What does 'percent body fat' refer to?

Percent body fat specifically refers to the proportion of fat mass relative to total body weight. This measurement provides insight into an individual's composition, indicating how much of their body weight is made up of fat as opposed to lean body mass, which includes muscle, water, and bone. Understanding percent body fat is vital for evaluating health risks—higher levels of body fat can be associated with various health issues, while lower levels might indicate a healthier body composition.

In contrast, the other options measure different components of body composition. The amount of water in the body pertains to hydration levels, muscle mass refers to lean tissue contributing to strength and metabolism, and bone density relates to the strength and structure of bones. Each of these factors plays a role in overall health but does not specifically measure the proportion of body fat.