Body fat analyer scales surely wrong?

your assuming that as you have a normal BMI you will have low body fat, this is the problem you can be fairly low in weight but have little muscle

my BMI is 28 but my scales tell me my body fat is 38.6, this was over forty before I started excercising.

If you start working out your weight might change very little (muscle weighs more than fat) but you will see your body fat percentage change

I agree, whilst you maybe not be overweight if you don't don't any exercise your fat percentage is going to be much more than your muscle. Since I started working out 2 months ago my fat has decreased by 2.7% and my muscle has increased by 1.8%

I might be wrong here but doesn't chest class as fat? I'm fairly large busted so blame some of my fat % on that hehe

Electronic scales will only measure the fat percentage of the lower part of your body, and can be fairly inaccurate. Body fat calipers are about the best home method of body fat% testing, but can be inaccurate until you get used to them and ensure you measure in the same spot and with the same method every time.

However, BMI is no indication of having a healthy level of body fat - completely ripped bodybuilders can have a BMI that classes them as obese, even though they have single digit fat percentages - the term that they use in bodybuilding circles for having a healthy BMI but an unhealthy body fat % is being "skinny fat".

At the end of the day, I wouldn't worry too much about whether the percentage is accurate or not - the important thing to worry about is whether you see a downward trend over time.

Those electric scales are horrible, the readout they give you is based on BMI and activity level. If you change your activity level the BF% will change, best bet is to use callipers and the mirror.

I like a body fat monitor, but you have to take into consideration the differences in BF monitors to realize that none of the ways of determining body composition are 100% accurate or comparable to each other. So, whatever method you pick, stick with it to compare results to be able to monitor changes over time. So, in order of accuracy (most accurate to least accurate), here are some bits of info on the various body composition analysis methods.

DEXA Scan: This is like getting an x-ray or CT scan of the whole body. It literally looks at the inside of the body to see what is fat and what is bone, muscles, etc. The drawback to this method is that it assumes that each part of the body is symmetrical all the way around and that isn't necessarily true. For example, some people have larger quadriceps muscles on the front of the legs and more fat around the hamstrings on the back of the leg, or more fat in the stomach then in the low back. Another drawback is that it does use x-rays to determine body fat, and excessive exposure to them can be harmful. Plus, depending on where you live they may or may not be accessible or affordable.

Hydrostatic Weighing: This is a measurement of what you weigh underwater by measuring water displacement based on the fact that fat has less density then water and muscle, bones, etc. have a higher density so you are essentially only weighing the muscle, bones, etc. in the body. It has been the gold standard of body composition testing for years, but has recently been surpassed by DEXA scanning. The drawbacks are that you have to wear very little clothing while in a lab setting, plus you have to exhale all the air possible and hold your breath while under water to get an accurate reading. Generally, it is only accessible in a lab setting so it can be financially inaccessible.

Bod Pod: This is a measure similar to hydrostatic weighing only it uses the weight of the body and the air displacement of the body to determine body composition. The drawbacks to this are similar to the hydrostatic weighing. This is also hard to get to in some areas, although some large cities now have more accessible versions.

Bio-Electrical Impedance: This is the technology used by the body fat scales and the handheld devices. It basically uses an electrical current running through the body to estimate body fat because fat is not as conductive as muscle, bones, water, etc. in the body. There are several different versions of bio impedance though. The most accurate is the version in some gyms that uses an electrode at the hand and another at the foot so that the current goes through the full length of the body. The scale version would be the next most accurate because it measures from foot to foot so that the current flows through the midsection and lower limbs, which is where most people store most of their fat. That being said, it can give a higher reading then the actual body fat % because it assumes that the whole body is just as fat as the area where the current flows. The least accurate is the handheld device because the electrical current flows from hand to hand and through the shoulder region of the body. The reason it is the least accurate is that most people don't carry as much body fat in this area then they do lower in the body, so it will give a lower body fat reading then is actually in the whole body. Because of the differences in the way they determine body composition, there are different charts for what an acceptable body fat is based on the piece of equipment used, so if you choose one of these methods be sure to go by the chart in the book that comes with it. The drawbacks of this method are that hydration level can effect the reading quite a bit. So, if you use this measurement, make sure you are drinking plenty of water, haven't worked out in 12 hours, and don't compare measurements at different times in the menstrual cycle.

Calipers: Calipers determine body fat based on pinching skinfolds at various places on the body. If you use a formula that uses more skinfold sites on the body it is more accurate then the 1 or 3 site formulas, but they still only measure body fat at the skin level. The drawbacks are that they can't "see" the body fat around the organs (which is the most dangerous body fat) so their accuracy is a lot lower then the other methods. Also, there is a lot of variability in the skill level of the people using the calipers. They can artificially decrease body fat readings by pinching too hard or artificially increase body fat readings by pinching muscle in with the fat. Although they are available at any local supplement shop or online for anyone to use, they should only be trusted when used by someone who is specially trained in using them and can only be compared to their previous measurements if done by the same person due to variability in how each person does the measurements.

Measurements / Measurement Formulas: These are the least accurate for determining body fat because they can't tell if they are measuring muscle or fat, but they are great for seeing losses not shown on the scale. The formulas used to turn measurements into body fat % vary in accuracy so if you choose this method, be sure to stick with the same formula. This is probably the least expensive way of estimating body composition, but is also the least accurate, so you have to weigh your options.

You are absolutely right. Just because you weigh less does not mean you have lean muscle. If you've lost weight it is very possible to have lost lean muscle and not fat. You need to add strength training to your exercise regimen. I do crossfit and I know that I have lost only body fat as I watch both very carefully