Body fat testing, ranked from worst to best
Every now and then, someone steps on a fancy scale at a roadshow, gets told they are at 35% body fat, and walks into the PIT Singapore looking like they just got retrenched.
Relax lah.
Before you panic over a number, you should know HOW that number was produced, because some of these methods are about as trustworthy as your friend’s “I’m ONLY 5 minutes away”.
So let's rank the common body composition methods from worst to best, and I'll tell you exactly what we use for our personal training and diet coaching, and why.
1. BMI, the most jialat one (Worst).
BMI is just your weight divided by your height squared. That's it. It measures zero body composition. It cannot tell the difference between 90kg of muscle and 90kg of Char Siew Bao.
The pros? It's free, it's instant, and it works fine for tracking populations of millions of people.
The cons? For any individual who actually trains, it is useless. Next.
2. Bio-impedance machines (the smart scales and InBody types)
These are actually clever pieces of tech, so let me explain how they work, because understanding the mechanism tells you exactly how to use them properly.
The machine sends a tiny, painless electrical current through your body, usually foot to foot on a scale, or hand to foot on the fancier InBody-style units. It then measures the resistance the current meets along the way, and that resistance reading is the core of the whole measurement.
Here's the key principle. Water conducts electricity well. Fat conducts it poorly, because fat cells hold very little water. So when the current flows through you easily, the machine reads lots of lean tissue. When it meets resistance, it reads fat. It takes that resistance reading, combines it with your height, weight, age and sex in a prediction equation, and produces your body fat percentage.
Now, the one thing you need to understand before trusting any single reading: the machine is estimating from your body water. And muscle is about 75% water, which is exactly why lean tissue conducts current so well. That means a body holding extra water and a body holding extra muscle look very similar to the machine. Drink two litres of water and your "muscle mass" nudges up on the printout. Sweat through a hard session or wake up dehydrated, and the numbers shift the other way. Nothing actually changed in your body composition. Just your water.
This is why readings move around with anything that shifts your body water: hydration, your last meal, sodium from last night's laksa, or where you are in your menstrual cycle. In practice, the error margin on any single reading runs around plus or minus 5% to 8% body fat. We've had clients worried they gained fat overnight after a laksa dinner. But that's just water and sodium doing their thing. Your body composition barely moves in 24 hours: This is important to remember.
So is bio-impedance useless? Not at all. It's fast, painless, cheap per test, and completely beginner friendly. The trick is using it correctly: measure under identical conditions every time, same time of day, fasted, similar hydration, and follow the trend over weeks rather than reacting to any single number. Used that way, it's a perfectly reasonable tracking tool. Just don't let one Sunday morning reading ruin your week, because the day-to-day swings are mostly water, not fat.
3. Tape measurements (the US Navy method)
Measure your height, neck, waist and butt (For women only), plug it into a formula, out comes a body fat percentage. It's free and honestly not bad for tracking trends in untrained people, which is why the military uses it to screen thousands of recruits quickly.
The problem is it assumes everyone stores fat in the same standard pattern. Muscular individuals, very lean individuals, and anyone with a non-textbook fat distribution will get skewed numbers. Decent screening tool, not a measuring tool.
4. Skinfold callipers, what we use at the PIT
Now we're talking.
Callipers measure the thickness of your subcutaneous fat at specific sites on your body. Done properly, this is the smartest field method in existence for people like us.
Here's the part most people don't realise: the real value of the callipers is not the final percentage. It's the trend. If your sum of skinfolds is going down week after week, you are losing fat. Full stop. No hydration games, no laksa-induced panic.
But there's a catch, and it's the biggest one with this method: the accuracy lives and dies with the experience and skill of the tester. Grabbing the fold at the wrong spot, pinching too much or too little tissue, or reading the calliper too early or too late, and the numbers drift. Two different testers measuring the same person can land several percent apart. This is a skill built over hundreds of measurements, which is exactly why a calliper in untrained hands is worth less than the smart scale we just talked about. In experienced hands though? When I compared our calliper protocol against a DEXA scan, we landed within 1% off the DEXA reading.
