Scientific evidence for the dietary treatment of type 2 diabetes is insufficient. The investigators hypothesize that a lower carbohydrate content in the diabetic diet than the recommended 55 E% will decrease the postprandial glucose excursion, decrease insulinotropic factors like incretin hormones and decrease their insulinotropic effects due to their glucose dependency. This will reduce postprandial insulin concentration, resulting in an improved insulin sensitivity and glucose metabolism. This clinical study will examine in diabetic, prediabetic and healthy subjects the acute effects of short term highly controlled dietary low carbohydrate intervention on metabolic pathways with respect to insulin action, pancreatic islet function, lipid metabolism, incretin hormones, low grade inflammation in plasma and novel measures of fatty acid metabolism.

Inclusion Criteria:

• Men age 18-70 years
• Postmenopausal women age 55-70 years
• Non-smoker (abstinent at least 6 months)
• HbA1c < 74 mmol/mol
• Fasting blood glucose < 11 mmol/L (mean of 3 measurements)
• Negative (<25 IU/L) plasma glutamate decarboxylase (GAD-65) antibodies (IgG)
• Hemoglobin > 7.5 mmol/L (men); > 6.8 mmol/L (women)
• Normal thrombocytes (140-400 x 109/L)
• eGFR > 45 ml/min per 1.73 m2
• Alkaline phosphatase < 140 IU/L
• Alanine aminotransferase < 70 IU/L
• Normal International Normalized Ratio (0.9-1.2)

Exclusion Criteria:

• Critical illness
• Anti-diabetic drugs other than metformin (maximum of 2000 mg / day)
• Steroid treatment e.g. prednisolone
• Reported or journalized severe food allergy or intolerance
• Reported or journalized gut disease e.g. Crohn's disease, Coeliac disease
• Reported or journalized alcohol dependence syndrome