In the current project, the situation applies to individuals with obesity (body mass index (BMI) 35 to 45 kg/m2). In one case the diet is of the type "high-carbohydrate diet" and in the other case "high-fat diet". The idea is that the research subjects should subsist on these diets for the respective 14 days. The energy content of the diet periods must be the same and correspond to the participants' daily needs. Each participant is drawn to one diet for 2 weeks. After a break of at least 3 weeks, the second diet is taken for 2 weeks.

On day 12 of each diet, a venous catheter is placed in one arm for blood sampling and the research person must answer questions about any gastrointestinal complaints in connection with the current diet. At approximately 09:00, the research subject may eat a brunch for approximately 15 minutes (sandwich, juice, fried egg and sausage; 550-600kcal). Venous blood samples are taken before and 15, 30, 45, 60, 90 and 120 minutes after the meal.

The study participant arrives fasted and a venous catheter is placed in one arm for blood sampling. The research subject may eat a brunch for approximately 15 minutes (sandwich, juice, fried egg and sausage; 550-600kcal) and the p-glucose (mM) is checked at 120 min.

The glucemia after the test meal will be compared in high-carbohydrate diet and high-fad diet (paired samples).

The biopsy material is fixed deep-frozen for later analyses.The ketonic activity is represented by the activity the ketogenic enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) in the tissue.

Immunofluorescence of antibodies (giving the geography in the duodenal/jejunal mucosa) and western blotting (semi-assessment compared to a steadily-expressed factor in the mucosa, glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The HMGCS2 will be given as ratio to GAPDH. The western blots in the high-carbohydrate diet will be compared to high-fad diet in each individual (paired samples).

The study participant arrives fasted and a venous catheter is placed in one arm for blood sampling. The research subject may eat a brunch for approximately 15 minutes (Mixed Meal Test (MMT): sandwich, juice, fried egg and sausage; 550-600kcal) and the p-glucose (mM), p-insulin (µUnits/mL) and p-GLP1 (pM) is checked after 15, 30, 45, 60, 90 and120 min.

The aggregated responses to MMT (linear area under the curve minus the baseline value) over 120 min of the respective agent are compared in high-carbohydrate diet and high-fad diet.