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Measure Up: BMI vs. Body Fat Percentage

BMI and body fat percentage are weight-loss terms thrown around with little explanation, so if you're confused about what they mean or which you should pay more attention to, you're not alone. Here's a brief primer to help.

BMI stands for Body Mass Index. It's a simple measure of the weight of a person scaled according to their height. You can use Fit's Calculator to determine your BMI, or follow these steps:

  • Multiply your weight in pounds by 703.
  • Divide that answer by your height in inches.
  • Divide that answer by your height in inches again.

A healthy BMI is between 18.5 and 24.9.

Body fat percentage is the weight of a person's fat divided by the person's weight. It lets you see how much of your body is made up of fat, and how much is bone, muscle, blood, and organs. There are several ways to calculate your percentage. Your skin folds can be gently pinched with calipers, some high-tech scales can measure body fat, and there's also underwater weighing. Many people get their body fat percentage measured if they are into sports or trying to measure their progress while losing weight. Fit women should have 21 to 24 percent body fat. Female athletes have between 14 and 20 percent.


To find out which one you should be concerned with


Body fat percentage is a much more accurate measurement in determining if you are healthy. BMI doesn't take into consideration how much of your weight is muscle and bone and how much of it is fat. So that means a person can have a healthy BMI, but still carry weight in their belly, which can increase their risk for heart disease. So if you're trying to lose weight, or just wondering if your current weight is healthy, it's worth seeing someone to have your body fat percentage measured.

Srividhya Srividhya 5 years
AZDaisy AZDaisy 8 years
Thanks Spectra! I appreciate it :)
Spectra Spectra 8 years
gumdrops33--I didn't really mean it that way; I meant that I'm heavy for my size...not sure if that makes sense, but what I kind of meant was that many people see me and think I only weigh about 95-100 lbs when in reality I weigh 110-112. It just goes to show that weight is not a very good indicator of body composition. I agree that 125 is a good, healthy weight for being 5'3" as well...every body is a little different.
pandacn pandacn 8 years
I'd really like to know my body fat percentage, but haven't found a gym that measures it. I do have a scale that supposedly measures body fat. How accurate are those?
gumdrops334 gumdrops334 8 years
Spectra, I'm 5'3" and 125 and feel completely healthy and fit. I have about 20% BF, which is totally average and healthy. I don't think it's right to say that 110 lbs is "heavy" for someone who is 5'3"
Spectra Spectra 8 years
AZDaisy--Yeah, there's a very high chance that she screwed up somewhere. Given your stats, you're probably more in the 30-35%ish range, possibly lower depending on your frame size. Next time you visit your doctor, ask him/her to use bioimpedence or underwater weighing to measure your body fat. That'll give you a better picture of how much more weight you need to lose.
AZDaisy AZDaisy 8 years
Hi Spectra...yeah she did use calipers, and she did the calculations super quick. The ocd girl in me wanted her to double check, but of course I didn't say anything :-P I'd love to get a more accurate calculation!
Spectra Spectra 8 years
Thanks for posting this! I'm heavy for my size...I weigh something like 110 at a height of 5'3" and I'm really tiny. My husband and I recently were part of a statewide health survey where they measured our body fat using a current that they clipped onto our feet and fingers (bioimpedence). My body fat came back as 16%, which is low for a woman, even though my BMI isn't freakishly low. If I didn't work out as much as I did and weighed 110 at my height, I'd probably be larger in size and my body fat would probably be higher. And you can also be a "normal" BMI and have too much body fat, especially if you have a small bone structure. AZDaisy, how did the trainer measure your body fat? Did they use calipers? Sometimes when they use those, you get inaccurate readings because you have to know EXACTLY how to do it right. It's pretty easy to make mistakes and get readings that aren't accurate.
AZDaisy AZDaisy 8 years
I'm 25, 5'6 and right now, 150 pounds (I've lost 25 pounds since January). My BMI is 24.7. I just had a free personal training session at 24 hour fitness where the trainer measured my body fat, and said I was at 40%. But I've also been told that at the gym they tend to tell you a higher number so that you're encouraged to buy more sessions. Trust me, I could stand to lose a few more pounds, but I find it very hard to believe that my body is almost half fat. And after looking at Allure magazine, where they have the fit challenges, and seeing women who weigh more than me (and appear bigger than me) have less body fat percentage, I don't know who to trust!
Feesje Feesje 8 years
I don't really "believe" in BMI. A friend of mine is very athletic and has a lot of muscle mass, yet he should be overweight according to his BMI. The reason? He's not that tall. Apparently his muscles weigh too much for his height. And my sister-in-law is treated for anorexia right now. She is currently at a very healthy weight (she even weighs more than she did before she was anorectic), yet the doctors force her to eat even more to reach a BMI of 20. However, she is very tall, so she has to eat huge amounts of food to get to that point. Which, to me, isn't very healthy. So BMI: no, I don't buy it.
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