We used a randomized crossover design whereby @ healthy women -LSB- mean SD age : @ @ y ; mean SD body mass index ( in kg/m ( @ ) ) : @ @ -RSB- followed two @-d fully controlled dietary interventions involving consumption of either a low-protein diet ( @ g protein kg body weight ( -@ ) d ( -@ ) , ~ @ % of energy derived from protein , approximately half the normal protein intake ) or a high-protein diet ( @ g protein kg body weight ( -@ ) d ( -@ ) , ~ @ % of energy , approximately twice the normal intake ) .