21 Body Mass Index

Body Composition

Let’s revisit Jolene, who works as a registered nurse (RN) on the medical/surgical (MED) floor of a large hospital. An important part of Jolene’s job is patient education and on MED floor much of that education relates to healthy nutrition and body composition. Body composition attempts to quantify the relative amounts of different tissue types present in a person’s body, typically with emphasis on ensuring a healthy amounts of fat relative to other tissues[1]. Body composition is just one of many measurable factors that health professionals use to evaluate a person’s overall health and assess risk for type II diabetes, cardiovascular disease, sleep apnea, osteoarthritis, osteoporosis, and other medical conditions.

Body Mass Index

The body mass index (BMI) attempts to categorize body composition using only height and weight as inputs. Health professionals like Jolene understand that the BMI can be useful when paired with other evaluations, but that it has many limitations when applied to individuals or very specific populations. For example, the extra weight caused by having more than average muscle can result in a false unhealthy weight categorization. [2]. Additional methods for determining body composition include bioelectric impedance, anthropometric, DEXA scan, hydrostatic weighing, and the skin fold method, which we will investigate in the following sections.[3]



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