The effects of increased dietary protein on resistance training (RT)-induced changes in body composition and skeletal muscle fiber size are uncertain in older people.

We hypothesized that the ingestion of more animal-based foods, especially eggs, to achieve a higher protein intake would enhance RT-induced changes in body composition.

West Lafayette, IN.

36 older people (age 61±1 y; mean ± SEM).

Subjects completed RT three d/wk for 12 weeks, and consumed omnivorous diets that contained either 0.9±0.1 (lower protein) or 1.2±0.0 (higher protein) g protein·kg⁻¹·d⁻¹ (12±3 and 17±5 % of energy intakes, respectively), with the higher protein intake achieved by consuming more eggs, meats, and dairy foods. The lower and higher protein diets contained 213±21 and 610±105 mg cholesterol/d, respectively.

Strength, body composition, serum lipid-lipoprotein profile, urinary creatinine, skeletal muscle fiber type and size.

Among all subjects, over time (i.e. with RT) body weight was unchanged, lean mass (1.1±0.2 kg) increased, and fat mass (−1.4±0.2 kg) decreased (all changes P<0.05). Regional (i.e. trunk, legs, arms) lean mass increased and fat mass decreased. Whole body muscle mass (24-h urinary creatinine excretion) increased, but skeletal muscle (vastus lateralis) type 1, type 2a, and type 2x fiber cross-sectional areas did not change from baseline. Serum total and LDL cholesterol decreased (P<0.05) and HDL cholesterol and triacylglycerol were unchanged. Dietary protein and cholesterol intakes did not influence these responses to RT.

Consumption of diets that contained moderately higher protein and variable amounts of cholesterol did not differentially affect body composition, skeletal muscle fiber size, or serum lipid-lipoprotein profile responses to resistance training in older people.