin and glucose were measured during 75 g oral glucose tolerance testing at the start and end of each CGM.

Post-operative hyperglycaemia occurred after both surgeries in the first 6 h, with a more rapid decline in glycaemia after GBP (p < 0.001). Beyond 24 h post-operatively, continuous overlapping of net glycaemia action reduced from baseline after GBP (median [interquartile range]) 1.6 [1.2-2.4] to 1.0 [0.7-1.3] and after SG 1.4 [0.9-1.8] to 0.7 [0.7-1.0]; p < 0.05), similar to controls (2.2 [1.7-2.5] to 1.3 [0.8-2.8] p < 0.05). Higher log GLP-1 increment post-oral glucose occurred after GBP (mean ± SE, 0.80 ± 0.12 vs. 0.37 ± 0.09, p < 0.05), but not after SG or control intervention. Among subgroup with baseline hyperglycaemia, a reduction in HOMA-IR followed GBP. Reduction in time and level of peak glucose and 2-h glucose occurred after both surgeries but not in controls.

GBP and SG have a similar acute impact on reducing glycaemia to caloric restriction; however, with a superior impact on glucose tolerance.