Resting Energy Expenditure by Gastrointestinal Functional Status

Intestinal failure is a condition in which the gastrointestinal tract is unable to provide adequate digestion and absorption of nutrients, electrolytes, and fluids. Patients may therefore require partial or complete parenteral nutrition. Their resting energy expenditure may be affected by the underlying cause of intestinal failure, changes in body composition, nutritional and metabolic status, and systemic inflammation. Accurate assessment of energy requirements is important for planning individualized nutritional support.

This is a prospective, comparative interventional study with two non-randomized, protocol-defined groups. Group A will include 30 healthy adults with normal gastrointestinal function. Group B will include 62 clinically stable patients with confirmed intestinal failure. Within Group B, approximately 38 participants will have short bowel syndrome and 24 will have other causes of type II or type III intestinal failure, including chronic intestinal dysmotility or extensive disease of the small intestinal mucosa.

The study intervention consists of metabolic, body-composition, and laboratory assessments performed according to a standardized research protocol. Each participant will complete the study during one visit at the Institute of Oncology Ljubljana. The visit will last approximately 90 to 120 minutes. Resting energy expenditure will be measured in the morning, after fasting, in a thermoneutral environment using indirect calorimetry. The indirect calorimetry measurement will last approximately 30 minutes and will determine oxygen consumption and carbon dioxide production.

Body composition will be assessed using dual-energy X-ray absorptiometry to measure lean body mass, fat mass, and bone mineral density. Bioelectrical impedance analysis will also be performed to determine phase angle as an indicator of cellular integrity and function. A blood sample will be collected to assess inflammatory markers, including C-reactive protein and calculated neutrophil-to-lymphocyte, platelet-to-lymphocyte, and lymphocyte-to-monocyte ratios.

Resting energy expenditure will be evaluated as an absolute value in kilocalories per day and in standardized forms, including adjustment for lean body mass, age, and sex. The primary analyses will compare resting energy expenditure between healthy participants and patients with intestinal failure and between patients with short bowel syndrome and patients with other causes of intestinal failure.

Secondary analyses will examine the associations between resting energy expenditure and body-composition parameters, phase angle, and inflammatory markers. The study is intended to improve understanding of metabolic requirements in intestinal failure and to support the development of more individualized nutritional recommendations for these patients.

Inclusion criteria

Group A - Healthy Controls:

• Age 18 to 65 years
• No diagnosed chronic diseases
• No hospitalization within the previous 30 days
• No acute illness within the previous 14 days

Group B - Participants With Intestinal Failure:

• Age 18 to 65 years
• Diagnostically confirmed intestinal failure
• Stable clinical condition

Exclusion criteria

• Uncontrolled hyperthyroidism or hypothyroidism
• Diabetes mellitus with poor glycemic control
• Adrenal gland disease
• Active inflammatory bowel disease, including Crohn's disease or ulcerative colitis
• Celiac disease
• Chronic pancreatitis
• Active gastric or esophageal disease
• Irritable bowel syndrome with significant symptoms
• History of major abdominal surgery that permanently affects gastrointestinal function, except in participants with intestinal failure when this forms part of the condition under study
• Heart failure
• Active ischemic heart disease or recent myocardial infarction
• Chronic obstructive pulmonary disease
• Respiratory failure or need for long-term oxygen therapy
• Progressive neurodegenerative disease
• Dementia impairing the ability to participate
• Severe stroke with significant functional impairment
• Active tuberculosis
• HIV/AIDS with clinically significant immunosuppression
• Active systemic autoimmune disease
• Active malignant disease
• Advanced liver cirrhosis
• Chronic kidney disease
• Treatment with hemodialysis or peritoneal dialysis
• Pregnancy or breastfeeding