Stepping on the scale reveals weight in pounds, but weight alone offers little information about a woman's body. A woman who is 5 feet tall and weighs 150 lbs. has a vastly different body composition than a woman who weighs the same but is 5 feet 10 inches tall. Incorporating a measure of body fat---the percentage of the body that is fat---paints a much clearer picture of a woman's body composition.
Types of Body Fat
The CSGNetwork.com explains that humans have two types of fat in their bodies: essential and storage. These fats serve different function within the body.
The essential fat helps both immune and hormone systems function properly. This fat is stored in the body's heart, lungs, liver, bone marrow, kidneys, spleen, muscles, intestines and some other organs. Essential fat is gender specific; women carry this special fat in their hips, thighs, pelvis and breasts, and the fat is important for hormone function and childbearing. Essential fat is generally 10 to 12 percent of the total weight in women---four times the average amount in males. Having a lower percentage may jeopardize a woman's health.
Storage fat is the body's fuel. When a woman gains or loses weight, this fat increases or decreases. The average, nonathletic woman's storage fat totals about 15 percent of her body weight, according to CSGNetwork.com.
Calipers to Measure Fat
One method for calculating the percentage of body fat in a woman's body uses calipers to pinch the fat present in specific locations on the body, says Linear Software, a body fat analysis program producer. The calipers are held in place for 1 to 2 seconds and then a measurement in millimeters is taken and recorded. All measurements are taken from one side of the body, usually the right. Each measurement is taken at least twice to make sure the correct amount of fat is being pinched and the measurements are within 1 to 2 mm of each other.
On a woman's body, caliper pinches are taken and recorded on the chest; on the fold below the armpit; on the bicep; on the abdomen, 1 inch to the right of the bellybutton; on the suprailiac, which is a diagonal fold right above the iliac crest near the front of the woman's waist; on the thigh; on the calf; on the subscapular, which is below the shoulder blade; on the tricep; and on the lower back, directly over the kidneys. Family Education reports that when performed correctly, the caliper, or skinfold, method is within 3 percent accurate.
The measurements are placed into a program to calculate body fat percentage. Programs such as Composition Tracker, Linear's Body Tracker and Shareware Connection's free Desktop U.S. Army Body Fat % Calculator perform the calculations based on several methods and give a resulting percentage of body fat.
Other Fat-Measuring Methods
The caliper method is the most widely used fat-calculating method today because it can be done at home, in a physician's office or in a gym. Alternative methods, although sometimes more accurate, cost more and require expensive equipment.
The website Family Education describes the most accurate method as DEXA, a radiographic measurement similar to the one for bone density determination, which is performed in a doctor's office or radiology lab. Slightly less accurate is the water displacement method, requiring the person being measured to completely submerse herself in a special water tank.
The bioelectric impedance method, which uses a machine similar to a scale, is commonly found in gyms and even in homes, but it's unreliable, reports Family Education. The results depend on factors such as temperature, water weight, blood flow and electrolytes. This method is even more unreliable when measuring well-toned athletes with large muscle mass.
Body Fat Standards for Women
The American Council on Exercise body fat chart reports the following categories of body fat percentages for women: 10 to 13 percent body fat means the woman has "essential fat" only. Women who are categorized as "athletes" have 14 to 20 percent body fat. The level called "fitness" describes a woman with 21 to 24 percent body fat. The highest "acceptable" level of body fat is 25 to 31 percent. A body fat percentage of 32 percent or higher qualifies a woman as "obese."
Thus, the suggested healthy body fat percentage is 31 percent or less.
Body Fat's Effect
By knowing her body fat percentage, a woman gains a better perspective on her body's overall health. Body fat levels correlate directly with several diseases, including type 2 diabetes, heart disease, stroke and hypertension, reports the American Council on Exercise. If body fat percentages are too high, a woman should seek help to lower her body's fat percentage, and thereby lower her risk of health issues.
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