Health and Fitness Information Center

Tanita Body Fat Frequently Asked Questions, Part 4E

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However, factors such as temperature, how much exercise you have done, when you last had a drink, medical conditions (including menstruation), medications, alcohol, caffeine etc., can also affect the hydration level of a person's muscle tissue, which can then affect the body fat reading.

The time of day can also affect hydration levels, as well as fluid distribution in the body. It is for this reason that Tanita recommends that readings are most consistent when taken between 5 and 7 pm before the evening meal. If your body fat % is not within the healthy range it will impossible to obtain the 50-55% hydration levels.

12. I get different weight readings from other scales, is my body fat monitor out of calibration?
Tanita have a very low rate of returns of faulty products - less than 1%. Often it turns out that when tested with calibrated weights it is the Tanita scale that is correct and the others that are faulty!

The only way to be sure is to test the scale with a calibrated weight. If, exceptionally, the scale is incorrect it is fully guaranteed for 3 years PROVIDED YOU KEEP YOUR PROOF OF PURCHASE.

13. Why do I get different Body Fat % readings in the same day?
The weight of fat in a person's body is unlikely to change by a large amount during the course of a day: In the same way that the bones and internal organs do not change. However, the weight of a person's body is constantly changing as food and water is taken in and passed out. In addition, a person's hydration status is changing constantly - this is water contained not in the stomach, but in the muscle tissue where it is needed for the body to function. So why does the body fat % change? It is important to remember that the reading shows the PERCENTAGE of your total weight that is fat, not the actual WEIGHT of fat. So, mathematically, if your total weight goes up because you have more water in your body, the percentage of your weight that is fat will be lower even though the actual weight of fat has not changed.

Conversely, if you are dehydrated, your total weight will be lower giving a higher % of fat. This is easier to see with scales that show total body water because as the water % increases the fat % decreases and vice versa. Please bear in mind that the body fat monitor calculates the water, muscle, and bone as the first part of the equation, and then subtracts this from the total weight - the rest being fat. If you "cheat" the scales by standing on them with a pile of books it will give a (incorrect) higher fat reading. In the same way having a very full stomach, or anything that increases the weight abnormally will give an incorrect reading. The answer is - don't cheat if you want accurate results!