Bioelectric impedance (BIA) is a non-invasive method to determine body composition. It is based on the resistance of a fat-free mass to administration of a high frequency, alternating, low amplitude
(50 kHz) electrical current. It is inexpensive, easy to perform and reproducible . Bioelectrical impedance has been validated against both underwater weighing and isotope dilution, two bench research gold standards used for determining body composition . One drawback of BIA is its assumption of a normal body water status being approximately 72%-74%. Therefore, in clinical cases of body edema or body dehydration, BIA may be inaccurate . A study in patients with renal failure found BIA to be inaccurate secondary to an abnormal volume status . In contrast, BIA was found to be accurate in determining muscle mass in a group of patients with cystic fibrosis when compared to isotope dilution methods .
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WHAT IT IS A three-phase plan that has been likened to the low-carbohydrate Atkins program because during the first two weeks, South Beach eliminates most carbs, including bread, pasta, potatoes, fruit and most dairy products. In PHASE 2, healthy carbs, including most fruits, whole grains and dairy products are gradually reintroduced, but processed carbs such as bagels, cookies, cornflakes, regular pasta and rice cakes remain on the list of foods to avoid or eat rarely.