Body Fat Percentage or BMI?

The Sandbox Fitness
1

I’m not a fan of BMI, since it would give a 5’9 220lb football player (say, a fullback) the same BMI as mine.

I found this long time ago, and I’m guessing this is a linear regression best fit formula.
So, if one’s actual body fat percentage is way off the best fit, then it won’t work. However, it should work on a relative basis, and one should understand what is necessary to lose body fat.
In my range, dropping an inch of waist, without lowering weight, lowers BFP by about 2%.
Lowering my weight by 5 pounds, without lowering my waist size, raises my BFP by 0.8%.
so, determine how to do it: eat less, workout more. Done!

Men (Imperial measurements):
F1 = Weight * 1.082 + 94.42
F2 = Waist * 4.15
Lean Body Mass = F1 - F2
Body Fat Weight = Weight - Lean Body Mass
Body Fat Percentage = Body Fat Weight / Weight
I have it in an Excel file for ease of use. Today for me: 22.2%

Women’s calculation is more complicated, 'cause amirite?
F1 = Weight * 0.732 + 8.987
F2 = Waist * 0.157
F3 = Hips * 0.249
F4 = Wrist / 3.14
F5 = Forearm * 0.434
Lean Body Mass = F1 - F2 - F3 + F4 + F5
Body Fat Weight = Weight - Lean Body Mass
Body Fat Percentage = Body Fat Weight / Weight

There are web sites that use this, bt don’t show the formula, 'cause math.

My source, from my Internet Explorer Favorites that were not copied to my Chrome:
https://www.bmi-calculator.net/body-fat-calculator/body-fat-formula.php

But I’d like to know how they concluded these betas, and what the confidence range is.

2

the big * is that body fat distribution is different for everyone, and unless you get lipo, you have no control over it.

but yeah, if you have a belly, you probably fat.

3

I think the formula uses hip measure (and waist measure) as a proxy for most of a body’s fat. The forearm and wrist measures are a counterweight for those.
Again, assuming linear regression, since the formulas are linear.

4

mirror method. do you look fat? LOSE WEIGHT. do you not look fat? cool.

5

Of course it is. As I’ve stated, this formula estimates BFP based on (again, I assume) the most significant linear factors. If you’ve got a big fat-filled right arm (different what is considered “normal”), your actual body fat percentage will differ from this formula.
Gonna have to hit the dunk tank for extreme accuracy.

6

I wish I could go back in time to the first time I thought I looked fat and then gain 20 lbs because I was at least 15 lbs underweight at the time.

7

Okay maybe this does not work

When I got to a weight that I ultimately decided was too big, it wasnt the mirror method, it was pictures on social media where I looked fat. Although my pants size going way up should have also clued me in.

Although after I lost weight, my mother told me I was fat and to never get there again. People avoided saying it to my face

8

I hope your mother didn’t phrase it that way. I hope she also told you that your worth is irrespective of your size and that if you did gain weight again, that’s cool too.

3 Likes
9

My BMI, calculated both by the fancy scale and by my personal trainer’s pinchie-thing, put me in the over 30’s category, and thus obese.

I’m certainly overweight atm, but I’m pretty skeptical about this being “obese” thing.

10

You seem to be mixing body fat percentage and BMI. BMI is purely a function of weight and height. You dont need a fancy scale for that.

https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm

11

This formula confuses me because it seems to count butt fat as bad fat on that hip measurement. Butt fat isnt bad fat though.

Also not even sure where to measure at the hips. Too confusing and I suspect this formula will give me a high body fat %, so I’m sticking to bmi for me. I look best in the low range for normal for my height. I’d rather look at that rough estimate than another also rough estimate that’s even more complicated

12

Yeah, I don’t think a woman hits obesity (30 BMI) until ~40% body fat.

13

I…don’t…even

14

Oh maybe, the scale does both since it knows my height.

My BMI is like 31, and fat is… 36% :frowning:. I don’t think I look obese in any event.

15

there could be fat around your organs if you have high BFP but don’t look obese. that’s actually more dangerous

16

:pensive:

17

or big bewbs

18

Thighs, I think you meant to say thighs here.

19

Top 10 Reasons Why The BMI Is Bogus : NPR.

The person who dreamed up the BMI said explicitly that it could not and should not be used to indicate the level of fatness in an individual.

The BMI was introduced in the early 19th century by a Belgian named Lambert Adolphe Jacques Quetelet. He was a mathematician, not a physician. He produced the formula to give a quick and easy way to measure the degree of obesity of the general population to assist the government in allocating resources. In other words, it is a 200-year-old hack.

1 Like
20

Why do we think BMI is still used by the medical industry?

I don’t think we need an article to tell us that it’s bogus. It’s intuitively bogus, but why is it still used?