The FastDay Forum

Since you did such a great job with the TDEE/BMR calculation in the tracker, I wonder if a body fat percentage calculation based on gender, height, weight, and waist measurement would be useful? Here is a site that has one:

http://www.healthyforms.com/helpful-too ... entage.php

I don't know the math offhand, but I could search around (or I'm sure PhilT knows it off the top of his head... ) if we decide it would be nice to have as a part of our super-whamadyne progress tracker, at least for peeps like me with no BF% scale and no desire to buy one.

Found this:

http://home.fuse.net/clymer/bmi/

"The percentage body fat is calculated for males as 100*(-98.42 + 4.15*waist - 0.082*weight)/weight and for females as 100*(-76.76 + 4.15*waist - 0.082*weight)/weight."

there's a BMI to body fat correlation too which would give an indication.

Oh and while I'm suggesting things for the tracker, could you place a link to Carorees' post on where to measure your waist (viewtopic.php?f=7&t=1019) right next to the waist measurement fill-in block where you add in tracker data?

[Moogie]

Thanks for these suggestions, I can certainly look at adding these in though will need to figure out where the extra brackets go in the body fat calculation, am guessing:

100*((-98.42 + (4.15*waist) - (0.082*weight))/weight)
100*((-76.76 + (4.15*waist) - (0.082*weight))/weight)

I hate when brackets like that get left out, I mean it could also be:

(100*((-98.42 + (4.15*waist) - (0.082*weight))/weight
(100*((-76.76 + (4.15*waist) - (0.082*weight))/weight

or

100*((((-98.42 + 4.15)*waist) - (0.082*weight))/weight)
100*((((-76.76 + 4.15)*waist) - (0.082*weight))/weight)

or any number of other combinations...

Since you did such a great job with the TDEE/BMR calculation in the tracker, I wonder if a body fat percentage calculation based on gender, height, weight, and waist measurement would be useful? Here is a site that has one:

http://www.healthyforms.com/helpful-too ... entage.php

I don't know the math offhand, but I could search around (or I'm sure PhilT knows it off the top of his head... ) if we decide it would be nice to have as a part of our super-whamadyne progress tracker, at least for peeps like me with no BF% scale and no desire to buy one.

I tried this and it said I have 39% body fat but my new scales say I have 32% body fat, a critical difference wouldn't you say?

[Moogie]

It told me I have 23%, but my scales give me 30% at the mo!

I would love an accurate calculator too. I get very different results on different sites hence i've not been updating the info on my tracker because I can't remember the site that I first used.l

The percentage body fat is calculated for males as
100*(-98.42 + 4.15*waist - 0.082*weight)/weight

and for females as 100*(-76.76 + 4.15*waist - 0.082*weight)/weight.

I'm not seeing a brackets problem - same number of ( and ) ?? The above are valid equations.

To break it down a bit :-

fat mass = -98.42 + 4.15 * waist - 0.082 * weight
fat % = 100 * fat mass / weight

HTH

Here's another from http://www.scientificpsychic.com/fitness/diet.html

The formula for men is:
%Fat=495/(1.0324-0.19077(log(waist-neck))+0.15456(log(height)))-450

The formula for women is:
%Fat=495/(1.29579-0.35004(log(waist+hip-neck))+0.22100(log(height)))-450

obviously needs more data input

and finally, one that can be implemented with existing BMI etc data :-

Adult Body Fat % = (1.20 x BMI) + (0.23 x Age) - (10.8 x gender) - 5.4

where male gender= 1, female=0.

(none of the brackets are necessary LOL)

I would love an accurate calculator too. I get very different results on different sites hence i've not been updating the info on my tracker because I can't remember the site that I first used.l

I'm not sure we can do "accurate" but I am in favour of this site having calculators so we all refer to the same one and the debate can be about the problem rather than the statistic !

[Moogie]

The percentage body fat is calculated for males as
100*(-98.42 + 4.15*waist - 0.082*weight)/weight

and for females as 100*(-76.76 + 4.15*waist - 0.082*weight)/weight.

I'm not seeing a brackets problem - same number of ( and ) ?? The above are valid equations.

To break it down a bit :-

fat mass = -98.42 + 4.15 * waist - 0.082 * weight
fat % = 100 * fat mass / weight

HTH

Maybe I was just taught differently or am just still a blonde under all this hair dye, but to me the equation isn't clear - are you dividing the bracketed stuff by weight and then multiplying that result by 100 or are your multiplying the bracketed stuff by 100 and then dividing by weight? Not to mention all the stuff in brackets which could be grouped in any number of ways without brackets to make it clear:

-76.76 + (4.15*waist) - (0.082*weight)
-76.76 + (4.15*waist - 0.082)*weight
(-76.76 + (4.15*(waist - 0.082)))*weight

Even these need brackets in my eyes:

fat mass = -98.42 + (4.15 * waist) - (0.082 * weight)
fat mass = -98.42 + (4.15 * (waist - 0.082)) * weight
fat mass = -98.42 + (4.15 * (waist - (0.082 * weight)))

Depending on the groupings, they will give different results.

fat % = (100 * fat mass) / weight
fat % = 100 * (fat mass / weight)


Am I the only one who works like this? Is it not normal to group parts of equations with brackets? It's certainly necessary when coding!

have programming languages deteriorated to the point where they can't do maths properly !

You are filling the equations with surplus brackets. a = 100 * b/c works fine and has no scope for going wrong in any way mathematically.

The "precedence of operators" means that all the multiplications and divisions are done before the adds and subtracts.

Hence correctly implemented a - b*c should always come out as a - (b*c) and never as (a -b) * c


As you're reinforcing my prejudices about maths and women, and possibly blondes, I'm off to watch a Carol Vordeman video as penance. Won't help with the blonde thing though !

but to me the equation isn't clear - are you dividing the bracketed stuff by weight and then multiplying that result by 100 or are your multiplying the bracketed stuff by 100 and then dividing by weight?

Maths 101 - it doesn't matter, the outcome is the same !! The sequence of multiply and divide doesn't affect the outcome

5 * 2 / 10 is the same as 5 / 10 * 2