Roux-en-Y gastric bypass (RYGB) accelerates nutrient delivery to the small intestine causing higher peak blood glucose concentration early after meal intake. In the late postprandial period (1 1⁄2-2 h) nadir blood glucose level is lower compared with before operation. In some patients, overt postprandial hypoglycaemia develops, and is typically reported as a complication 1-5 years postoperatively, when maximal weight loss has been obtained. The pathophysiology of postprandial hypoglycaemia involves inappropriate hyper-secretion of insulin associated with exaggerated secretion of the gut hormone glucagon-like peptide-1 (GLP-1) leading to a mismatch between glucose absorption rate, insulin secretion and whole body glucose disposal. We hypothesize that lowering carbohydrate content of meals reduces postprandial glucose excursions whereby GLP-1 and insulin secretion is reduced and reactive hypoglycemia prevented.

Inclusion Criteria:

• RYGB operated patients more than 12 month after operation
• Stable in weight for at least 3 months (+/- 3 kg)
• Plasma glucose below 3.4 mmol/L after screening with test meal (Fresubin drink) or with continuous glucose monitoring

Exclusion Criteria:

• Fasting plasma glucose concentration > 7mmol/L
• Critical illness
• Hgb < 6.5 mM
• Pregnancy or breastfeeding