Physical education and BMI calculations

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BODY COMPOSITION TESTSSkinfold Measurement · description / procedure: Estimation of body fat by skinfold thickness measurement. Measurement can use from 3 to 9 different standard anatomical sites around the body. The right side is usually only measured. The tester pinches the skin at the appropriate site to raise a double layer of skin and the underlying adipose tissue, but not the muscle. The calipers are then applied 1 cm below and at right angles to the pinch, and a reading taken 2 seconds later. The mean of two measurements should be taken. If the two measurements differ greatly, a third should then be done, then the median value taken.· the sites: the following descriptions are for the common sites at which the skinfold pinch is taken. The caliper is then applied 1 cm below and at right angles to the pinch. I have added some lay terms (in brackets) that may help the non-medical users to find the correct sites for taking the skinfold measurements.TRICEPS A vertical pinch at the level of the mid-point between acromial process (boney tip of shoulder) and proximal end of the radius bone (elbow joint), on the posterior (back) surface of the arm.
BICEPS The pinch position is at the same level as for triceps, though on the anterior (front) surface of arm.
SUBSCAPULA The pinch is made 2 cm below the lower angle of the scapula (bottom point of shoulder blade) on a line running laterally (away from the body) and downwards (at about 45 degrees). The fold is lifted in this direction.
AXILLA The pinch is made at the intersection of a horizontal line level with the bottom edge of the xiphoid process (lowest point of the breast bone), and a vertical line from the mid axilla (middle of armpit).
ILIAC CREST The pinch is made at a site immediately above the iliac crest (top of hip bone), at the mid-axillary line. The fold is directed anteriorly and downward.
SUPRASPINALE The pinch is made at the intersection of a line joining the spinale (front part of iliac crest) and the anterior (front) part of the axilla (armpit), and a horizontal line at the level of the iliac crest. The pinch is directed anteriorly and downward
ABDOMINAL The vertical pinch is made 5 cm adjacent to the umbilicus (belly-button)
FRONT THIGH A vertical pinch is made at the mid-point of the anterior surface of the thigh, midway between patella (knee cap) and inguinal fold (crease at top of thigh).
MEDIAL CALF A vertical pinch is made at the point of largest circumference on medial (inside) surface of the calf.
CHEST A diagonal pinch is made between the axilla and nipple as high as possible on the anterior axillary fold (males only).
· results: Because of the increased errors involved, it is not appropriate to convert skinfold measures to percentage body fat (%BF). It is best to use the sum of several sites to monitor and compare body fat measures. In order to satisfy many of you who want a percentage body fat measure, I have included a couple of equations for calculating this. There are hundreds of equations available, and it is best to use one that is based on a sample that most closely resemble you. Use them at your own risk. You will find that you get different results depending on which equation you use.Some of the following equations give a measure of body density (D), which then needs to be converted to %BF using the Siri equation: %BF = (495/D) - 450. MALES: D = 1.10938 - (0.0008267 x sum of chest, abdominal, thigh) + (0.0000016 x square of the sum of chest, abdominal, thigh) - (0.0002574 x age), based on a sample aged 18-61. Jackson, A.S. & Pollock, M.L. (1978) Generalized equations for predicting body density of men. British J of Nutrition, 40: p497-504. D = 1.1043 - (0.001327 x thigh) - (0.00131 x subscapular), based on a sample aged 18-26. Sloan AW: Estimation of body fat in young men., J Appl. Physiol. (1967);23:p311-315. %BF = (0.1051 x sum of triceps, subscapular, supraspinale, abdominal, thigh, calf) + 2.585, based on a sample of college students. Yuhasz, M.S.: Physical Fitness Manual, London Ontario, University of Western Ontario, (1974). FEMALES: D = 1.0994921 - (0.0009929 x sum of triceps, suprailiac, thigh) + (0.0000023 x square of the sum of triceps, suprailiac, thigh) - (0.0001392 x age), based on a sample aged 18-55. Jackson, et al. (1980) Generalized equations for predicting body density of women. Medicine and Science in Sports and Exercise, 12:p175-182. D = 1.0764 - (0.0008 x iliac crest) - (0.00088 x tricep), based on a sample aged 17-25. Sloan, A.W., Burt A.J., Blyth C.S.: Estimating body fat in young women., J. Appl. Physiol. (1962);17:p967-970. %BF = (0.1548 x sum of triceps, subscpular, supraspinale, abdominal, thigh, calf) + 3.580, based on a sample of college students. Yuhasz, M.S.: Physical Fitness Manual, London Ontario,University of Western Ontario, (1974). · equipment required: skinfold calipers (e.g. Harpenden, Holtain, Slimglide, Lange). These should be calibrated for correct jaw tension and gap width. · target population: suitable for all populations, though it is sometimes difficult to get reliable measurements with obese people.· validity: using skinfold measurements is not a valid predictor of percent body fat, however they can be used as a monitoring device to indicate changes in body composition over time.· reliability: can vary from tester to tester depending on the skill and experience of the tester.· advantages: Skinfold measurements are widely utilised to assess body composition. It is a lot simpler than hydrostatic weighing. After the outlay for callipers, the tests costs are minimal.
