Weight and Percent of Body Fat for Women

Weight and BMI

Three values are commonly used to measure your body composition. Weight, the most common standard, is cheap, convenient, and fairly reliable, although it can fluctuate up to five pounds with body fluids. Weight and height are used to calculate the Body Mass Index (BMI), another common term. This differs only from weight in that it adjusts for height; BMI also varies with body fluids. BMI, measured in kilograms per meters squared, is an unreliable guideline; standards usually do not differentiate between men and women or allow for the difference in muscle or fat content. In athletic women, BMI is especially inaccurate because muscle weight is heavier than fat weight, making you seem "fat" by BMI standards. Essentially, Body Mass Index is a number value that has replaced height and weight charts. The number is even more confusing because the recommended numbers are similar to but slightly different from body fat percent. According to standard guidelines, BMI over 30 is considered obese, under 18, extremely underweight, and between 18 and 25, normal.

Body Fat Percentile

Body fat percentile provides the most accurate estimate of body composition. Body fat percentile is an indication of the percent of your body that is made of fat. Normal body fat percent for women is 20 to 30 (for men it is lower). In women, below 17 is extreme low body fat; between 30 to 33, high body fat; and above 34, extremely high body fat or obese. The recommended healthy body fat percentiles increase slightly with age.

Body Fat Standards for Women Recommended by Age Group
 

Body fat percentile measurement methods vary in practicality, cost and accuracy. The most accurate measurement is through DEXA, an expensive measurement done in a radiology lab or doctor's office; this is the same radiographic measurement used to determine bone density. The second most accurate method is water displacement, although this requires your body to be underwater in a special tank, even more impractical and expensive. One of the simplest, most common measures of body fat percentile measurement is skinfold measurements, in which a tester uses calipers to measure fat pinches at various sites on the body. This evaluation is very dependent on the tester's skills; if done by an experienced tester, it can be up to 3 percent accurate. The other common method is bioelectric impedence; this is a machine that looks like a scale and is common in many gyms and even available for home use. This can be a very unreliable measure, as it is highly dependent on water weight, temperature, electrolytes, blood flow, and other factors. Bioelectric impedence is even less accurate in athletes with a large amount of muscle.

All these measurements are interesting and can suggest health, but should not be the basis of an exercise or nutrition regime. Remember, if you are using weight as your guide, that muscle weighs more than fat. If you are increasing strength but not changing your weight, you are becoming leaner. The following are loose guidelines for healthy weights in athletic women. The lower numbers are for petite, small-boned, less-muscled frames; the higher numbers accommodate for large bones and bigger muscle size.

Healthy Weight Guidelines for Muscular, Athletic Women (BMI 18 to 25)