Macronutrient-Based Dietary Patterns and the Risk of Muscle Mass Decline in Middle-Aged and Older Adults: A...

Background/Objectives: Loss of skeletal muscle mass is linked to functional decline and adverse health outcomes. Evidence on long-term associations between macronutrient-based dietary patterns and muscle mass decline remains limited. This study examined this association in a prospective cohort of Korean adults aged 40-69 years. Methods: Participants were categorized into four groups by macronutrient energy proportion: high-carbohydrate (HCHO, carbohydrate > 65% of total energy), high-fat (HF, fat > 30%), high-protein (HP, protein > 20%), and normal diets (ND). Cox models estimated associations between dietary patterns and decline in height-adjusted skeletal muscle mass, including sensitivity analyses using stricter decline thresholds (≥3%, ≥5%, and a reduction exceeding the least significant change); linear mixed-effects models evaluated longitudinal muscle mass changes. Results: A total of 9516 adults were included. During a median follow-up of 5.6 years (IQR 3.8-9.8), 6971 participants developed a decline in skeletal muscle mass relative to baseline. Adjusted hazards were higher for HCHO (aHR 1.12, 95% CI 1.04-1.21) and HP (aHR 1.20, 95% CI 1.01-1.42) versus ND, whereas HF showed no significant association (aHR 0.73, 95% CI 0.46-1.15). These associations were attenuated and no longer significant under stricter thresholds. Mixed-effects models showed no significant group effects or group-by-time interactions. Conclusions: HCHO and HP patterns were associated with a higher risk of muscle mass decline, but this was not consistent under stricter thresholds, and longitudinal trajectories did not differ across patterns. These findings should be considered preliminary. Further studies should clarify the roles of macronutrient quality, food sources, and overall dietary patterns in muscle health.