Simple Skinfold Caliper
A Simple Caliper is a device which measures the thickness of a fold of skin with its underlying layer of fat. By doing this at key locations, shown by research to be representative of the total amount of fat on the body, it is possible to estimate the total percent bodyfat of a person. This inexpensive caliper is a simple device that can be a valuable tool in monitoring body fat increases and decreases. It requires a certain familiarity with the caliper method of body fat measurement. Instructions Included
Waist to hip ratio:
BODY COMPOSITION TESTS
Waist to Hip Ratio
· description / procedure: A simple calculation of the measurements of the waist girth divided by the hip girth.
· scoring: The table below gives general guidelines for acceptable levels for hip to waist ratio. You can use any units for the measurements (e.g. cm or inches), as it is only the ratio that is important.
acceptable unacceptable
excellent good average high extreme
male < 0.85 0.85 - 0.90 0.90 - 0.95 0.95 - 1.00 > 1.00
female < 0.75 0.75 - 0.80 0.80 - 0.85 0.85 - 0.90 > 0.90
· equipment required: tape measure
· target population: This measure is often used to determine the coronary artery disease risk factor associated with obesity.
· advantages: A simple measure that can be taken at home by people to monitor their own levels.
· other comments: The basis of this measure as a coronary disease risk factor is on the assumption is that fat stored around the waist poses a greater risk to health than fat stored elsewhere.
BODY COMPOSITION TESTSBody Mass Index (BMI)BMI stands for Body Mass Index. It takes a person's weight in kilograms and divides it by their height in meters squared. For instance, if your height is 1.82 meters, the divisor of the calculation will be (1.82 * 1.82) = 3.3124. If your weight is 70.5 kilograms, then your BMI is 21.3 (70.5 / 3.3124) (see calculator links below). The higher the figure the more overweight you are. Like any of these types of measures it is only an indication and other issues such as body type and shape have a bearing as well. Remember, BMI is just a guide - it does not apply to elderly populations, pregnant women or very muscular athletes. Calculate your own BMI! If you are from the US, use this calculator. For the rest of the world, there is a metric version. Test Details· description / procedure: BMI is calculated from body mass (M) and height (H). BMI = M / (H x H), where M = body mass in kilograms and H = height in meters. The higher the score usually indicating higher levels of body fat· scoring:underweight <20
healthy range 20-25
overweight 25-30
obese >30
· equipment required: scales and stadiometer as for weight and height.· target population: BMI is often used to determine the level of health risk associated with obesity.· advantages: simple calculation from standard measurements· disadvantages: BMI can be inaccurate, for example with large and muscular though lean athletes scoring high BMI levels which incorrectly rates them as obese.· other comments: Other measures of body composition would be preferable if available.
Does It Matter If You Are Overweight?
(c) Kim Beardsmore
Everywhere we look in the western world we are inundated with pictures, images, icons and inferences of the 'perfect' female shape! The truth is that many of these images are altered or enhanced in some way and do not depict the typical female form. The pressure to lose weight is immense when we are bombarded every day with media selling products based on slimness, sex appeal and fashion. The constant message is that slimness will make you desirable.
With the current demographic trends in western countries, and faced with a sea of high fat, high sugar combined with physical inactivity; it is time to pay attention to our weight but not for any reasons of desirability. The most important reason for wanting to be a healthy body weight is for health rather than for how your body looks.
Overweight and obesity are major public health problems in western countries. Since the 1980s both adult men and women have become heavier, with obesity rates more than doubling in the last 20 years! Children are also becoming heavier. There is a growing concern that we are inadvertently training our overweight children to become obese adults. It has been said, we are digging our graves with out teeth! So just why should we be concerned with achieving a healthy body weight?
Overweight linked with diabetes.
In January 2003, the Journal of the American Medical Association featured two studies that highlighted the topic of obesity and its impact on health. The first study focused on the relationship between obesity and diabetes, as well as the growing concern of diabetes in the U.S. between the years 2000 and 2001. The numbers don't look good, with an alarming 5.6% increase of obesity in both men and women-from all ethnic groups, age ranges and educational levels. The occurrence of diabetes also increased-up 8.2% from 2000.
