Don't confuse high protein competitive bodybuilding diets with the high protein diets advocated or opposed by certain doctors - the "experts" themselves! I am training for my first-ever bodybuilding competition for the Masters Ironman this year. A lot of factors fall into play: experience, knowledge, level of fitness, goals and individual body types of what works best and how much (protein, carbs, fat) is "absorbed" daily. Protein is primarily used to build, maintain and repair body tissues. But when it is consumed in high amounts when carbs become limited its secondary function becomes used (in conjunction with repairing body tissues) to provide energy and assist in the recovery process, second after carbs (your primary source of energy), to get more lean and hard for athletic competition readiness.