How to Measure Subcutaneous Body Fat?
Do you know what is your body fat percentage? Do you know how many subcutaneous body fat you carry on your body? Before you begin a serious weight training regimen (or cardio training), record your body weight and body fat percentage. Knowing your body fat percentage can help you track your progress toward your fitness goals. However, finding your body fat percentage is not as simple as stepping on a scale.
Importance of knowing your body fat percentage
There’s a lot you can learn from knowing your body fat percentage. In fact, it’s one of the best ways to monitor a person’s health at any age. Carrying too much fat makes people prime candidates for fat triggered conditions such as heart disease, high cholesterol, high blood pressure, diabetes mellitus, digestive diseases and even some forms of cancer.
Monitoring body fat should be a regular routine for anyone who is dieting or trying to reach goals in fitness programs. For example, if you are a bodybuilder, you may weigh heavy on the scales and have quite a high BMI, but have a body-fat percentage much lower than average. That is when knowing your body-fat percentage would reassure you that you’re on the right path.
Knowing your body fat percentage also allows you to calculate your lean body mass, which is essentially all parts of your body that aren’t fat. Knowing your lean body mass will help you calculate precisely how much protein you should be eating on a daily basics, another crucial metric that will help you enormously in your quest for optimal health.
Once you determine your body fat percentage, subtract it from 100 to determine your percentage of lean body tissue. From there, multiply that percentage by your current weight to get your total amount of lean body mass. For example, let’s say that you use one or more of the methods we list below to learn that you have 30 percent body fat. That means you have 70 percent lean body tissue. Then you take 70 percent of your total body weight (multiply it by 0.7) to get your lean body mass.
There are several ways of measuring body fat percentage. Each has its pluses and minuses. We’ve listed them below in order of cost, complexity, and accuracy, from lowest to highest.
Methods to Measure Body Fat Percentage (Body Composition)
Clearly, height and weight measurements are not very accurate for assessing your body composition. To give you a more accurate idea of how much fat and how much muscle you have, there are a number of techniques for measuring body composition. These will tell you how much of your weight is muscle or fat as a percentage of your total weight. The only method that is 100% accurate is cadaver analysis. Clearly this is impractical so we have to use other methods.
I. Photo approximation
Photo approximation is the least accurate method for determining body fat percentage. The main idea is to take a photo of yourself in your underwear and then compare it to photos of people at different body fat percentages. You can find the photos for comparison on Cronometer.com or by doing an Internet search for “body fat percentage” and selecting the Images tab on the results page. Always try to be objective about your appearance. In that case even this method can give you a general idea of where you are and what the next stage in personal health actually looks like. This is the cheapest variant to quantify your body fat percentage. You can also use the following visual body fat chart:
II. Skinfold calipers
The skinfold technique measures fat just under your skin at various places on the body. You can pick as many as ten sites to measure the thickness of subcutaneous adipose tissue. The combined measurement of the abdomen, triceps, chest, and thigh skinfolds is usually enough for an accurate reading. For that purpose we use calipers. Caliper is a device that pinches up folds of fat away from the underlying muscle tissue. The measurements are plugged into a formula that calculates body fat and lean mass percentages.
The accuracy of the skinfold technique depends on the skill of the person performing the measurements and the number of sites measured. For best results, it’s advisable to have your skinfolds measured by a skilled technician, perhaps someone at a local gym or a nurse at your doctor’s office. Use the same person each time too. And note that the skinfold technique does not work well with very obese people. Most calipers are usually not large enough to measure their skinfold thicknesses.
III. Bioelectrical impedance analysis (BIA)
Most body fat monitors and scales work using bioelectrical impedance analysis (BIA). In other words, this method uses a portable instrument to conduct an electrical current through the body to estimate fat. Therefore, a mild electrical current is sent through the body between electrodes attached to two specific points of the body (either between the hand and opposite foot, or from one foot to the other). The principle is that lean tissue (such as muscle and blood) contains high levels of water and electrolytes and is therefore a good conductor of electricity, whereas fat creates a resistance. Increasing levels of fat mass result in a higher impedance value and correspond to higher levels of body fat.
The monitor analyzes the readings from this signal with stored personal data (e.g., height, weight, gender, activity level). This information is converted to a body fat percentage in seconds.
The advantages are the machine is portable, simple to operate and testing takes less than one minute. These devices can come in a scale version or a handheld version, but they both utilize the same technology. Because of the small size and low cost of the handheld version, bioelectrical impedance is widely used by fitness facilities and by individual consumers.
