A bodybuilder is someone who trains intensely with weights and follows strict nutrition plans to develop unusually large, well-defined muscles. Unlike athletes who lift weights to get stronger for their sport, bodybuilders focus on making their muscles as big and symmetrical as possible, then display them in competitions where judges evaluate their muscular development, proportions, and poses.

Bodybuilders spend hours in the gym each week doing exercises like bench presses, squats, and curls, carefully working each muscle group. They eat large amounts of protein and monitor their diet with scientific precision, because building that much muscle requires very specific nutrition. Before competitions, they reduce body fat to extremely low levels so every muscle shows clearly.

The sport began in the late 1800s, and figures like Arnold Schwarzenegger made bodybuilding famous in the 1970s before he became a movie star. Today's competitive bodybuilders develop muscle mass far beyond what most people would ever want or need. Many regular people use bodybuilding techniques in modified form, lifting weights and eating protein to build some muscle and get stronger, without taking it to competitive extremes. That's sometimes called recreational bodybuilding.