Final answer:
Whey protein concentrate must contain between 29% and 89% protein by weight, useful for bodybuilders in muscle recovery due to its amino acid content.
Step-by-step explanation:
By definition, whey protein concentrate contains at least 29% protein and no more than 89% protein by weight. Whey protein concentrate, which is derived from the process of making cheese from milk, falls within this range and is popular among bodybuilders for its high levels of essential amino acids and branched-chain amino acids. These nutrients are crucial for muscle recovery post-workout. There are different forms of whey protein, with whey isolate and whey hydrolysate being the other common forms; whey isolate consists of 90% or more protein by weight, and whey hydrolysate is pre-digested for fast absorption.