Are You Losing Fat, or Just Losing Weight?
The Importance of Body Fat Percentage
Did you know… That two people can have the same height and weight, but very different percentages of body fat?
Did you know… That as we age, we tend to gain fat around our organs (“visceral fat”) that can’t be detected by measuring “skin folds” or even with a scale?
Did you know… That chances are that if you are losing weight, you will lose muscle as well as fat?
Weight management is a goal on a lot of people’s minds. People get on the scales in the morning, and the number they see may determine how they feel about themselves. But the truth is that some people make think they are overweight, when the amount of fat they have on their bodies is just fine, while others may carry hidden fat that the scale won’t tell them about.
What is Body Fat Percentage?
Our bodies are made up of a lot of different kinds of tissues (plus a lot of water). There is muscle, fat, bone, and specialized tissue such as is in our various organs. The body fat percentage is just that –- the percentage of our weight which is made up of fat. Body fat percentage is similar to terms such as body fat ratio and body composition. The part that isn’t fat is called our “lean body mass.” A 160-pound person with a lean body mass of 120 lbs has 25 percent body fat (40 lbs of fat). That may sound like a lot, but our bodies need a certain amount of fat for insulation, energy storage, hormone production, and other functions scientists are just discovering.
How Much Body Fat Should a Person Have?
This depends upon a few variables. Women need more body fat than men. Breasts are almost all fat, and women have more fat around their hips -– that’s just the way it was meant to be. If a woman’s body fat drops too low, she will stop menstruating. Also, men naturally have a greater amount of muscle bulk. Another factor is age. As people get older, their muscles tend to shrink, and they tend to accumulate visceral fat. This is at least partially related to the decline in testosterone and other hormones. It is important not to confuse BMI with body fat. The BMI (body mass index) numbers are NOT percentages of body fat. I often see advice on Web sites where the two are plainly being confused. For example, a BMI of 29 is in the overweight range for women. This has nothing to do with 29 percent body fat, which is considered healthy.
What’s the Difference between Body Fat Percentage and BMI?
BMI (body mass index) is a formula based on height and weight. It was developed because in the general population, it is correlated with body fat. However, there are quite a few groups of people for whom BMI is not as accurate –- short women and muscular people, to name two. BMI also varies according to some ethnic groups. Also, for people who are interested in changing their body composition and not just their weight, knowing body fat percentage is an improvement over BMI. For example, if you are exercising to build muscle (a good goal), knowing your body fat percentage is a good idea. Also, when losing weight, you want to preserve as much lean body mass as possible. (Low-carb diets generally produce better results than high carb ones for this purpose.)
How can I determine my body fat percentage?
There are several ways to find out your body fat percentage. Unfortunately, the more accurate the method, the more of a hassle and/or expensive it tends to be. This is a short capsule summary. Exercise Guide Paige Waehner has more detail, and here is even more in-depth information.
DEXA scan – full body X-ray scan of the same type used for bone density. Very accurate.
Hydrostatic Weighing – Weighing under water (completely submerged, with all air blown out of lungs) – Very accurate when done professionally.
Skin-fold calipers (“pinch test”) – Simple, but needs to be done by someone who is trained, and you can’t do it on yourself. Wide variations in accuracy for people without training. This is the method that CORE Rhythm Fitness uses...
Bioelectrical Impedance (BIA) – These are scales and hand-held devises that run low-level (and painless) electrical current through you. They can be accurate, although the accuracy varies according to the specific device (do your research) and how it is used. Best results are obtained first thing in the morning with no alcohol consumed for 2 days prior, and no exercise the night before.
Navy tape measure method - This is a formula based on several body measurements taken with a tape measure. It can be quite accurate (it is used by the military), but it does depend upon your ability to accurately measure. Using centimeters rather than inches is the best, but using inches within ¼ of an inch works. To be sure, measure yourself 3 times and take the average. I have a calculator using this method. It is especially useful for tracking yourself over time.