Rapid Improvement in Diabetes After Gastric Bypass Surgery

Abstract

OBJECTIVEdImprovements in diabetes after Roux-en-Y gastric bypass (RYGB) often occur days after surgery. Surgically induced hormonal changes and the restrictive postoperative diet are proposed mechanisms. We evaluated the contribution of caloric restriction versus surgically induced changes to glucose homeostasis in the immediate postoperative period. RESEARCH DESIGN AND METHODSdPatients with type 2 diabetes planning to un- dergo RYGB participated in a prospective two-period study (each period involved a 10-day inpatient stay, and periods were separated by a minimum of 6 weeks of wash-out) in which patients served as their own controls. The presurgery period consisted of diet alone. The post- surgery period was matched in all aspects (daily matched diet) and included RYGB surgery. Glucose measurements were performed every 4 h throughout the study. A mixed-meal challenge test was performed before and after each period. RESULTSdTen patients completed the study and had thefollowing characteristics: age, 53.2 years (95% CI, 48.0–58.4); BMI, 51.2 kg/m2 (46.1–56.4); diabetes duration, 7.4 years (4.8– 10.0); and HbA1c,8.52% (7.08–9.96). Patients lost 7.3 kg (8.1–6.5) during the presurgery period versus 4.0 kg (6.2–1.7) during the postsurgery period (P =0.01between periods).Daily glycemia in the presurgery period was significantly lower (1,293.58 mg/dLzday [1,096.83– 1,490.33) vs. 1,478.80 mg/dLzday [1,277.47–1,680.13]) compared with the postsurgery period (P =0.02between periods). The improvements in the fasting and maximum poststim- ulation glucose and 6-h glucose area under the curve (primary outcome) were similar during both periods. CONCLUSIONSdGlucose homeostasis improved in response to a reduced caloric diet, with a greater effect observed in the absence of surgery as compared with after RYGB. These findings suggest that reduced calorie ingestion can explain themarked improvement in diabetes control observed after RYGB. Diabetes