The interest in bodyfat estimation is not unreasonable, particularly for the novice who needs an estimate of lean mass for dietary needs and goal planning.
When I began, I had NO idea what to do, now much protein I needed, what my target weight was... most folks don't.
That being said, a rough ballpark is sufficient. Put simply, suppose you know you're fat, you now weigh 200 lbs and the last time you looked okay you weighed 170. You probably want to get down to 10% bodyfat (although you may not know this, you just want to see abs), so you try a few methods to test your bodyfat. Since very little muscle is likely to be gained while cutting, let's just assume zero net change for this parameter.
Calipers at your local gym put you at 22% bodyfat.
(156 lbs lean mass; weight at goal: 173 lbs; protein target >156g daily, fat target >78g daily)
Some online thingie puts you at 27% bodyfat.
(146 lbs lean mass; weight at goal: 162 lbs; protein target >146g daily, fat target >73g daily)
My "rule of thumb" method,
on my blog puts you at 23.5% bodyfat, which you may then enter on my "
bodyfat cut calculator".
(153 lbs lean mass; weight at goal: 170 lbs; protein target >153g daily, fat target >77g daily)
Unsatisfied, you get a DEXA, which puts you at 21.5% bodfat.
(157 lbs lean mass; weight at goal: 174.4 lbs; protein target >157g daily, fat target >79g daily)
These various estimates tell you the following:
- Your % bodyfat is somewhere between 21.5% and 27%
- Your lean mass is somewhere between 146 lbs and 157 lbs
- Your weight at a goal of 10% bodyfat will be between 162 lbs and 174 lbs
- You need to drop between 26 and 38 lbs
- Your protein minimum is between 146g and 157g daily
- Your fat minimum is between 73g and 78.5g daily
If you underestimate your current lean mass, you'll eat about 11g less protein then if you overestimate your current lean mass.
If you underestimate your lean mass - or somehow manage to gain a bit while cutting - you'll hit goal sooner than you think.
Those of us who have been at this for a while intuitively know this, but for the novice, let's just say it might be helpful to have it spelled out a bit.