This percentage on the body >€εfat scale may not be→₽★' exactly the same as what you thin≤♣k.

Once, I was talking to som↔≠‍♦eone who had just taken a body fat t€♦♥πest. He has cleaned his diet and has₩δ‌✘ been in the gym for about three≠± months. He lost weight >∞¥and fitted his clothes bet≈®♠ter, especially at the waist. He&‌>#39;s stronger in th$±γe gym and can see signs ofε'©λ new muscles in his chest, should€×₽ers and back. But he was in a dilemma.→✘↕• That's because the body↑≥•φ fat test (he just dropped $125) show™βs that he's worse now thα✔∑an he was three months ¶±ago.

"I'm fatter now thaδ↔π n I was on the last s<ε≠₽can!" He said. "H♦∏λ ow can I lose my muscl✔>es? Can you look at my diet and trainin​¶g program and see what I did wroφγ∏ng? "That's what I t δ≈old him: the problem may lie in your diβ♥ε•et. Maybe your train &♦ing plan needs some modifications. Ho♦₹®<wever, there is a third p₹♦αossibility - the result of b∏÷✔ody fat testing is the wa>♠y out.

In fact, most body fa←σ≠t tests, whether they a↕<←re body fat scales, underwater weigh•εing, or even DEXA (X-ray scans com¥≠± monly used to measure bone miner≤‍∑al density), cannot r‌$γely on tracking changes"φ in body composition over time. Usi₹∑→ng the results to guide your trainin✘¥₹✔g and dietary decisionsπε< may lead you completely in the wrong ←δ≈βdirection.

Why should you be alert to₽λ body fat scale testi‌₽→ng?

First, no body fat test ca€÷n tell you exactly how much muscle ∏$ε>and fat you have. The ₽←∏only way to really measure bodπ≠y fat is to peel off all the fa¥>t, put it on a scale and we$ igh it. This method i≈>♣ s very accurate. The only disadvantage λ±is that you have to die to achiφ<eve it. To explain James Kri↕Ω☆φging, the founder of gravimetry, the∞' body fat test is not a "<✔♦♥test" at all. Think of it as a pr÷↑≤ediction rather than a measure♦¶ment.

"When weather forecasteλ®γrs give you forecasts, they don&#∑✔→39;t measure the weather,&q™÷₽uot; Krig explained. "They are f±∞orecasting the weath®§er. That's exactly what happens §↔ when you have a fat test in yo÷α↕εur body. Just as weather for±±ecasters can't predict$÷♦£ the weather 100% accurately, we‍♦  can't predict your body fat φ±level with 100% accura€€♥→cy. "

Let's take the body fat scale as an"♣§ example. They are one of the mos£''±t popular ways to track fat loss andαα muscle growth, mainly because theyε• are cheap, fast and ↔♣φ↑easy to use. The body fat scale ≥σuses a method called ×σδΩbioelectrical impedance, which involv> ♥es running photocurrent in you☆§ ≠r body and measuring the resistance±• ∑ (or impedance) of the current flowβ$÷.

The first and perhaps most₩$≥ obvious problem with body fat quality ♥♥is that they miss most of φ¥"∞your body. For example, ♣γπstanding on a body fat scale wit✘≥h a set of feet to theΩ±↓ feet, the current moves f∞₩rom one leg up and downβ∑ ₹ to the other. This means that you onl ≈y measure the fat content in←φ¶& your legs.

Research shows the content of body fat ∑↓→§scale

The argument in support of body fat t✘§esting is that even if a given te↕‍st is inaccurate, at leas§$φt it is consistent. In other wor∑πδds, it doesn't matter h×↑≤πow many percentage points the bod"¥​y fat test "drops out" here o∏∏©αr there. As long as λ₩☆it is consistent, you can use it to ∏¶track your progress. However, whe•♣← n researchers tested the idea, the ​≠• results were not impressive.

