DETERMINING WEIGHT AND BODY COMPOSITION

Some of the techniques used to determine overweight and obesity are common and routinely used by the general public.  Other are expensive and of limited availability.

Height-Weight Tables

Height and weight tables were originally developed in 1983 to assist people in determining the relationship between their weight and desirable standards.  Nearly over version of these tables has come under criticism for not considering variables such as gender, age, frame size, and body composition.  Some versions were thought to be too rigorous in establishing cutoff points for ideal or desirable weight, and others were deemed too generous.  Although still available, these tables are being gradually replaced by other assessment techniques.

Healthy Body Weight

You can determine your healthy body weight by using the weight guidelines found in the Dietary Guidelines for Americans.  This assessment involves converting two body measurements, the waist and the hip circumference, into a waist-to-hip ratio (WHR) that can then be applied to weight ranges for people with particular ages and heights.  An acceptable WHR, for women is near the lower end of each weight range, and for men it is at the higher end of each weight range.

To make a WHR determination, follow these steps:

1.       Measure around your waist near your navel while you stand relaxed (not pulling in your stomach).

2.       Measure around your hips, over the buttocks where the hips are largest.

3.       Divide the waist measurement by the hip measurement.

For example, a woman with a 25-inch waist and 36-inch hips has a WHR of less than .80 generally have a body weight that falls within the healthy range for their age and height; men with a WHR of less than .90 will also probably fall within the range considered healthy for their age and height.

This new system was developed because of the growing concern over the relationship between the amount of fat located around the waist, the spare tire, and the development of several serious health problems.  As a point of interest, the Dietary Guidelines for Americans do not use WHR as a clinical marker for the treatment of obesity;  instead they use only waist circumference.  The risk of health problems such as heart disease and diabetes increases at a waist measurement of 35 inches for women and 40 inches for men, regardless of height.

Body Mass Index

Another method for assessing healthy body weight is the body mass index(BMI).  BMI is calculated metrically as weight divided by height squared (kg/m²).  The BMI does not reflect body composition (fat versus lean tissue) or consider the degree of fat accumulated in the central body cavity.  It is, nevertheless, widely used in determining obesity.  Overweight is defined for women with a BMI over 27.3 and 27.8 for men.  Individuals are considered obese when BMI is 30.0 or above.  Severe or morbid obesity is when the BMI is greater than 40.

An alternative method of determining the BMI is to a nomogram.  Like the BMI, the nomogram requires information about both weight and height.

BOD POD (Body Composition System)

The newest method of determining body composition involves the use of the BOD POD, an egg-shaped chamber that uses computerized pressure sensors to determine the amount of air displaced by the person’s body (larger people displace more air than smaller people).  From this measure, you can then calculate the person’s body density and percentage of body fat.  Additional techniques in which highly accurate but expensive technology is used to determine body composition, including computed tomography (CT) scans, magnetic resonance imaging (MRI), infrared light transmission, and neutron activation, may become common ways of measuring body composition in the future.

Skinfold Measurements

Skinfold measurement are another way to measure body composition.  In this assessment procedure, constant pressure calipers are used to measure the thickness of the layer of fat beneath the skin’s surface, the subcutaneous fat layer.  These measurements are taken at key places on the body.  Through the use specific formulas, skinfold measurements can be used to calculate the percentage of body fat.  The percent body fat value can also be used in determining desirable body weight.  It should be noted that there are some drawbacks to this type of measure.  First, body fat calipers may require someone else to perform the test as it is sometimes difficult to get an accurate measurement on yourself.  Second, skinfolds are notoriously hard to locate precisely, and just a few millimeters off can make a significant difference.

Young adult men normally have a body fat percentage of 10% to 15%.  The normal range for young adult women is 22% to 25%.  When a man’s body fat is higher than 20% and a woman’s body fat is above 30%, they are considered to be obese.  The higher percentage of fat typically found in women is related to preparation to pregnancy and breastfeeding.

Hydrostatic Weighing

Hydrostatic (underwater) weighing is another precise method of determining the relative amounts of fat and lean body mass that make up body weight.  A person’s percentage of body fat is determined by comparing the underwater weight with the body weight out of water and dry.  The need for expensive facilities (a tank or pool) and experienced technicians makes the availability and cost of this procedure limited to small-scale application, such as a large research universities or teaching hospital.

Appearance

While it may seem as though the simplest method of determining one’s body size is to look in the mirror, for most people this is not an accurate measure.  Research shows that most women are dissatisfied with their appearance or body image and perceive themselves as needing to lose an average of 10-15 pounds when in actually they are in a healthy weight range.  Body dissatisfaction is endemic to young women in Western culture as evidenced by the rate of dieting in the United States, stating at a young age.  In fact, on any given day, 50% of 10 year old are on a diet, two-thirds of high school women, and a third of all adult women are dieting.  There is also an important difference between one’s internal concept of memory of one’s body and actual body perception, and this is particularly problematic for people with eating disorders.

Most people use scales to determine their weight, but scales can be highly inaccurate, as evidenced by weighing yourself on a variety of scales and weighing different amounts.  Also, you will probably weigh less in the morning when you first wake up and more in the evening, after having eaten during the day.  So if you are using a scale to monitor your weight, you need to do so on the same scale, at the same time of day, and with approximately the same weight of clothing.  Also, remember that muscle weighs more than fat, which explains why some toned and muscular athletes can weigh as much as someone who is sedentary and overweight.  In general, risk of disease increases with a higher percentage of body fat, not weight.

In extreme cases, a clinical condition referred to as “body dysmorphic disorder” (BDD) may develop.  BDD is a secret preoccupation with an imagined or slight flaw in one’s appearance.  Sometimes, people become almost completely fixated on concerns regarding body image, leading to repeatedly weighing themselves and checking in mirrors throughout the day, compulsive dieting and exercising, and undergoing cosmetic surgery.  These attempts to achieve the perfect body may lead to psychological dysfunction such as not wanting to leave the house because of imagined defects.