I can’t say this any better than Mauro G. Di Pasquale, who is becoming a hero of mine.
However, for those athletes involved in strength events such as the Olympic field and sprint events, those in football or hockey, or weightlifters, powerlifters, and bodybuilders, I recommend between 1.2 and 1.6 g of high-quality protein per pound of total body weight. That means that if you weigh 200 lb and want to put on a maximum amount of muscle mass, then you will have to take in as much as 320g of protein daily. There are several competitive weightlifters, powerlifters, and bodybuilders that I know who take in 2-3 g of high-quality protein per pound of body weight.
If you are trying to lose weight or body fat it is important to keep your dietary protein levels high. That is because the body oxidizes more protein on a calorie-deficient diet than it would in a diet that has adequate calories. The larger the body muscle mass, the more transamination of amino acids occurs to fulfill energy needs. Thus for those wishing to lose weight but maintain or even increase lean body mass in specific skeletal muscles, I recommend at least 1.5g of high-quality protein per pound of body weight. The reduction in claories needed to lose weight should be at the expense of the fats and carbohydrates, not protein (345).