Dietary patterns and decreased muscle strength incidence: findings from the Korean Genome and Epidemiology Study

Objectives: Muscle strength is a fundamental determinant of functional capacity across adulthood. While dietary protein has been widely studied, prospective evidence considering overall dietary patterns remains inconsistent. We examined the association between macronutrient-based dietary patterns and incident decreased muscle strength among adults aged 40 years and older. Methods: We analyzed 31,968 adults aged ≥40 years without decreased muscle strength at baseline from the Korean Genome and Epidemiology Study. The participants were categorized into four groups according to macronutrient energy proportions: high-carbohydrate, high-fat, high-protein, and normal diets. The incidence of decreased muscle strength was defined as <28 kg in men and <18 kg in women at follow-up. Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) of decreased muscle strength between groups, and linear mixed-effects models were used to evaluate longitudinal changes in handgrip strength, including time, group, and the group-by-time interaction. Results: During a median follow-up of 4.0 years, 2,194 participants developed incident decreased muscle strength (incidence rate 1.65 per 100 person-years). The high-protein dietary pattern was associated with a higher risk of incident decreased muscle strength compared with the normal diet (Adjusted HR 1.45, 95% CI 1.06−1.99), whereas no significant associations were observed for high-carbohydrate or high-fat dietary patterns. Changes in dietary patterns from baseline to follow-up were not significantly associated with the risk of decreased muscle strength, and the magnitude of change in handgrip strength over time did not differ across dietary pattern groups. Conclusions: In middle-aged and older Korean adults, the high-protein dietary pattern was associated with an increased risk of incident muscle strength decline compared to the normal dietary pattern, whereas high-carbohydrate and high-fat patterns were not. These findings suggest that a balanced macronutrient composition, rather than protein intake alone, may be relevant to muscle strength.