Why you should focus on your body fat percentage instead of weight!

I’m obsessed with body composition. Body composition refers to the percentage of fat, muscle, and bone in your body. Having a good body composition means you’ll be healthy, feel, and look your best. Who doesn’t want that?

There are several ways to figure out your body composition and guess which is the best? Your eyes. Unless you’re dead, that is, and someone strips you of your tissues and weighs them separately. All other methods vary in accuracy. But don’t despair. There are ways to substantially enhance their accuracy and I’ll show you how in this article, as well as why focusing on your weight is rarely a good use of your time, especially when you’re a light person or weigh yourself every day to predict weight loss progress.

In order to figure out exactly how to best assess your body composition, I did four of the tests below under the same circumstances within a 24-hour window to achieve the most accurate results to verify they were indeed worthwhile.


  1. Bioelectrical Impedance Analysis (BIA)
  2. DEXA scan
  3. Skinfolds
  4. Underwater weighing
  5. Bod Pod
  6. Circumference with weighing


I began with the BIA method. Most health clubs use a BIA machine, mainly because they’re cheap and accessible. If used under ideal circumstances AND combined with skin-fold measurements, these two methods can give you very accurate results, especially in tracking your progress adding or subtracting fat and/or muscle mass.

BIA machines send an electrical current through your body that measures the density of different tissue, then uses an equation based on results derived from large groups using underwater weighing according to Weightology.net.

It appears BIA is suitable for “normal” populations, meaning people who aren’t very over or underweight, provided you follow all the guidelines to get the most accurate result. BIA isn’t particularly accurate for obese individuals, as it tends to underestimate body fat and overestimate muscle mass for that population. Often, body fat is overestimated in lean individuals. Check out this website for more detailed information regarding this.

I did this test 30 min after waking up on a 16-hour completely fasted stomach, which is the ideal time to do it. I wasn’t dehydrated or on my period (in other words, not bloated). I was constipated, however, which put my weight slightly higher at 146 pounds at the time. (For reference, the next morning, it was 144.5.) I’m 5 foot 7.5 or 171 cm tall. According to the InBody, I was 22.3% body fat with 113.8 pounds of lean mass (water and dry lean mass, mainly muscle).

DEXA SCAN (dual-energy x-ray absorptiometry)

Three hours later, I did the DEXA scan. Because the DEXA isn’t as sensitive to hydration, I drank a big coffee and a liter water on my way to the scan. That made me gain 3.1 pounds in three hours. Folks, see how easy it is to fluctuate the scale! Please, especially you women who are more prone to water weight due to hormonal changes. Don’t solely rely on the scale for weight loss.

Back to DEXA. These days, this expensive method, using X-rays to scan your body, is considered the gold standard in body-composition assessments, meaning most accurate. It’s the only method that will show where on your body you carry your fat and your muscle mass, which is one reason I’ve been so eager to do it. Check out my scan below and my selfie next to it. The yellow at the edges is my body fat, the red muscle mass, and white bone.

Selfie of me day after DEXA scan so you can compare the image.
My very unflattering DEXA scan image. (I’m lying down here.) You can clearly see that the vast majority of my fat is around my hips and thighs, which comes as no surprise to me.

According to my DEXA scan, my body fat percentage was 23.8 %. At first I was confused when the technician said it was very good. LiveLeanRX, the company that did my scan, has an ideal body fat chart. Women 41-60 were considered healthy with a body fat percentage range between 23-35%. I’m 51. Other DEXA scan companies use the same chart, but being right below 35 % body fat percentage is not healthy at any age. (Check out this body fat chart for more accurate ranges.) This leads me to believe that A) DEXA scans use a higher percentage compared to other body fat charts in general for reasons unknown. Or B), it’s a small error as DEXA scans tend to overestimate body fat by 3-4 % and underestimate muscle mass by up to 7 pounds. See HERE and HERE for science on that. Or C) I’m just fatter than I’d thought. The good news was, my lean mass was 113.9 pounds, which is practically identical to the InBody, suggesting Equinox’s BIA machine is very good at predicting lean mass (muscle). Yes, I was more hydrated when I did my DEXA, but not so much to make a dent on the scan. In order to see even a slight change, you’d need to drink at least a gallon of water right before the test. Go HERE for more on cheating on the test. I’d drunk about 1.5 liter over three hours, which isn’t that much. But even a cup of liquids will show on the scale though, remember that!


Later in the day, I did skin folds. Fasted stomach or hydration levels don’t matter for this method, but don’t do it after working out, as moist skin will make it harder to pinch your skin. This method using calipers is another popular method trainers use because it’s cheap and accessible. Your trainer pinches your skin in 3-7 separate body sites depending on the particular calculation used–there are more than one–and measures the folds. After the measurements are added together along with your age, they’re entered into an equation to determine your body fat percentage.

