Gut Hormones and Nutritional Status After a Standardized Meal.

Stage I

• Participant recruitment

A total of 80 participants (women and men) aged 40-60 years who voluntarily consent to participate in the study will be enrolled:

Control group (G0): 20 participants (10 women, 10 men) with normal body weight - BMI 18.5-24.9 kg/m² Study group I (G1): 20 participants (10 women, 10 men) with overweight - BMI 25.0-29.9 kg/m² Study group II (G2): 20 participants (10 women, 10 men) with class I obesity - BMI 30.0-34.9 kg/m² Study group III (G3): 20 participants (10 women, 10 men) with class II obesity - BMI 35.0-39.9 kg/m²

• Assessment of dietary habits, physical activity, and quality of life

Participants will complete a questionnaire-based survey consisting of the following standardized instruments:

• Questionnaire for the Assessment of Dietary Habits and Opinions on Food and Nutrition (QEB Questionnaire developed by the Committee of Human Nutrition Science, Polish Academy of Sciences);
• International Physical Activity Questionnaire (IPAQ);
• Quality of Life Questionnaire (WHOQOL-BREF);
• The Three-Factor Eating Questionnaire (TFEQ-R18);
• "My Eating Habits: Construction and Psychometric Properties" Questionnaire (N. Ogińska-Bulik, L. Putyński);
• The Hunger-Satiety Scale. The questionnaire survey will enable qualitative assessment of participants' dietary habits, physical activity levels, quality of life, and emotional determinants related to food intake.

Quantitative assessment of dietary intake will be performed using a 24-hour dietary recall collected over three days (two weekdays and one weekend day).

• Nutritional Status Assessment Anthropometric measurements including body height and body weight will be obtained using a calibrated scale with a stadiometer. Waist circumference (cm) will be measured midway between the lower rib margin and the iliac crest, while hip circumference (cm) will be measured at the point of maximum gluteal protuberance. Based on these measurements, the following indices will be calculated: BMI, WHR, WHtR, and RFM.

Body composition analysis will also be performed using dual-energy X-ray absorptiometry (DEXA), which utilizes dual-energy X-ray beams. This technique allows assessment of the whole body and individual body segments by dividing body composition into three main compartments: bone mineral content, lean body mass (excluding bone mineral content), and fat mass.

DEXA is considered a valuable tool for body composition assessment in clinical studies, particularly among individuals with overweight and obesity, as it enables more accurate evaluation of body composition and long-term cardiovascular and oncological risk associated with excess body weight.

The method is safe, rapid, and non-invasive due to the very low radiation dose. Radiation exposure during the examination is approximately 0.001 mSv. The examination is performed in the supine position.

Stage II

• Biochemical analyses: assessment of serum GLP-1, GIP, cholecystokinin, and omentin concentrations in the fasting state and following administration of a standardized meal. Blood samples (10 mL) will be collected for the following laboratory tests: complete blood count (CBC), fasting glucose, fasting insulin, lipid profile (total cholesterol, triglycerides [TG], low-density lipoprotein [LDL], and high-density lipoprotein [HDL]), C-reactive protein (CRP), serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), serum uric acid, serum creatinine. Additionally, fasting blood samples (10 mL) will be collected to determine serum concentrations of GLP-1, GIP, cholecystokinin, and omentin.
• Subsequently, participants will receive a standardized normocarbohydrate meal, and additional blood samples (10 mL each) will be collected at 60, 120, 180, and 240 minutes after meal consumption, individually on the same weekday, in order to assess serum concentrations of GLP-1, GIP, cholecystokinin, and omentin at specified time intervals following standardized meal administration. An isocaloric standardized meal (Nutricia, Poland) will be used in the study, consisting of one and half bottle per participant:

Normocarbohydrate formulation (Nutridrink Standard) Composition of the Standardized Meal - Nutridrink Standard Parameter Per 100 mL Energy 240 kcal Carbohydrates 29.6 g

• of energy 49% Sugars 15.5 g Lactose <0.5 g Fat 9.3 g
• of energy 35% Saturated fatty acids 0.86 g Protein 9.6 g
• of energy 16% Dietary fiber 0 g

Stage III

• Assessment of Resting Metabolic Rate Indirect calorimetry will be performed to accurately measure resting energy expenditure (REE) and determine the energy substrates utilized by the body (carbohydrates and fats).

The examination involves analysis of exhaled air composition (oxygen and carbon dioxide concentrations) using specialized equipment (Q-NRG+, COSMED). Measurements will be conducted using sterile disposable mouthpieces and an oxygen mask. Indirect calorimetry is completely safe, painless, and non-invasive. The examination will be performed once.

The obtained results will be subjected to statistical analysis using Statistica 13.3 software (StatSoft Inc.).

Inclusion criteria

• women and men aged 40-60

Exclusion criteria

• disorders of carbohydrate metabolism,
• endocrine disorders,
• renal and/or hepatic insufficiency,
• gastrointestinal diseases,
• history of gastroenterological or bariatric surgery,
• pharmacological treatment or use of other agents with known or unknown effects on metabolic and hormonal processes,
• other diseases potentially affecting the obtained results,
• pregnancy and lactation.