For a very accurate determination of your body fat percentage, visit a facility that has a dual-energy x-ray absorptiometry (DEXA) scanner. A DEXA scan involves x-ray technology that's used to estimate muscle tissue, bone mineral density and fat tissue in all regions of the body with a high degree of accuracy. It uses a combination of two x-rays to calculate body composition in various body segments, so you can see which part of your body holds the highest percentage of fat (or muscle). The scan imparts about as much radiation to your body as the TSA body imaging devices at airports, which is not very much. A DEXA scan is considered the gold standard of determining fat percentage in your body as a whole, as well as regional parts such as arms and legs.  Unlike MRI or CT scans, a DEXA scan doesn't involve lying inside a claustrophobic tunnel or enclosure. Instead, you lie on your back on an open table and an X-ray scanner passes slowly over your body — the procedure usually takes about five minutes, although it depends what part of your body is being scanned. Most major universities (exercise physiology labs) and many healthcare facilities have DEXA scanners. Ask your doctor for a referral to one in your area. They were originally developed to measure bone mineral density. The cost ranges from $100-200 USD out of pocket if your health insurance plan doesn't cover it. Since muscle tissue and bone is much denser than fat tissue, determining body density is helpful for understanding body composition. With underwater weighing, you are submerged in a water tank and the amount of water that's displaced is measured, which is used to calculate tissue density and full-body composition of fat. The more water you displace, the more bone and muscle tissue you're assumed to have, so the lower your fat percentage. Underwater (or hydrostatic) weighing is a very accurate measure of body fat percentage — its error is only 1.5% if the test is performed according to guidelines.  The main downside to this method of measuring fat percentage is that you have to get wet and be submerged underwater for a few seconds once you completely exhale your breath. Athletes often have denser bone and muscle tissue than non-athletes, so their measurements can underestimate body fat percentage using this method. Ask your doctor or do an internet search about which medical or research facilities in your area do hydrostatic weighing — there may not be many. You may have to travel out of your area. The cost should be comparable to getting a DEXA scan. This method of measuring body fat is based on the principles of light absorption, reflectance, and near-infrared spectroscopy. To estimate body fat composition, a computerized spectrophotometer with a hand-held fiber optic probe is used. The probe is pushed against a body part (often the biceps muscle) and emits an infrared light, which passes through fat and muscle tissue towards bone and is then reflected back to the probe. Density measurements are obtained and incorporated into predictive equations (also taking into account your height, weight, and body type) to give an estimate for overall body fat percentage. This method is not as accurate as DEXA scanning or hydrostatic weighing, but it's likely a more accurate assessment of body fat percentage than you can get at home with calipers or bioelectrical impedance scales.  NRI tends to be less accurate with people who are either extremely lean (<8% body fat) or obese (>30% body fat). The amount of pressure applied to the fiber optic probe, skin color and hydration levels may cause results to differ and be inaccurate. NRI devices are widely available at many gyms, health clubs and weight-loss centers for a minimal fee, or sometimes free. Your doctor's or physiotherapist's office may also have an NRI device.
قم بإجراء مسح (DEXA مقياس امتصاص الأشعة السينية ثنائي البواعث). قس وزنك تحت الماء. احصل على قراءة NRI (تفاعل الأشعة القريبة من تحت الحمراء).