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Estimating and Calculating BodyFat Percentage

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Bf

Male and Female Body Fat Guide

Body fat percentage is a better indicator of fat loss than the scale, which simply indicates weight loss.  Weight loss simply lumps lean body mass with fat loss, so it's not the best indicator of progress for those seeking to retain LBM and lose fat. Please check the FAQ for frequent questions about bodyfat found on /fit/ that are answered here.


Calipers, or Skin Fold MethodEdit

Recommended Method, Cheap, Decent accuracy.

Calipers, or skin fold method.  This requires that one buys a fat caliper and learn how to take proper measurements of skin folds. There are many calipers that are cheap that will give you a decent guide to body fat %.  A basic guide is found here, on livestrong.com.

Bioelectric Impedance AnalysisEdit

Not Recommended. More expensive than calipers, not as accurate.

This requires a special scale that runs an electrical current through your body.  Fat is not as conductive as muscle.  It calculates bodyfat on this impedance level, but this can be thrown off by hydration levels, so it is not very accurate.  Most scales are 50 dollars or more.

AnthropometricEdit

Only recommended for those who want a quick estimate of body fat %, 
or those who don't care to buy calipers.

This method is utilized by the US Navy but is considered not very accurate.  It takes measurements of several parts of the body to estimate bodyfat %.  Recommended to find a rough guess of what your % is.  Costs nothing- all you need is a measuring tape, or a peice of string you can wrap around and then measure against a ruler. There's a comprehensive calculator here.

DEXA ScanEdit

Recommended, Expensive.  Only useful for those who really want to know a precise %.

DEXA (Dual Energy X-ray Absorptiometry) scans are accurate but can be expensive (150-200 dollars). They x-ray your body and are able to not only calculate fat mass, but locate where it is stored as well with great precision. This can be done when getting down to lower levels of bodyfat, if one is interested enough to know for sure their body fat %.

Hydrostatic weighingEdit

Recommended, Expensive.  Only useful for those who really want to know a precise %.

This involves being submerged into a tank of water and seeing how much you weigh in the water, as muscle is more dense than fat. This is very accurate (+/- 1.5 %), but expensive as well, running from 100-250 dollars per test.

EstimationEdit

General eye estimation is highly inaccurate as many factors affect how one appears to look.  Body fat % is a precise emperical measurement.  Asking online what your body fat % is very misleading and probably will vary anywhere from 5-10%. Lighting, water retention, angle etc all will effect how much fat it appears you have.

FAQEdit

I'm ____lbs and at __% bf, how long will it take me to get to ___%bf?

Assuming a perfect diet/exercise routine then one can calculate the time it takes to get to a bf% by calculating the amount of fat their body fat percentage equals.

For example:

A male at 180 lbs (81.6 kg) at 15% bf wishes to get down to 10% body fat.

180 lbs x .15 = 27 lbs of body fat. Alternatively, 81.6 kg x .15 = 12.24 kgs.

Now that we know how much fat composes our body in pounds/kilograms, we can see how much fat in pounds/kilograms at are target body fat percentage.

180lbs x .10 = 18 lbs of body fat. Alternatively, 81.6 kg x .10 = 8.16 kgs.

So we take current body fat in pounds/kgs and subtract from goal body fat in pounds / kilograms.

27 lbs - 18 lbs = 9 lbs of body fat to reach goal. Alternatively, 12.24 kgs - 8.16 kgs = 4.08 kgs to reach body fat goal.

At 2 lbs a week of fat loss (or .9 kgs), which is considered maximum amount of fat loss at a healthy rate, then it should take 9 lbs / 2 lbs per week = 4.5 weeks. Alternatively, 4.08 kgs / .9 kgs per week= 4.5 weeks.

TL;DR: Simply put, find current and goal body fat percentage in pounds or kilograms. Subtract them and then divide by 2lbs / .9 kgs a week (or divide by expected fat loss per week desired).

This makes assumptions that you will lose constantly at the rate divided at by the end which is not always true. It does not account for water retention or for metabolic slowdown from long peroids of reduced caloric intake. If this occurs, some suggest to ramp up calories to maintaince, or slightly above (+200 calories) to get your metabolism up again. This occurs after 4-12 weeks of reduced caloric intake, depending on the person.

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