Protocol for the Popular Diets and Musculoskeletal Health in Aging (POPDIETS-AGING) Pilot Study

Objectives: Eucaloric very low carbohydrate ketogenic diets (KD) are therapeutic diets that generate ketones for metabolic fuel while meeting nutritional requirements. Preclinical data indicate KD may help to mitigate sarcopenia but adversely impact bone. Despite the important knowledge gaps, clinical trials of KD therapy have surged recently in adult medicine. Given the burden of musculoskeletal disease in older adults, it is vital to understand the effects of KD on the musculoskeletal system of older adults, to inform the benefit-risk assessment for an older patient. The objective of this study is to determine the feasibility of a randomized clinical trial to compare the effects of KD and a Mediterranean diet (MD) (as a standard of care comparator) on body composition and markers of bone health and muscle function in older adults. Methods: We will conduct a 2-arm parallel randomized clinical trial to study the feasibility of a 6-week intervention with either a KD or MD. Participants will be community-dwelling men and women aged ≥ 60 years with body mass index 20 to < 35 kg/m2 residing in North Central Florida. Test diets were formulated to optimize nutritional quality and minimize inadvertent differences in key nutrients that may impact physiological outcomes. Food will be provided to facilitate adherence. Primary outcomes include participant enrollment, retention, and adherence rates. Secondary outcomes include changes in body composition, bone turnover, and physical function. Results: Not applicable; protocol abstract. Conclusions: We expect our pilot study to demonstrate feasibility and to provide the information required to improve the rigor of a future clinical trial. The future trial will test whether a KD compared with MD improves skeletal muscle function but impairs bone turnover in older adults.