Body-fat percentage, even more than weight, is an important indicator of overall health and fitness. There are several ways to measure body fat, including caliper measurements and hydrostatic testing (considered the gold standard). Over the past decade, numerous products have been introduced to measure body fat at home, most utilizing a technology called bioelectrical impedance. (Tanita was one of the first to introduce this technology for home use.) These devices calculate body fat by a formula that takes into account age, gender, body weight and the amount of electric resistance encountered between the electrodes, which are usually pressed against the feet or hands. While most manufacturers claim their products are highly accurate, there is generally a 2-4% margin of error.
The Tanita BF-680W Scale plus Body Fat Monitor with Body Water Percentage looks much like a standard digital scale and features a large display with easy-to-read numbers. The scale stores data for two users (a guest mode is also included); each user inputs relevant data including height, age, sex and fitness level (athlete or normal). The enclosed instruction manual offers guidelines for determining fitness level based on the time and intensity of weekly workouts. Once the information has been inputted, the user steps on the scale, aligning the feet with the surface electrodes. An undetectable current passes through the foot and up the leg and circles back down the other side—the amount of resistance the current encounters is recorded and used to calculate body fat. Weight is displayed immediately while body fat percentage is displayed a few seconds later, followed by body water percentage.
In our comparisons to measurements taken with calipers, the Tanita Scale was accurate within 1-2%. As with any bioelectrical impedance device, it is important to be adequately (but not overly) hydrated and to measure body fat at the same time and under the same conditions every day. When used on a consistent basis, the Tanita Scale enables users to track both weight and body-fat percentage. However, it is important to note that body-fat changes occur very slowly and, unlike weight changes, may not show up for some time.
What we liked:
- Easy-to-use device for measuring weight, body-fat percentage and body-water percentage
- Large display was easy to read
- Body-water percentage measurements increase reliability of results
- Provides relatively accurate results when used under recommended conditions
What we didn’t like:
- Lack of changes in body-fat percentage may be discouraging to some dieters/exercisers.
January 11, 2010