Body Composition is the technical term used to describe the different components that, when taken together, make up a person's body weight. Now one must keep in mind that body composition and body weight are two entirely different concepts, and they are not interchangeable. The human body is composed of a variety of different tissue types. The so-called 'lean' tissues, such as muscle, bone, and organs are metabolically active, while adipose, or fat tissue, is not. Adipose tissue is divided into three different categories : Essential fat, which supports life, and is extremely important to normal bodily function ; Storage fat, which protects internal organs and supplies some energy requirements ; Non-essential fat, serves no real purpose, and may, in fact, be detrimental to health. The difference in these tissues is not readily distinguishable by stepping on a scale. A scale simply takes the sum of everything (fat, muscle, water, hair…etc), and gives an absolute weight measurement. Scales can't determine the lean-to-fat ratio of that weight. An individual can be "over-weight" and not "over-fat." A bodybuilder, for example, may be 8% body fat, yet may be considered "over-weight" by a typical height-weight chart. Therefore, these charts are not a good indication of a person's ideal body weight for optimal health, much less for athletic performance. In order to identify these tissues, several different methods of assessing the percent of fat vs. lean mass of an individual have been developed. These methods are referred to as Body Composition Analysis.