Understanding Body Composition

The incidence of obesity is growing in the United States . Obesity is 5 to 8 times more common among Americans today than it was at the start of the twentieth century. Thirty-four million Americans are overweight (approximately 15 million men and 19 million women).

As stated in an earlier unit, personal trainers have more time with the apparently healthy population than do physicians. They have a tremendous influence on shaping the health attitudes and practices of those around them. Therefore they must possess a solid foundation of scientific principles – such as understanding body composition assessment – and be able to apply these principles.

In order to assist your clients in reaching their fitness related goals, we need to know more information on the current standards for body composition categorization and assessment. We will begin by discussing body types, BMI, waist circumference and conclude with methods for body fat determination.

Body Types (Somatotype)

The way your body looks is a result of your genetics and environmental factors (such as training and nutrition). The genetic factor has a dominant influence on your body structure, both inside and out. Scientist W. H. Sheldon devised a system of classifying different human body types. He called this system “somatotype.” Using this system, humans can be classified in three body types:

  • Mesomorphic or muscular body type.
  • Ectomorphic or slim, linear body type.
  • Endomorphic or fat, round type.

Sheldon’s system uses a somatotype number with three digits on a scale of 1 to 7. The first digit refers to the degree of endomorphy, the second digit refers to the degree of mesomorphy, and the third digit refers to the degree of ecotmorphy. An extreme endomorph has the somatotype 711, an extreme mesomorph has the somatotype 171 and an extreme ectomorph has the somatotype 117.

Most individuals have a dominant somatotype and also display some characteristics of the other two. An average person may fall somewhere around a 333 or a 444 rating. This system is useful because it helps understand genetic predisposition. For example, on a pound-for-pound bodyweight basis, ectomorphs usually require more calories. Mesomorphs are next in line, and endomorphs require the fewest calories. Determined, competitive athletes should have their somatotypes determined by trained individuals. Elite, world-class athletes usually have a mesomorphic rating of 5 to 7 , endomorphic of 1 to 3 and ectomorphic rating of 4 to 1. This indicates that being predominantly mesomorphic is a common trait of elite athletes. This makes sense, as mesomorphs have a higher body composition of muscle mass, which is the primary tissue responsible for athletic performance. This does not mean that ectomorphs or endomorphs cannot become superior athletes; however, they should use training and nutrition methods to build more muscle mass and keep percent body fat within desirable levels for their sex and sport.

While it is good to know Sheldon’s system for academic purposes, we do not feel that it should be used as a factor or reference for program development. Genetic categorization diminishes the personal empowerment that is necessary for success. It is not possible to establish the relative portion of an individual’s health or fitness that is determined through heredity; therefore, genetic background neither dooms nor guarantees success in achieving and maintaining total fitness.

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