Overweight linked with premature death.
The second study found that obesity appears to markedly lessen life expectancy, especially among young adults. The researchers compared Body-Mass Index (BMI) to longevity and found a correlation between premature death and higher BMIs. For example, a 20-year-old white male, 5'10" weighing 288 pounds with a BMI of greater than 40 was estimated to lose 13 years of his life as a result of obesity. Findings were similar for women with higher BMIs, who were estimated to lose an average of eight years. While these studies reference extreme levels of obesity, there are still millions of overweight people in developed countries with a life expectancy rate that is three to five years less than their healthy-weight counterparts.
Overweight linked with heart disease.
Overweight people tend to have higher blood pressure and higher blood cholesterol, which are major risk factors for heart attack and other blood vessel disease. Being overweight can contribute to problems in the joints, and is also associated with other serious diseases such as diabetes.
How you tell if you are overweight
As we are all different shapes and sizes, there is not one recommended weight for your height. Instead there is a range of weights that are healthy for your height. One way to check your weight is to calculate your Body Mass Index or BMI.
Your BMI is a ratio or comparison of your height and weight expressed in a number. To find out your BMI you need to divide your weight (measured in kg) by your height (measured in m) squared. If you do not know your measurements in the metric system you can find any number of BMI calculators online that will do the conversion for you into empirical measures. One such calculator is at the website listed below.
The accepted definitions of weight categories by BMI are:
· Underweight - BMI less than 18.5
· Healthy weight - BMI between 18.5 and 24.9
· Overweight - BMI equal to or greater than 25 and up to 29.9
· Obese - BMI equal to or greater than 30
These BMI values only apply to adults aged 18 years and over and are based on studies of Caucasian populations. Therefore, they are not applicable to children and adolescents and they may not be appropriate for people of other cultural backgrounds.
Another way to check your weight is to measure your waist circumference, using a tape measure. This gives you an idea of whether you have a lot of fat stored around your middle. Waist circumferences associated with increased health risk are:
For men Waist circumference greater than 94cm
For women Waist circumference greater than 80cm
Being a healthy weight can help:
· improve blood cholesterol levels, blood pressure and blood glucose levels
· reduce your risk of other health related problems
· improve self confidence and self esteem
· make it easier to be physically active.
If you are obese or overweight...try not to gain additional weight. This will help you in years to come as people tend to increase weight with age. Better still look after your body and follow a healthy lifestyle incorporating a nutritious, delicious, health enhancing weight loss program. Just by losing 10 pounds you can significantly improve your overall health.
Body mass index charts of Men
A chart showing the Body Mass Index of Adult men, at various ages. It's not something you see every day. So what does it mean? What's interesting? You can Calculate your BMI result here.

Notice the 50th percentile Red line, which indicates the "median" BMI value. Compare it to a BMI of 25, which the CDC defines a "Overweight". You'll see that over 50 percent of American Men have a BMI over 25.
Also notice that Men's body mass index gradually increases with Age, until after age 50 to 60, when a gradual decline occurs. Each percentile line has a curved shape, even for skinny people at 25th and 10th percentiles. I believe this shows that it is "natural" for some weight gain to occur during adult life.
The chart shows how older children's (boys) BMI increases up to age 20, (and keeps on increasing after that). This data came from the standard CDC growth charts. There is a gap between the children's and adults data, because the data sources are different. The adult data (from the NHANES III survey) comes from recent data ( 1988-1994 ) whereas the CDC body-mass-index-for-age charts are derived from a mix of data from new and older sources.
For comparison purposes, this page (below) also shows a Women's body mass index chart. Do you notice a few differences between men and women? At less than 50th percentile, men have a higher BMI than women, likely because men tend to have more skeletal muscle mass. But after age 30, for the 50th percentiles or higher, women have a higher BMI level at each percentile line.

The table below shows actual numbers for median Body Mass Index of American men.
The "National Average" Median Body Mass Index values for Men:
Age: 20-29 yrs 30-39 yrs 40-49 yrs 50-59 yrs 60-69 yrs
Median BMI: 24.5 25.9 26.8 27.2 27.0
Formula for Body Mass Index: BMI
To calculate your Body Mass Index, take your weight (in kilograms),
and divide by your height (in meters) squared.
( Need a calculator? Duh.. use the body mass index BMI calculator,
which coincidentally, will convert units from imperial to metric and back)
( or, for an interesting diversion...
Click here to learn about Ideal Body Weight formulas. )

Who decided the Body Descriptions? What is overweight?
by Steven B.Halls, MD
A Body Mass Index between 25 and 29.9 is "overweight", ...