The goal of this clinical trial is to learn if a structured high-protein diet with meal replacements can help with weight loss in adults with overweight or obesity. The main questions it aims to answer are:

Does this diet help participants lose more body weight? Does this diet improve body composition and blood markers such as glucose and cholesterol?

Researchers will compare a structured diet program with meal replacements to a standard low-calorie diet to see if it leads to better weight loss and health outcomes.

Participants will:

Follow a calorie-restricted diet for the duration of the study Be assigned to either a meal replacement program or a standard diet Attend study visits for body measurements and blood tests Report their feelings of hunger and fullness

This randomized, controlled clinical trial is designed to evaluate the effectiveness of a structured, high-protein, calorie-restricted diet that includes standardized protein-based meal replacement products and additional dietary supplements in capsule form compared to a standard low-calorie diet in adults with overweight or obesity.

Approximately 60 participants aged 25 to 60 years will be enrolled and randomly assigned to one of two groups. The intervention group will follow a structured nutrition program that includes replacing two main meals per day with a protein-based meal replacement shake and taking additional dietary supplements in capsule form twice daily with snacks. The control group will follow a conventional calorie-restricted diet based on general nutritional recommendations without meal replacement products or additional dietary supplements.

Participants in both groups will follow individualized meal plans tailored to their caloric needs.

Daily energy intake in both groups will be approximately 1400-1600 kcal, with an estimated energy deficit of about 500 kcal. Protein intake is expected to be higher in the intervention group compared to the control group.

The primary outcomes of the study include changes in body weight, body mass index, and body composition assessed by bioimpedance analysis. Secondary outcomes include metabolic parameters such as glucose, insulin, and lipid profile, as well as subjective measures including hunger, satiety, and overall well-being.

Participants will attend scheduled visits for anthropometric measurements and laboratory testing. Safety will be monitored throughout the study, including vital signs and the recording of any adverse events.

Inclusion Criteria:

• Adults aged 25 to 60 years
• Overweight or obesity
• Ability to provide informed consent
• Willingness to follow a calorie-restricted diet program
• Willingness to comply with study procedures

Exclusion Criteria:

• Pregnancy or breastfeeding
• Women of reproductive potential who are not using reliable contraception during the study
• Severe or uncontrolled cardiovascular disease, including recent myocardial infarction or stroke within the past 6 months, unstable angina, or heart failure
• Uncontrolled arterial hypertension at screening
• Severe renal impairment
• Severe hepatic dysfunction
• Diabetes requiring insulin therapy or uncontrolled diabetes
• Active oncological disease or cancer treatment within the past 12 months
• Acute or chronic inflammatory disease in the acute stage
• History of gastrointestinal or bariatric surgery affecting absorption or body weight within the past 12 months
• Severe pulmonary disease in the stage of decompensation Allergy or intolerance to components of the study products, including milk proteins or lactose-containing products Current use of medications or dietary supplements that significantly affect body weight, if discontinuation before study start is not possible Participation in another interventional clinical study within the past 3 months Inability to provide informed consent or comply with the study protocol Significant body weight change, defined as more than 5% gain or loss, within the past 3 months before screening Severe psychiatric disorders or eating disorders that may interfere with participation Active alcohol or substance dependence Chronic use of systemic glucocorticoids or other medications affecting body weight, if discontinuation is not appropriate Planned pregnancy during the study period Uncontrolled thyroid disease Acute infection or febrile illness at screening Clinically significant abnormal laboratory findings at screening that, in the investigator's opinion, make participation unsafe

Individual participant data (IPD) will not be shared due to privacy and confidentiality considerations and the absence of a predefined data sharing plan.

This is an open-label study. Both participants and researchers are aware of group assignments.