Effects of Three Dietary Strategies on Body Composition and Metabolic Health in Adults With Overweight or Obesity

Detailed Description:

This randomized, controlled, parallel-group pilot clinical trial will evaluate the effects of three different hypocaloric dietary strategies on body composition, metabolic markers, and metabolic syndrome remission in adults with overweight or obesity.

Background and Rationale Overweight and obesity are highly prevalent in Europe and are associated with an increased risk of metabolic syndrome, cardiovascular disease, type 2 diabetes, and obesity-related cancers. Dietary interventions are a cornerstone in their management, but the optimal macronutrient composition for improving short-term metabolic outcomes remains unclear. This study investigates the comparative impact of a traditional Mediterranean diet, a Mediterranean low-carbohydrate diet, and a high-protein diet over a 12-week period.

Study Design A total of 45 participants aged 18-65 years with a body mass index (BMI) ≥25 kg/m² will be recruited through online advertisements and primary care referrals. After eligibility screening and informed consent, participants will be randomly allocated (1:1:1) to one of the three dietary intervention arms.

Intervention

All diets will be hypocaloric, aiming for a 20-25% reduction in individual energy requirements, and will differ in macronutrient distribution:

Mediterranean diet: 55% carbohydrates, 15% proteins, 30% fats.

Mediterranean low-carbohydrate diet: 40% carbohydrates, 25% proteins, 35% fats.

High-protein diet: 30% carbohydrates, 40% proteins, 30% fats.

Participants will be followed biweekly by qualified dietitians through in-person or phone consultations. They will receive personalized meal plans, nutritional education, and support materials to enhance adherence.

Assessments Anthropometric measures (BMI, fat mass, fat-free mass, waist and hip circumference) will be obtained at baseline and at 12 weeks using standardized protocols and validated equipment. Blood pressure will be measured with a calibrated automated device after a seated rest. Fasting blood samples will be collected in the morning for biochemical analyses, including glucose, HbA1c, insulin, lipid profile, uric acid, iron status, high-sensitivity C-reactive protein, fibrinogen, erythrocyte sedimentation rate, and liver enzymes.

Outcomes The primary outcome is the change in BMI after 12 weeks. Secondary outcomes include changes in body composition, metabolic and inflammatory biomarkers, and the proportion of participants meeting the International Diabetes Federation (IDF) criteria for metabolic syndrome at baseline and post-intervention.

Ethics and Dissemination The study protocol was approved by the Ethics Committee of Aragón (CEICA) (No. 13/2024) and will be conducted in accordance with the Declaration of Helsinki and current regulatory requirements. The findings will be disseminated through peer-reviewed publications and conference presentations.

Inclusion criteria

• Adults aged 20-70 years
• Body mass index (BMI) ≥ 25 kg/m² (overweight or obesity)
• Stable body weight (± 2 kg) in the last 3 months prior to screening
• Willingness to follow one of the prescribed dietary interventions for 12 weeks
• Ability to attend scheduled follow-up visits and complete study assessments
• Provided written informed consent prior to study participation

Exclusion criteria

• Diagnosis of type 1 diabetes, cardiovascular disease, cancer, chronic kidney disease, liver disease, or other serious chronic conditions that could interfere with the intervention
• Pregnancy or breastfeeding
• Current participation in another clinical trial
• History of bariatric surgery or weight-loss program within the past 6 months
• Use of medications known to affect body weight, metabolism, or appetite (e.g., glucocorticoids, weight-loss drugs, antipsychotics)
• Any food allergy or intolerance that would preclude adherence to the assigned diet
• Alcohol or substance abuse
• Any condition or circumstance that, in the opinion of the investigators, would make the participant unsuitable for the study