Which is Better: BMI or Body Fat Percentage?

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Which is Better: BMI or Body Fat Percentage?

March 8, 2007

Many people are confused when it comes to looking at their Body Mass Index (BMI) versus their body fat percentage, since they do not always agree. So which should you go by?

First of all, body fat percentage is an estimate of the fraction of the total body mass that is fat mass, as opposed to lean body mass (muscle, bone, organ tissue, blood, and everything else that makes you work). This index is often used as a means to monitor progress during a diet or as a measure of physical fitness for certain sports. BMI is just a simple measure of the weight of a person scaled according to height.

That being said, body fat percentage is a much more accurate way to measure excess body weight than BMI since it differentiates between the weight of muscle and fat, while BMI just lumps it all into one figure.

So why are there so many BMI calculators on the internet? This is simply because measuring body fat percentage requires a few things: Special equipment, the physical presence of the person wishing to have their fat evaluated and the physical presence of someone who knows how to work the equipment. BMI is just a loose guideline for anyone curious about where they sit, but it is not a one size fits all answer. Curious about your body fat percentage? Then talk to a fitness professional at your gym or even your doctor. Curious about your BMI? Then check out [sorry, shameless plug] the Fit Calculator.

To read what the body fat percentages mean, read more

Description	Women	Men
Essential fat	10-13%	2-5%
Athletes	14–20%	6–13%
Fitness	21–24%	14–17%
Acceptable	25–31%	18–25%
Obese	32%+	25%+

5 Comments

puddinpie 6 years 10 weeks

^I think they're pretty accurate. I remember a trainer telling me I should drink a glass of water about an hour before getting on the body fat scale to get an accurate reading.

reeveske 6 years 10 weeks

peachy, those scales send a electrical-type pulse through your body which they use to detect lean vesus fat mass. it can be affected by how hydrated you are, since dehydration gives you a high body fat measurement, because the current is slowed down, as it does with the more fat that is in your body. it is also affected by food intake and skin temperature.

PeachyPietra 6 years 10 weeks

Body Fat % is defintely much more important, but its so hard to measure on your own. Does anyone know how accurate those readings on the scales that measure body fat % are?

reeveske 6 years 10 weeks

yeah i learned in kinesiology class in college that BMI gets really skewed with really athletic and muscular people (like football players), cause of what Fit said above, with them lumping both lean mass and fat mass as one thing. They are considred overweight, when they are really just very muscular.