In a study published  ​€in the Journal Sport↕∑s and Sports Medicine and Science,☆¥©< scientists studied changesΩ‌> in body composition in a φ group of male bodybuil' φ$ders. They compared se÷$₹€veral body fat tests -≠§‍ including bioelectrical impe™×dance, techniques us®βed in body fat scales - with th→✘•¥e so-called four-compartment model, whi<§∏ch is the current benchmark for body cΩ omposition and the standard for ÷>ααmeasuring other body fat£§εΩ tests.

Researchers have found that bioele©≈♥≈ctrical impedance is the ≠<‍least accurate of all methods. In fact,α™≤ the error rate is as high as 8%. Let ↑'s say you stepped on some body f→∞ at scales and they told you¥" that your percentage of ₽≠>★body fat is 20%. You eat©♥ well, train for months, and loδ§λse about 5% of your bod€♦y fat. But when you t÷♠ake another test again, the sca' le may show that your p‍∑÷ercentage of body fat has not changed  ‌✔at all.

The same is true of muscle★×π  growth. You can get 5 to 6 poun™£ds of muscle in a few months. But sc™'>ales may indicate that yoλπσ​u don't get any muscle at all. You "≤π₩get the impression tha€★≈t whatever you do to prod♥ •uce these results doesn't work, α♥¶but it does. And you risk giving up th€§§≈e training and nutrition pro→×≠grams that are in op₹®eration and replacing them with less&φ≠± efficient ones.

Can X-rays better test body f©≤©at?

How about other body f™©Ω©at scale tests, suchγ£↔★ as DEXA scans? Are they doing a β÷&​better job? DEXA is the abbr'€✔eviation of dual-energy X-ray abs≈γ§₹orption measurements, which is reasonab→₩le in estimating the average gr→€₹oup. However, over time£​, it is not good at t€☆λracking individual changes i♦€n body fat and muscle mass. Why is t≤εhat? DEXA may overestimate half of ÷ your group's body fat p✔÷δercentage by 5%, while the≈™ other half underestimate by™→ 5%. When viewing gro σup results, the average €♠error size is zero. But individual'₹ results are the way out.

The fact that body fat t✔λεests do well in estimating gr¶φδ≈oup averages does not necessarily m​‌±ean that they are equally good at♣✔ tracking personal progress. When λ‌♣∞Purdue University researchers compar‍↓ed DEXA with the gold'®'≤ standard four-compartment model↔→‍, the results were mixed. In ∑βsome people, the res"<≤>ults are very close. But ≤♠in other ways, they've go∏φ ↕t a way out.

According to the four-compartment mod↔αel, a participant gained 5% body f•εat, but DEXA showed a 5% drop. Accor€¥ding to the four-compartment mo∞ del, another lost nearly 10% of↓δ®ε his body weight, but only 3% o↔∑¶←f DEXA. DEXA is not cheap. A single≈× scan costs up to $100. If you do a se∏>✘cond scan in a few m↓✔onths, that's $100. Iγ♠ε☆f the results don't tell you ≈♦☆∑anything useful, it will cost a lot of®∏✔ money.

Some argue that back-to∏♦-back DEXA scans "prove" ✘₩>↕that they are accurate. That i∑←&s, if you scan yourself and then retu"✔Ω✘rn to the same machine the next ↕‍>day and do another scan, the re&♠÷×sults are almost the¶∏‌​ same. But that doesn't tell you th"₹✘♦at scans do a good job of es±€timating your body composition.δ> It tells you how close the estima§≤tes are to repeated measurementαβ ♦s. It doesn't tell you  "how accurate these estimat±±∑es are.

Some of the techniquesπ≤δ≠ involved in body fat tes→ ting are still catching up•±γ<. Commercial body fat testing equipm♦₽∞ent is inaccurate, and y"♥λou can't use this information tΩφ★o better decide what t•♠εo eat and how to train. ε©→Believing only in the results o&↔f body fat tests, you may evλ€‌δentually think that your diet and t¶<✔raining program doesn'≥♣α★;t work when it really ex¥ ÷&ists - or when it doesn'tσ ✔✘ exist.