BMI v's Body fat %

okgirl

Hi there,

can anyone tell me the difference between BMI and Body fat % ? How are they worked out etc?

ali.c

BMI is pretty much a ratio of height to body weight whereas body fat % is an estimation of how much of your bodyweigt is composed of fat. BMI can give inaccurate results though esp if you have alot of muscle mass, so a person who has little fat but alot of muscle can be classified as obese which is not the case. Also the body fat % is pretty much an estimation, taken with callipers or measured with impedance scales.

hunnymonster

what ali said plus

If you're given a choice, go with the bf% and get it measured as accurately as possible. A calipers can give a realistic reading if done by someone with experience. It probably most useful but to track changes rather than give an absolute value. I'm not a fan of the impedence measurements. I do a lot of exercise so my hydration levels vary a lot. I've had values varying by more than 10 % in 24 hours on these types of scales. My BF can usually get the calipers reading within 2 %.

BMI is the quick-n-dirty method often used by the medical profesion. It's outdated and whole groups of people (athletes, asian) do not fit the criteria. However, to work it out, take your mass in kilograms and divide it by the square of your height in meters. e.g. me 62 kg/ (1.63*1.63) = 23.3

cowzerp

bmi is outdated and useless as its purely weight based, as a trainer i dont believe in calipers as i've seen so many people using them wrong including top trainers and fitness freaks! handheld body fat devices done right can be very accurate-the right info has to be put in and then it must be done before exercise when your at normal hydration levels, also done on an empty stomach the good hand held body fat devices are accurate within 4% but i believe if used right then you will get an accurate reading-i dont like clients doing there own as they hold them wrong and put in wrong info etc..the other problem with calipers is they are easy to lie to clients if you dont get the result that they want! the body fat reading can also tell if your gaining or losing muscle mass if you know how to read them.

okgirl

Thanks for the clarification. So it's the body fat % I should be concentrating on. I go to curves and got my 1st bf% 2 months ago. It was 21.2%. On sat I got my latest result which was 22.2%. I am not sure if this is accurate as the girl said that even having breakfast could change the result. My diet is mainly low fat, low carb and high protein. With the exception of the weekend vices I am eating healthly. I do allow myself a potatoe or two at the weekend and a few other treats. Somethimes the whole keep fit thing can be very disheartening. I need to increase my matabolism in order to keep the body fat down. How???:(

hunnymonster

by adding muscle mass. Muscles consume energy even at rest or so I've heard :-)

justsomebloke

with a 2 month time scale the mirror test is your best bet. If after 2 months you don't look somewhat better then chances are you aren't doing enough. As the others have stated there are many problems with both BF% and BMI.

okgirl

thanks jsb,
Actually that inspires me as I do see a difference btw now and Two months ago. I am definately more toned on biceps, pecs and have lost almost an inch accross my back. I could benifit from some ab crunches though. :rolleyes:

rubadub

okgirl wrote:

I could benifit from some ab crunches though. :rolleyes:

Time would be better spent doing squats

I am not sure if this is accurate as the girl said that even having breakfast could change the result

I take it this was an electronic scales, they are very unreliable.

I need to increase my matabolism in order to keep the body fat down. How???

Eating 6 even size, evenly spaced meals a day, and lifting heavy weights will raise your metabolism.

okgirl

rubadub,
ta for that, I do hate doing the crunches but have noticed a difference when I put my mind to it. Actually have a really thin day today. Feel and look great. But I do find thats short lived. I think I will take your advice and put some squats into my routine. At the moment I am walking (fast pace) about 4-5km 3 mornings a week and go to Curves 3 times weekly. I usually do a 20 min session using weights to concentrate on upper body. Diet wise I am cutting out as much pricess food as possible Mon-Fri. Eating healthy and drinking plenty of water. Today I feel the benefits!! Yipeee!!!:D

okgirl

rubadub,
ta for that, I do hate doing the crunches but have noticed a difference when I put my mind to it. Actually have a really thin day today. Feel and look great. But I do find thats short lived. I think I will take your advice and put some squats into my routine. At the moment I am walking (fast pace) about 4-5km 3 mornings a week and go to Curves 3 times weekly. I usually do a 20 min session using weights to concentrate on upper body. Diet wise I am cutting out as much process ed food as possible Mon-Fri. Eating healthy and drinking plenty of water. Today I feel the benefits!! Yipeee!!!:D