The disadvantage is the poor degree of accuracy compared with other methods. For example, changes in body fluid levels and skin temperature will affect the passage of the current and therefore the body fat reading. It tends to overestimate the body fat percentage of lean muscular people by 2-5% and underestimate the body fat percentage of overweight people by the same amount. It is important that you are well-hydrated when having a BIA measurement. If you are dehydrated the current will not be conducted through your lean mass so well, giving you a higher body fat percentage reading.
There are several strict protocols that you need to follow before testing with BIA. The protocols are:
- No eating or drinking within 4 hours of the test.
- No exercise within 12 hours of the test.
- Urinate completely within 30 minutes of the test.
- No alcohol consumption in the previous 48 hours before the test.
IV. Underwater weighing
The gold standard of body composition measurement is underwater weighing. This technique, although highly reliable, is often performed only in university lab settings and hospitals, so access is often a problem. Most personal trainers are able to measure a client’s body fat using either skinfold calipers or a BIA device free of charge or for a nominal fee.
Underwater weighing works on the Archimedes’ principle which states that when an object is submerged under water it creates a buoyant counter force that is equal to the weight of water that it has displaced. Since bone and muscle are more dense than water, a person with a higher percentage of lean mass will weigh more in water, indicating a lower percentage of fat. Since fat is less dense than water, a person with a high fat percentage will weigh less in water than on land.
In this test, the person sits on a swing-seat and is then submerged into a water tank. After expelling as much air as possible from the lungs, the person’s weight is recorded. This figure is then compared with the person’s weight on dry land, using standard equations on a computer, and the fat percentage calculated.
Underwater weighing often is impractical because it requires a special water tank and other nonportable, expensive equipment. The subject must exhale completely, submerge without taking a breath, and remain motionless until the water is still and the scale is steady—clearly not a welcome experience for everyone!
V. Skulpt Aim (electrical impedance myography, or EIM)
This technology uses impedance principles like bioelectric impedance, but unlike BIA, the alternating current only passes through the muscle group that you are attempting to measure and not through your entire body. This means that this device can provide you a body fat measurement for specific muscle groups, a feature that BIA and other body composition methods can’t offer. The EIM device shown in this post also offers a new measurement called muscle quality or MQ. Muscle quality measures the leanest of the muscle group being measured. Because EIM uses a localized current, EIM is not susceptible to the same issues which cause errors and inaccurate readings in BIA. An EIM consumer device costs approximately between $150 to $200.
VI. Bod Pod (air displacement plethysmography)
Better known as the Bod pod, this 2 component method is based on the same Archimedes principle as underwater weighing. The testing process requires you to wear compression shorts and no shirt. If you have hair you must wear a tight fitting cap, like a swim cap. Women have to wear a Spandex like swimsuit or single layer compression shorts. The reason that you have to wear tight fitting clothes is because air can get trapped in various places throughout the body and can alter the testing results. During testing you have to sit in an egg shaped like container. A computer is linked to the testing chambers and spits out your results. This method is not suggested for kids or infants. The cost associated with this testing method runs around $45-$60 per session. Some facilities that own Bod pods, often sell packages which reduces the per session cost.
VII. DEXA scan (dual-energy X-ray absorptiometry)
DEXA is a highly accurate way to assess body fat. However, it’s expensive and is generally limited to clinical research studies. This method was originally developed to evaluate bone mineral density with a scanner that measures body composition using low energy X rays. As two X ray beams pass through the individual, the amount of X ray absorbed by the tissue reveals differences in fat from lean mass. The tissues with greater density (bone and muscle) show a greater reduction in X ray that is allowed to pass through them. The level of radiation is low enough that DEXA is approved by the FDA as a screening device to predict body composition. It would take approximately 800 full body DEXA scans to equal the amount of exposure to radiation received from one standard chest X ray.
How accurate are these methods?
Presently, there is no one simple method of measuring body fat that is extremely precise. The best that can be expected is an estimate of fat content. Methodologies that rely on height/weight tables provide a rough estimate of ideal weight. However, these methods do not account for individuals with above-average muscle mass. Underwater weighing presently provides the best estimate of body fat, with about a 3% error. Because this method is costly, time-consuming and expensive, fitness instructors have looked to other simpler methodologies. Presently, skinfolds provide a fairly good estimate of body fat. The procedures are easy to learn, and the monetary and time costs are low.
Closing thoughts about measuring body fat percentage
Measuring body fat percentage is slightly more complicated, but it is what will help you determine how much of you is lean body mass and, therefore, how much fat weight you can “afford” to lose.
Most personal trainers are able to measure a client’s body fat using either skinfold calipers or a BIA device free of charge or for a nominal fee. With these two methods you can easily measure your body far at home.
