Modern bodybuilders understand that resting the muscles is important.
They focus on one muscle group per workout, once a week. All muscles get some work during any training session, but they are trained heavily only once per week in their specific focus session. Natural muscle growth is spurred by this approach.
The modern athlete eats a balanced diet of proteins, fats, complex carbohydrates and lots of water.
They also take natural supplements to augment their diet and to aid in the metabolizing of protein. Most of them eschew artificial chemical enhancements like anabolic steroids, human growth hormone and stimulants.
The modern bodybuilding world now has two approaches to contests; those where there is no regulation on how muscle size was achieved and the “natural” events where the contestants are tested for banned substances like steroids and HGH.