But I'll be honest with you, because I don't over promise here, callipers have real limitations, and one of them matters a lot in practice: they get genuinely difficult on larger individuals.
Why callipers struggle on larger bodies
A calliper works by pinching a fold of skin and fat away from the muscle. On a larger client, that fold can be thicker than the calliper jaws can even open. Beyond a certain point, you physically cannot get a clean measurement.
I’m sorry: I spent the last 30 minutes thinking of how to not sound potentially offensive describing that scenario and that’s REALLY the best that I could come up with.
It's also much harder to lift a proper fold in the first place. The fat doesn't separate cleanly from the underlying tissue, the fold compresses differently, and the tester's error grows with every millimetre of thickness.
On top of that, the prediction equations that convert skinfolds into a percentage were mostly built on leaner populations, so the further you are from that range, the shakier the maths.
So at the PIT, if a client is carrying more weight, we don't pretend the callipers are giving us gospel. We lean on other markers, waist measurements, photos, how the clothes fit, gym performance, and if you really want a hard number, we refer you out for a DEXA scan. Then as you lean out, the callipers become more and more reliable, and we switch over. Right tool, right time.
One more limitation for everyone, big or small: callipers only measure the fat under your skin. Visceral fat, the stuff wrapped around your organs, is invisible to a pinch. That one you'll need imaging for.
Which brings us to the Gold Standard…
5. DEXA, the best you can realistically get
DEXA uses low-dose X-rays and gives you the full picture: body fat percentage within roughly 1% to 2%, regional breakdown (left arm vs right arm, trunk vs legs), visceral fat, and bone density thrown in for free. Several clinics and imaging centres in Singapore offer it.
Two caveats.
First, it costs real money per scan.
Second, different machines can shift the result, so if you're comparing scans over time, Always do them at the same clinic. Don't scan at one place in January and another in June and then WhatsApp me in a panic. Sure kena pluck.
The methods you won't find in Singapore anyway
A few other methods deserve a mention, mostly so you know why I’m not sending you to them.
First, the Bod Pod. You sit in an egg-shaped chamber and it calculates your body volume from air displacement, accurate to around plus or minus 2% to 3%. Sounds great, but Singapore doesn't have one available to the public, and even where they exist, the reading gets thrown off by body hair (Sorry Angmoh guy friends and Makkals), clothing, and each test costs real money. Good tech that hasn’t made it to our shores.
Then the true gold standards which we also don’t have access to.
Hydrostatic weighing, where they dunk you in a tank and weigh you underwater, needs a dedicated dunk tank, a full underwater exhale, and a facility willing to run it, and there simply isn't one offering it commercially here.
The 4-compartment model combines multiple lab tests and lives strictly in research settings, and an MRI body composition scan costs more than most people's monthly gym budget many times over.
Unless you're a subject in a university study, these are not options, and honestly, you don't need them. DEXA is more than enough precision for any real-world goal.
Our recommendation:
DEXA once or at most twice a year for the absolute numbers, callipers and measurements in between for the trend. That combination is honestly all anyone needs.
Apart from cost, here’s another 2 reasons for not doing DEXA too often:
1. Radiation
2. What the f#@k for?
The bottom line
Stop chasing the perfect number and start chasing a consistent method. A trend measured imperfectly but consistently beats a one-off measurement from the fanciest machine. That's why our personal trainers will pinch you with callipers at the PIT instead of putting you on a smart scale, and why we'll tell you straight IF the callipers aren't the right tool for your body at this stage.
Want to know where you actually stand and, more importantly, where you're heading? And MOST importantly HOW to head in the right direction? Come down to the PIT Singapore and let's do it properly. Drop us a message and let’s take it from there.
Author: Henson Irving, PIT Director