Skin-fold testing is by far the most accurate when done on lean individuals. Think elite-level athlete lean. Makes sense, right? The more fat on/in your body, the harder it’ll be to measure. Add in visceral fat–think protruding belly–that one can’t even touch. Things like the tightness of your skin and the skill of the trainer will significantly effect your result. Having personally performed thousands of skin-fold testings, the tendency is to underestimate especially women’s body fat content. I’ve underestimated it on myself too. Currently, my skin fold measurements are 19.1 %. I used to think I was about 17 % until I took a hard look at my body and compared the number to my DEXA scan result and our BIA machine, the InBody. Then I redid my skin folds and realized I had been too light on my hands when separating the fat from my muscles. I don’t believe I’m as high as near 24 % because I have eyes to see with–remember, best gauge to determine body composition is your eyes. Plus, I have tons of experience assessing bodies and their compositions. However, my legs aren’t super lean, so 17 % never made sense to me. But not 23-24 % high either. My higher total body fat percentage makes more sense when you consider my body type, though: longer legs, shorter torso. Most women, including me, carry their fat on hips and thighs. Longer thighs=more space for the fat to “grow”, so more total body fat. The DEXA scan doesn’t take into account whether you’re long or short-waisted. Check me out below. You can see my ribs, collar bones, and definition on my abs, thighs and shoulders. At almost 24 % body fat, you wouldn’t see much definition anywhere. So between 19- 20 % body fat percentage seems more accurate.

Pic taken day after DEXA scan. Zero filters or edits. 146 pounds and 5′ 7.5″. Since you can see I’m lean–clothing size 4-6 depending on the clothing company–I hope you now understand that a light weight doesn’t necessarily mean you’re healthy.


I chose not to use this method as it’s no longer as reliable as the DEXA scan but equally as expensive and far more complicated to execute correctly. Also, it’s no longer considered the gold standard of body composition assessments, which is another reason I didn’t bother with it. To learn more about this method, go here.


The Bod Pod uses the same principle as underwater weighing except it uses air to determine the density of your body tissues. Apparently, the error rates of this method, especially when tracking progress, are too big to be reliable. According to Weightology.net, “One of the reasons the Bod Pod is worse than underwater weighing is because there are more variables that can affect the results.  For example, facial hair, body temperature, moisture, and the tightness of the spandex or swimsuit can all alter the results.” Go here to learn more about how Bod Pods work.


I have a pair of 25-inch non-stretch jeans that I love but are too tight for me at the moment. My goal is to get in to them soon! They’re the perfect tool to gauge my body-fat losses. I strength-train regularly to maintain muscle mass (lean mass), so I don’t worry about that part of my body composition. When they fit me well, I know I’m where I want to be body fat percentage-wise, which is a clothing size smaller than my current one. I tried them on the same day as the tests above, and they’re, predictably, still too tight. Sigh…

Use the methods I’ve described above to assess your body composition. Because DEXAs are inconvenient and expensive (between $150-$250 in NYC), use the InBody with skin folds to achieve the same results. This article should now have taught you that your body weight or BMI are not as important as your body composition. Chances are, if you’re a woman with a light weight (think around 113 pounds at around five foot four and a low BMI) and have cellulite, you’re skinny fat. The cellulite is key as 90 % of women have at least some. You need more muscle and less fat on your body. I see this regularly with female clients. If you’re a man and weigh more than you think you should, check out your stomach. Is it flat and you can see definition? If so, your body composition is probably okay. If you can’t see much ab definition, you need to lose body fat.

If you don’t have access to skilled trainers and a gym, the best way to track your progress is by using a pair of old-school tight-fitting jeans or snug-fitting dress pants and try them one periodically. This works for both men and women as most men carry their fat around their waistline (so a guy can focus on the pant’s waistline primarily) while most women carry their fat around butt, hips and thighs.

Obviously, don’t wash the jeans and put them on right after drying them. They’ll be smaller and make you think you’ve gained weight. Conversely, don’t stretch them out by walking around with them for hours, as they’ll become too big and you’ll think you’ve lost weight when you haven’t.

You can of course use a measuring tape, but it’s hard to measure in exactly the same place and use the same exact tension when wrapping it around your limbs. Which is why snug-fitting, stiff pants are the best combined with weighing yourself once a week.

To predict progress, let at least 8 weeks go by before you measure again–using the same method under exactly the same conditions–mainly because tracking errors in individuals can be up to 3-5% over time using these machines. You can try on the jeans more often to judge progress. I recommend to let at least two weeks go by before you try them on again, though.

My next article will be about how to go about building your muscle to the size you want AND your genetics will allow. Sign up to my newsletter so you don’t miss it!

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