PREPARATION FOR % BODY FAT SCREENING
(For an appointment, call x2081. For more info, call Bob Weathers x 2082)
Please understand that there is no single method of body fat measurement known to have perfect validity for everyone. The best method for one individual may be among the least valid tests for other people. In fact, underwater weighing (the method that most people consider to be a "gold standard") MAY have as much as 5% body fat error (we hope <3%) when used to estimate the fatness of SOME people.
Since all methods of assessment provide ESTIMATES rather than direct measurement, and because the validity of methods varies with the individual being tested; use of multiple methods is likely to provide more meaningful information than is a single assessment. We commonly use a combination of skinfold and bio-electrical impedance analysis in the SPU Exercise Science Lab, but we can also perform underwater weighing and other measurements as desired.
The amount and nature of body water affects the validity of most techniques (especially bio-electrical impedance analysis). For this reason, the following guidelines should be followed in preparation for assessment:
Please report to the Exercise Science Lab having adhered to these guidelines and understanding that ESTIMATIONS of percent body fat are all that we (or anyone else) can provide. Your estimated body fatness can be compared with norms, but we cannot say with great confidence what amount or percent is ideal for you. The "healthy" ranges for %fat are USUALLY 17-32 and 10-25 for females and males respectively. However, healthy active people may have less fat.
You should be aware of the fact that, while the medical/scientific community seems to agree that excessive fat is more hazardous than excessive weight, there is little evidence linking percent fat to health problems. The vast majority of studies on the topic have simply used body mass index (BMI) rather than estimating percent fat, and BMI's less than 25 kg/m2 are generally considerd to be "healthy." Recently, several researchers have reported that DISTRIBUTION of fat is more important than either fatness per se or BMI, and abdominal fat seems to be much more hazardous than fat in the hips or thighs. Waist circumference, waist diameter, and the ratio of waist to hip circumference are generally considered to be sensitive indicators of fat-related health. It I now widely recommended that this ratio should be no higher than 1.0 in males and 0.8 in females.
It may be very important to note that some recent research suggests that the real problem may be the lifestyle (poor dietary and exercise habits) normally associated with obesity rather than fatness itself. We would encourage the adoption of a pattern of health-enhancing nutrition and physical activity-regardless of the results of your percent body fat screening.
Please bring this form with you to the Exercise Science Lab, having decided which of the methods of assessment you desire from those described on the back of this sheet.
Appointment Date ___________ Time __________
Age______ yr Height _______ in Weight _________ lb
Waist Circumference _______ Hip Circumference _______ Waist/Hip _______
Bio-Electrical Impedance Analysis is performed by attaching small adhesive electrodes to your right foot, ankle, hand, and wrist and measuring the resistance your body tissues present to a harmless 50 kHz current. This resistance (or impedance) is related to the amount of electrolytes, water, and lean tissue you have. Based on assumptions about how much lean tissue you have, fat weight and percent fat can be calculated. This technique is fast (< 5 min), extremely simple, totally painless, and valid for most people who CAREFULLY FOLLOW the instructions given earlier and for whom we can find an appropriate formula.
Resistance = _______ohms Estimated Fat = _______ %
Skinfold Measurement involves use of special calipers to determine the thickness of subcutaneous fat (deposits just below the skin) at various sites on the body. This technique assumes that the sites measured are representative of all of the body's subcutaneous fat and that subcutaneous fat is about 50% of the body's total fat. Both of these assumptions vary in validity from individual to individual, but the technique is simple, fast (5-10 min), usually painless, and apparently as valid as any other technique for most people. Validity often increases with the number of sites being measure, and we will MINIMALLY need to have access to:
Females-back of upper arm, top/front of pelvis, and thigh.
Males-chest, abdomen, and thigh
Sum of _______Skinfolds = ___________mm Estimated fat = _________%
Diameter and Circumference Measurements can be taken at a variety of sites on the body. Bone diameters indicate differences in skeletal size (which skinfolds do not), but circumference measurements cannot distinguish between fat and other types of tissue. While inexpensive, simple, and fairly fast (5-10 min); these techniques are not generally as valid as other methods. However, validity is improved as more sites are measured.
Estimated Fat _________ %
Underwater (Hydrostatic) Weighing allows an indirect determination of body volume and density. Then, since we know that body tissues vary in density (and that fat floats), body fatness can also be estimated. This method is generally believed to provide the most valid estimate of body fatness, and that is possibly true when lung volumes are actually measured rather than simply predicted during underwater weighing, and when the most appropriate equations are used to estimate body fatness from the calculated body density. However, when lung volumes are only estimated, other techniques may be as (or even more) valid. Underwater weighing requires 30-45 minutes with lung measurement and 10-20 minutes without it.
Body Density _______g/mL Estimated Fat _________%
Fitness Classification by Percent of Body Weight that is Fat
(Low fatness is associated with high fitness)
FEMALE MALE
AGE HIGH AVG. LOW HIGH AVG. LOW
18-21 <18.1 24.3-21.4 >28.1 <5.9 10.7-8.3 >14.4
20-29 <17.1 23.7-20.6 >27.7 <9.4 17.4-14.1 >22.4
30-39 <18.0 24.9-21.6 >29.3 <13.9 20.5-17.5 >24.2
40-49 <21.3 28.1-24.9 >32.1 <16.3 22.5-19.6 >26.1
50-59 <25.0 31.6-28.5 >35.6 <17.9 24.1-21.3 >27.5
60+ <25.1 32.5-29.3 >36.6 <18.4 25.0-22.0 >28.5