Any thoughts on how accurate the scales that claim to measure body fat are? They also claim to measure percentage of water in the body. I guess I am just unsure of how a scale you stand on would know be able to accurately measure these things. Thanks in advance for any info.

I have this scale by Tanita that does body fat and body water. If you look on the Tanita webpage I think it explains how it figures it out. It is not as accurate as they can do at the gym. It is consistent, though. I have seen a steady drop in my percentage as my weight goes down. It doesn't vary wildly or anything so you can tell you are making progress even if the number isn't exact. The body water percentage actually uses a formula so it is not technically checking the water in your body each time. I take water pills for high blood pressure. If I don't take my pill I can watch my water % go up. It is not really helpful to me at all. I do love the scale.

Thank you so much for the info and the link. It seems like to me that when you lose weight the scale automatically drops body fat %. However, if for instance you stayed the same weight but lost fat and gained the same amount of muscle I'm not sure if it could REALLY tell.

I have a body fat analyzer scale, and the way the instructions explained that it measure body fat is by sending a small electrical current through the body. I guess it goes up one foot and comes out the other or something. Anyway, it measures the amount of time it takes for the current to pass throught the body. Evidently, the current passes more quickly through muscle than it does fat so that if your weight stays constant, but you gain muscle while losing fat the current should pass more quickly through your body and the scale should register a difference in body fat percentage. Hope that was helpful and coherent.
Christine

I just got a Tanita BC533 Innerscan scale, and love it... so here is my take on the mind behind the machine

When you lose weight, the scale does not drop your body fat % automatically. It is possible to look "thin" but really have a unhealthy body fat level, and for that matter, a person can look big and have a lot of muscle.

The thing with the BIA scales that use the electric current is that they are very affected by your hydration level. If you are dehydrated, then the scale "reads" you as having less muscle/more fat. So, say you wake up in the morning, go to the bathroom and run to your scale to see how you are doing... after a long night of rest (and no water), you will be dehydrated. For me, a long-time morning weigher, this is a new realization. Of course, I used to like the fact that I weighed the least in the morning BECAUSE I was dehydrated

The best time to weigh in/get scanned is 3 hours after any of these:
- Waking up
- Showering/swimming
- A hard workout
- Eating
- Drinking alcohol

You should also make sure you are getting in at least 6 cups of water a day, for health reasons and to make the fat readout closer to reality Even with these caveats, the BIA scales can be off +/- 5%. It's not a perfect science but it's a great motivator and it DOES give you a close number.

Another blurb for women: because of our monthly cycles, our bodies are all over the place for water content weekly, so it is suggested that for the 1st month you have such a scale, to scan daily to get a "baseline" average that takes into account PMS bloating and loss... then with that in hand, to scan body fat levels only 2x/month because muscle/fat changes are a sloooow process and scanning more than that is not going to give you any real valid numbers.