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stupid question please explain

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stupid question please explain

Postby sunshine » Mon Dec 10, 2007 10:51 pm

Could you please explain to me the difference between bmi and body fat percentage, or are they the same? Sorry to be so clueless :D
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Postby Misstoodles » Tue Dec 11, 2007 12:44 am

:) It's not a silly question at all.

BMI stands for Body Mass Index, and it is used as general way of telling if a person is underweight, normal, overweight or obese. The problem with BMI is that its calculated by height and weight alone. It doesn't take into consideration the persons frame or organ, bone, fluid and muscle mass.

An example would be.. say two people each weighed 70kg and were the same height as one another. They would have the same BMI, but one has less body fat and is more muscle than the other, making the reading a rather crappy way of determining how much more weight you should lose.

This is why body builders go by body fat percentage, because their aim is to lose body fat, and gain muscle. If they were to use the BMI test, they'd be considered obese, lol!

Body Fat Percentage is alot more accurate. Your body fat percentage is measured using a tool called a Caliper. Ever heard of a pinch test? Same thing. They pinch various different parts of your body and then measure (with the tool) your fat. They then determine your overall percentage from all the measurements they took.

They would then say, X percentage of your overall weight is fat, and the ideal body fat percentage range is such and such, so you could lose X amount of fat to come within a healthy fat percentage.

This is just an example. But say you were 70kg and your body fat percentage was roughly 30%. Roughly 21kgs of you would be made up of fat, and 49 of lean body mass. But it's generally considered healthy for a woman to have between 20 and 25% body fat. So the idea would be to lose 5-10% of your excess fat, or 3.5-7kgs of pure fat. Putting you at 63-66.5kg with a healthy amount of fat.

See how this is far more accurate to the individual than a BMI test?

Sorry if this seemed like a longwinded rant to you, I just wanted to explain it properly:P
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Postby losebabyfat_2005 » Tue Dec 11, 2007 8:11 am

grrr stupid body fat!

I'm 35% body fat and I weigh 56kg! I've still got to lose 5 kg of pure fat to get me to 25% ( i think). I've only lost 1.86kg of pure fat in 6 weeks! even though I've lost 3 kg... although i do need to go to the gym more often.

Any ideas for helping me burn the fat?!
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Postby rivenriver » Tue Dec 11, 2007 8:25 am

Can I add a question?

If I don't have the kind of scales that measure body fat, where can I find it out?

And does anyone know what % is "normal" for obese people? (ie, me?)
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Postby SarahC » Tue Dec 11, 2007 8:30 am

I'm the same, low weight and high body fat (well, I think it's high, it's hard to know for sure) :(

I was going to ask that same question lol. How does everyone else measure their body fat? And which would be the most accurate measure? I have the body fat scales at home, but they almost always say 35% or something outrageous like that. I have digital calipers that say like 21%, and that's assuming I'm doing it right :?
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Postby losebabyfat_2005 » Tue Dec 11, 2007 8:46 am

i got mine measured at the gym.

But i also went to some website (can't remember what it was called) and it told me i was only 19.5% body fat. It went by waist, hip and neck measurements. I don't think that takes into account my loose skin though
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Postby rivenriver » Tue Dec 11, 2007 8:54 am

I just found a website too, it went off hips, waist, neck and height, and told me my % is 41, and that my ideal weight is 79. But 79 is a bmi of 24.9. :shock:
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Postby sunshine » Tue Dec 11, 2007 2:26 pm

Thanks everyone, I appreciate your replies. I understand it now, because according to my bmi I am obese!!! But actually I am a size 12, weigh 67 kilos but only 5'2, so that would be why I am classed as obese by the bmi WTF??

My body fat % has come down to 42.9 so I have still a way to go to get in the healthy range. Man I wish I was about 5'11 then I would look very slim, but since I am so short, it shows!! Cheers everyone :D
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Postby Misstoodles » Tue Dec 11, 2007 2:51 pm

Umm I think at gyms you can get it done, but you can purchase Calipers on Ebay and do the skinfold tests at home, and use online calculators for it.

Infact my brother has one that I want to borrow.
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Postby rivenriver » Thu Dec 13, 2007 8:25 am

sunshine wrote:Thanks everyone, I appreciate your replies. I understand it now, because according to my bmi I am obese!!! But actually I am a size 12, weigh 67 kilos but only 5'2, so that would be why I am classed as obese by the bmi WTF??

My body fat % has come down to 42.9 so I have still a way to go to get in the healthy range. Man I wish I was about 5'11 then I would look very slim, but since I am so short, it shows!! Cheers everyone :D


:shock: That really shocks me, that someone who is a size 12 and 67kg could be obese. That's one reason why bmi annoys me too. Eat more calcium, grow taller! ;) ;) :P
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Postby Haylez » Thu Dec 13, 2007 8:29 pm

I've been the same weight for a year and have lost over 10% body fat and haven't gained any muscle (I've actually lost some muscle mass). WTF?

I don't like the pinch test. Last time I had one done they squeezed to hard and drew blood.
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% Body Fat
Start: 36.3%
Current: 35.4%
Goal: 27%


1st mini Goal: 80kg by christmas
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Postby sunshine » Thu Dec 13, 2007 8:37 pm

Rivenriver, I would LOVE to be taller, my husband is over 6'2 and my 6 yr old daughter is well on the way to being taller than me. So out of my family of hubby and 3 kids, I think I am going to be the short one :(
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Postby Fireball » Fri Dec 14, 2007 1:02 am

When I studied human anatomy at Uni yaers ago, they said the most accurate body fat % was measuerd in water. If measurements were made using callipers the formulas used to work it out determine accuracy. It would be reasonably accurate if you belonged to the same "population as the formula was worked out using, i.e. your characteristics were the same. eg. age, censored, econmic background, education etc. The more refined, the more accurate. Although that was a long time ago, I suspect the scales just give a rough idea. I've never used them to see how they operate, but how do scales know if you weigh a certain amount because you stuff yourself on cream puffs or if you are muscular from lots of exercise?

Haylez - I've heard you lose muscle mass if your body is forced to use energy from that source instead of being able to break down fat. I think this is due to not taking in enough energy from food for the amount of exercise you do - your body will take the most accessible form of energy if it is in need.
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Postby Haylez » Fri Dec 14, 2007 8:24 am

Yeah if you're body isn't getting enough food it will hold on to as much fat as it can and start taking food from muscle and your organs will start shutting down. Scary Stuff. Which is why I'm going to start having 1 meal a day and replacing the other meals with shakes, just to try and bring my kilojoules up. So I'm now intaking about 5000kJ a day, which I know is still not a lot, but I'm not planning on staying on the shakes for long.
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% Body Fat
Start: 36.3%
Current: 35.4%
Goal: 27%


1st mini Goal: 80kg by christmas
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