How does the BMI chart work?

myiceisonfire
myiceisonfire Posts: 782 Member
in Health and Weight Loss
I was 37.6 when I started MFP, now I'm 32.1.

I lost 5.5 "something".... What's the "something"
Does that mean I lost 5.5% of my body fat?

edit: typo

Replies

  • katm427
    katm427 Posts: 227 Member
    BMI points. That's all they are.
  • myiceisonfire
    myiceisonfire Posts: 782 Member
    BMI points. That's all they are.

    That doesn't really answer my question
  • Keltinator
    Keltinator Posts: 265
    bmi is based on height and weight, so it basically means you lost weight.

    for example, a person that's 5'7" who weighs 150 pounds will have a lower bmi than someone who's 5'3" and weighs 150 pounds.

    hopefully that helps a bit.
  • myiceisonfire
    myiceisonfire Posts: 782 Member
    Nevermind.... =/ I guess I just don't know how to ask the question
  • katm427
    katm427 Posts: 227 Member
    BMI points. That's all they are.

    That doesn't really answer my question

    I meant it entirely as an answer. It's not body fat percentage because you would need to have measurements and weight and height for that. BMI is a BMI point. The closest thing I can find online is that it is a relative proportional measure of mass, but it has no indication of muscle, bone, or other body tissues, so yeah. Wikipedia says: "The formulae universally used in medicine produce a unit of measure of kg/m2." I don't know if that would help.
  • withchaco
    withchaco Posts: 1,026 Member
    BMI points. That's all they are.

    That doesn't really answer my question
    That's what it is, though. BMI charts do not correspond to your body fat %. It's just a numeric scale representing the ratio of your height to weight.
  • auntie_missy
    auntie_missy Posts: 113 Member
    BMI is an index of your height to weight. BMI doesn't account for age, gender, race, etc. It's not a direct percentage, and doesn't distinguish between fat, water or muscle. Therefore, it's not a very accurate way to gage your progress. What it is good for is very rough guidelines for underweight, healthy, overweight, and obese.
  • myiceisonfire
    myiceisonfire Posts: 782 Member
    Where do I go to figure out how much body fat I've lost then?
  • katkins3
    katkins3 Posts: 1,360 Member
    First of all, congratulations on your weight loss so far. I hadn't thought about the BMI, what it really means, but now that you mention it, it seems a bit vague to me too.
    We have a digital scale that tells both weight and fat percentage. I think body measurements are good feedback too. Even blood pressure can tell you if you are improving!
    You are doing great though, so keep it up!
  • withchaco
    withchaco Posts: 1,026 Member
    Where do I go to figure out how much body fat I've lost then?
    http://en.wikipedia.org/wiki/Body_fat_percentage

    Several methods listed there... some of which require high tech equipments!

    Most people seem to either use a digital scale that measures body fat percentage (which I don't trust), or a caliper pinch (never used one myself, but heard good things about it).
  • myiceisonfire
    myiceisonfire Posts: 782 Member
    Found a body fat calculator at... http://lowcarbdiets.about.com/library/blbodyfatcalculator.htm

    With height & measurments I was 60.2% when starting MFP ... now I'm at 54.9%
    That's 5.3% of body fat I've lost! =)

    So maybe the mbi chart gives "general" or "vague" numbers for body fat?
  • MadBabysMama
    MadBabysMama Posts: 373 Member
    Basically it means you're getting closer to a healthy weight, according to current medical standards. Obesity is defined as BMI of 30 and above, while overweight is between 25 and 29.9; once you're between 18-25 on the BMI chart, you will be at what is considered to be the healthy weight range for your height. It's a rough metric that does not take into account body composition, etc., as others on here have noted, but a lot of medical professionals use it to loosely estimate healthy weight. Congrats on your great improvement in BMI, keep up the great work!
  • crisanderson27
    crisanderson27 Posts: 5,343 Member
    Found a body fat calculator at... http://lowcarbdiets.about.com/library/blbodyfatcalculator.htm

    With height & measurments I was 60.2% when starting MFP ... now I'm at 54.9%
    That's 5.3% of body fat I've lost! =)

    So maybe the mbi chart gives "general" or "vague" numbers for body fat?

    No, it is totally unrelated to body fat. I have a BMI that puts me in the borderline obese range, with 18% bodyfat. Another person my height, with less dense musculature and/or bone structure, might have as much as 35% bodyfat or MORE at the same BMI.

    This is what makes the BMI chart completely and totally WORTHLESS.

    ~EDIT - Additionally, those online calculators are virtually worthless as well. Go to a gym, and pay them to take your bodyfat % with a caliper.
  • solpwr
    solpwr Posts: 1,039 Member
    BMI is a standardized ratio of height and weight. Think of the body as a cylindrical object. Weight increases proportionally to the square of the height. Or something like that.
    Functionally, it is a number that provides the relative circumference of the cylinder.
    The limitation of it is that all "cylinders" are not the same. It works fine for a huge population of data. The distribution of the population should be similar.
    And when you apply it to yourself, it will show weight loss. But so will the scale.
    The very best way to know progress is by clothing sizes, in my opinion.

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