Future BF% Estimation

[Guest guest]

Hi folks:

Here are a couple of thoughts for those who managed to pass their elementary algebra exams.

For a long time I used to wonder how far I would need to drop my weight in order to get down to some target BF%. I started CRON with a body weight of about 173 lbs and a body fat above 20%. Ten percent seemed like a sensible BF target to aim at, but I had no answer to what seemed to me to be a pretty important question: "How far will I need to drop my total body weight to get to a BF of 10%."

Of course measuring body fat isn't easy in the first place. But ignoring that little detail let's think about what is involved in making future estimates of this kind.

Taking a few figures at random, suppose you know (believe, suspect, hope, imagine) that your current BF% is 16·4%, and you want to figure out how far your total body weight would have to drop to get to a given level of body fat - say 10% for the purpose of this example.

Below is an equation for you. (If necessary I can supply the simple algebra that arrived at this, but try not to ask please!). It takes as inputs your current total body weight - (lbs); your current body fat, calculated from your total weight and BF% - (lbs); your BF% objective (%); and the factor you decide to use for the proportion fat loss will be of the total weight you lose - (fraction).

Of course we will not all agree on this. Tony, for example, believes that the proportion lost varies with body fat level. But my limited experience, based on the data I have seen, suggests it is a fairly consistent two-thirds, from obesity-levels of body fat down to a BMI of 21.x. Others are free to use their own number, but this equation is only good if you believe that this proportion remains about the same at the levels relevant to your own situation.

Here is the equation:

T2 = (F1 - FAC x T1)/(BFO/100 - FAC)

Where:

T2 is your total weight when you reach your body fat percent objective

F1 is your starting weight of fat (25 lbs, say?)

FAC is the fraction fat lost is of of total weight lost (2/3, for example?)

T1 is your initial total body weight (153 maybe)

BFO is your BF% objective (10 perhaps)

For instance, for someone starting out at 153 pounds, with body fat percent of 16·4%, who is aiming for BF of 10%, and where two-thirds of weight lost is fat, the equation works out as follows:

T2 = (F1 - FAC x T1)/(BFO/100 - FAC)

T2 = (153 x .164 - 0.6666 x 153)/(10/100 - 0.6666)

T2 = (25.1 - 102)/(0.1 - 0.6666)

T2 = 135.7 pounds.

So the result indicates that, based on these assumptions, a BF% of 10% will be reached at a total body weight of 135.7 lbs.

Those who enjoy stuff like this can calculate for themselves that for the same person aiming instead for a body fat of 12%, body weight T2 comes out at 140.7 lbs.

Have fun with this ....... if yer find this kind of stuff fun : ^ )))

Rodney.