I received my new Tanita BF680W bathroom weight scale that measures body water and body fat (as well as total body weight) for Christmas. However, I was so caught up in other activities and responsibilities that I didn’t start using the scale till this past week. I am finding the way it works and the information I receive to be fascinating. Because body water influences the body fat reading it inspired me to take a closer look at what is considered to be normal body water percentages and how a person knows whether or not he or she is well hydrated.
As I mentioned in my previous articles (Body Fat Scales and Body Fat Monitors)what seems to be most important for the body fat measurement with BIA (bioelectric impedance) on a body weight scale is consistency. Because affordable home/bathroom weight scales are not as precise as those used in research settings the accuracy is not likely to be as good. But if the trend with weight loss or gain is a steady change in either direction, then the information is consistent and a good way to assess body fat loss (or gain).
My additional research has now provided me with a little more information to share. It seems that the accuracy of the body fat measurements with BIA will be closer to actual body fat for those who are within a normal body fat range. However, BIA tends to be significantly off for those who are lean (less than 25% body fat in women) and those who are significantly overweight (more than 33% body fat in women). (American Journal of Clinical Nutrition, 2005) This underscores the need to check consistency in reported results and to not take the actual measurement too seriously. (Body fat tends to come off quite slowly unless you are exercising very heavily as occurs in reality T.V. shows such as The Biggest Loser. The participants are actually losing a great deal of water weight along with fat loss to achieve such high loses each week.)
Having said that, total body water does seem to influence the reading for body fat measurement for me as the product instructions relate. I’ve been playing with how it works and I will have better results to report to you over time. But I do have some interesting observations with respect to the question of what is normal for body water percentages and how we know when we are getting enough water in our diet.
If I weigh myself first thing in the morning after using the bathroom, my body water percentage is lowest and this is reflected in my total body weight and the reported body fat. This makes sense because we lose body water when we sleep from evaporation and possibly sweating if it is too warm or you happen to be old enough to experience hot flashes like me! (Take note that I said “old enough” and not old! Who me old? Nah!)
Image via WikipediaMost of my measurements in this short week or so have actually been somewhat later in the morning after I have eaten breakfast and rehydrated. (I do need to establish a set time for the most consistent results.) What caught my attention is that the reading for my body water is typically in the 48 to 50 percent range. That seemed low but it now makes sense based on what I have learned.
About 50 to 80 percent of our body weight is made up of water. However, the brain, muscles, and blood have significantly more water than the rest of the body. The average person is about 50 percent water by weight otherwise. Total body water for the average reference woman is about 60 percent. (American Journal Phys. Endocrin. Metab., 2003)
If I measure my body water percent by bending over double to put my hands on my feet (Do be forewarned this is not for everyone! I am lucky to be flexible), I get a reading of about 60 percent body water! I guess what happens is that the small electric current goes through more of my body in that awkward position then when I am measured standing up (When standing the current travels up one leg, across the hips, and then down the other leg). Evidently I am close to the average for water weight.
[Note: When a person gains a substantial amount of weight, the percentage of body fat increases and body water decreases. It seems that those who are extremely overweight/obese may have a body water percentage as low as 37 percent with a body fat percentage as high as 57 percent. (American Journal Phys. Endocrin. Metab., 2003)]
So how can we know we are getting enough water? And how much of that water do we need as plain water? The standard recommendation to drink 6-8 glasses of water or more each day may or may not hold true for you.
We get water from the food we eat and beverages we drink as well as plain water. If you have read that caffeine can act as a diuretic and be dehydrating you will be pleased to know that this has been disproved. Recent research has shown that caffeinated beverages can be as good a source of water as plain water. And whereas we may need as much as 11+ cups of water a day from all sources, the easiest way to meet your needs is to pay attention to your thirst. This works remarkably well for most people with an exception for some such as the elderly. The other way to keep tabs on whether or not you are getting enough water is to make a quick assessment of your urine. If is it is light colored or clear chances are very good you are getting enough water.
There are circumstances in which you might retain excess water. Warm temperatures, certain medications, eating salty foods, and hormone fluctuations with menstruation can cause water retention. Certain medical conditions can also cause water retention. But these situations go beyond the scope of what I am covering here and would make a good article for another day.
If you would like to learn more about basic water needs and how they are assessed you may want to read an article I just posted at my website Chocolate Veggies: Water Wisdom! Also, do choose your beverages carefully. My article The Beverages You Drink Could Be Making You Fat goes into this potential problem.
I’m happy with my Tanita BF680W bathroom scale so far. (Body Fat Monitor and Weight Scale Reviews) I can see how it will keep me motivated to track my weight loss/maintenance efforts. I did manage to put on a couple of pounds over the holidays along with just about everyone else. So this body weight scale will be just what I need to have a much better sense of whether or not I am making progress with fat loss.
How about you and your weight loss or maintenance efforts? Let me know what additional information you might need to be successful!
Till next time, watch those calories and eat healthy food!
[Update Fall 2011. I've had my Tanita scale for over 2 years now. During that time I seem to have brought my body fat below 25%. As such I am finding it harder to even track trends in fat loss. The body fat measurements seem to jump around with no rhyme or reason.
I've been very happy with this scale until now and believe whatever the latest version of this scale might be it will likely work well for you unless your body fat is below 25%.]