Primary objective of the study is to investigate the influence of the disease activity on the resting energy expenditure and the nutritional status in patients with chronic inflammatory bowel disease (IBD). The impact of IBD on the nutritional status and the resting energy expenditure is currently not fully understood. IBD includes two different disease entities, Crohn's disease and ulcerative colitis. Both are characterized by diarrhea, loss of weight, rectal bleeding and abdominal discomfort (abdominal pain, flatulence). In patients with IBD malabsorption, one-sided nutritional behavior, food abandonment, malnutrition, nutrient deficiency and weight loss are common issues. Malnutrition is associated with delayed recovery, impaired wound healing, reduced quality of life and prolonged hospital stay. The malnutrition is not limited to active disease state. Rates for malnutrition in patients with Crohn's disease range from 20 - 85%. Hence, the assessment of the nutritional status is important in the treatment of patients with IBD. Different methods are used to assess the impact of the disease activity on the nutritional status. To investigate the resting energy expenditure the well evaluated indirect calorimetry is used. The principle of the measurement is based on determination of the oxygen absorption during inspiration and the simultaneous determination of the release of carbon dioxide during expiration. The use of bioelectrical impedance analysis (BIA) is a widespread measurement to assess the composition of the body. BIA allows the determination of the fat-free mass, total body water, body cell mass, fat mass and extracellular mass.

Both measurements are non-invasive and reproducible. Additionally different blood parameters are determined such as HDL-subgroups, vitamin b12, folic acid, vitamin K, vitamin D, 25-hydroxy-vitamin D3, zinc, ferritin, albumin, citrulline and routine laboratory (blood count, serum chemistry, coagulation) . Moreover the quality of life is measured through a suitable questionnaire (Gastrointestinal Life Quality Index) as well as the subjective global assessment to estimate the nutritional status.

Furthermore, a secondary aim of the study is to investigate the correlation of HDL-subgroups and the severity of the IBD activity. High-Density-Lipoproteins are a heterogeneous group of lipoproteins with both anti-atherogenic and multiple anti-inflammatory properties. Recent research showed that the quality of HDL-particle is even more important than the quantity. It could be shown that changes in the composition of the HDL could cause an inflammatory status and thus affect the activity of chronic inflammatory disease. Therefore, it is the aim of the study to investigate if changes in the composition of HDL-proteins towards pro-atherogenic HDL-proteins exist.

The study will take place at the University Hospital of Muenster, Germany. Patients who are suitable for participating in the study will be measured and counseled during their regular out-clinic visits. Each patient has to undergo the procedure while they are in an active state of the disease and during remission. It is expected to include 200 patients over 2 years.