Plant-based Diet in Older People: What Consequences for Muscle Health?

This randomized, controlled, two-arm clinical study aims to determine how increasing the proportion of plant-based foods in the diet affects skeletal muscle strength, mass and function, protein metabolism, microbiota and key metabolic markers in healthy older men and women. We hypothesize that diets enriched with animal-based foods will maintain maximal quadriceps strength-the primary outcome of the study-more effectively after the 3-month nutritional intervention than plant-based diets. Proteomic analyses will be performed to identify molecular mechanisms and potential muscle biomarkers reflecting metabolic adaptations of skeletal muscle to plant-enriched diets. In addition, metabolic health markers and micronutrient status will be evaluated to better understand the overall health effects of dietary plant-based transition in older adults.

Inclusion Criteria: * Men and women aged 65 years and older * Body Mass Index (BMI) between 18.5 and 30 kg/m² (exclusive) * Physical activity ≤ 3000 MET-min/week, assessed using the ONAPS-PAQ questionnaire * Laboratory tests compatible with participation in the study * Adequate venous status, as assessed by study nurses, allowing catheter placement * Willingness to participate in study procedures, including indirect calorimetry, functional tests, and assigned dietary intervention (plant-enriched or standard diet) * Affiliation with the French Social Security system Exclusion Criteria: * Men and women aged 65 years and older * Body Mass Index (BMI) between 18.5 and 30 kg/m² (exclusive) * Physical activity \< 3000 MET-min/week, assessed using the ONAPS-PAQ questionnaire * Laboratory tests compatible with participation in the study * Adequate venous status, as assessed by study nurses, allowing catheter placement * Willingness to participate in study procedures, including indirect calorimetry, functional tests, and assigned dietary intervention (plant-enriched or standard diet) * Affiliation with the French Social Security system * Exclusion period from a previous study or total compensation exceeding €6,000 in the 12 months prior to study initiation (verified through the National Research Volunteer Database) * Patients under legal guardianship, curatorship, deprived of liberty, or under judicial protection * Claustrophobia