This model of the Tanita provides the following data: weight, body fat %, body water %, muscle mass/physique rating, bone mass, visceral fat, daily caloric intake/metabolic age. The Tanita uses Bioelectrical Impedance Analysis to calculate your body composition. It passes a low electrical signal through your body, carried by water and fluids. According to their literature, "Fat tissue does not contain much water and creates resistance to impedance to the signal. (Fat is approximately 10-15% hydrated, whereas muscle is normally between 50-70%.)" The Tanita uses this information along with formulas based on other information that the user provides: height, weight, gender, body type and age, to estimate the user's lean and fat tissue. I've discovered that my hydration level is the most important factor in getting consistent data. But, more about that later.
The Tanita was very easy to set up. There is a guest mode, and up to four users can store their personal data to get more accurate readings. Once I turned the scale on (it runs on 4-AA batteries), and selected my Personal Key Number, I entered age, sex, height, and activity level (I selected "3", which is an "adult involved in intense physical activity of approximately 10 hours per week and who has a resting heart rate of approximately 60 beats per minute or less." ) That's it, set-up complete.
Each time you weigh yourself, you need to first select your personal key before stepping on the scale. Tanita recommends that you weigh yourself under consistent conditions of hydration. This is important, because you can get very different numbers with seemingly insignificant differences in hydration. You also need to be barefoot, so that your skin can make contact with the electrodes. Further, it is recommended that you be unclothed, and wait three hours after rising, eating or exercising. These stipulations basically give me a small window of time on weekdays, so I find I'm not using the scale every day. But, if I use that window, I have the best chance of getting consistent readings, and I can see the effect that illness or poor hydration has on my readings. When I am adequately hydrated, I see my highest muscle mass, highest bone mass, and lowest fat percentage. Not surprisingly, this corresponds with my highest weight, though not always. Also, some of my lowest body weight readings were coupled with some of my highest body fat percentages, simply because I was dehydrated. For me, my best readings happen when I weigh myself after work and before my workout, and when I've had two meals (breakfast and lunch), two snacks, and about 60 oz of fluid, at the time of weighing. Here are the differences I've seen between my highest and lowest readings: weight-4.2 lbs, muscle mass-9 lbs, bone mass-0.4 lbs, body water-5.3%, body fat-7.3%. My worst readings were when I had an intestinal bug, my best were two weeks after I finished the Challenge Phase of the Spinervals Super 6 training plan. It was an intense month of focused muscular endurance training.
Time for some conclusions: The day I recovered from two days of intestinal nastiness, I gained 2 lbs, gained 0.4 lbs of bone mass, gained 9 lbs of muscle mass, lost 6.6% of my body fat, and had 4.8% more body water. Clearly, I didn't have 9 more lbs of muscle from one day to the next, but it illustrates how important hydration is for correct readings. I can see trends, and I can use those numbers to make decisions about my training. For example, when I look at my numbers for January 14th and February 11th, all of my numbers are virtually the same, except I weighed 1.6 lbs less and had 1.2 lbs less of muscle mass on February 11th. Since my current training phase has been mostly aerobic endurance work, I feel I've done a good job maintaining my muscle gains, and I'm ready for the next phase of my training. I also really like the Tanita because it forces me to focus on hydration, something I have been casual about in the past to my detriment. So, if you like to quantify your progress and are serious about training and improving your chances for success, the Tanita scale can be a very useful tool to have.
