The Truth About Bathroom Scales: Hint – You’ve been lied to!


Have you ever watched an episode of “the biggest loser”? I used to love watching the much anticipated weekly weigh in’s where the biggest losers are crowned and the not so biggest losers are well.. forced to work harder the next week!

We are constantly being led to the bathroom scales to see how much fat we’ve burned and how much of an impact that last cheat meal had on progress. But, what if the scale weight wasn’t so accurate after all? What if we were putting way too much pressure on dropping weight on the scale and we were sacrificing other important areas of measurement?

Before I get started, don’t get me wrong here.. you can probably see where i’m going with this, I beleive measuring scale weight is fundamentally important for tracking progress and identifying weekly / monthly patterns.

However, it’s important to understand other areas of why the scale goes up and down, for instance the scale can randomly change for various reasons including:

  • Extra carbohydrates consumption (glycogen stores in the muscles and liver)
  • Additional water weight through hormonal changes, glycogen changes or sodium increases
  • Increases in Lean Body Mass (aka muscle)
  • Digestion of certain foods
  • Bone Density (this has the smallest impact on overall weight changes & the hardest to measure)

As you can see from the above list, there are other impacts of scale weight changes which can fluctuate at different times.

Water / Glycogen & Food Residue

Most of the time weight changes on the scale are a mixture of water, glycogen and food residue being digested slowly through the gut (which can make up 1.5-3kg depending on your diet).

The slightest changes in your diet can result in huge changes to the scale, for instance if you are following a fairly healthy diet, low in sodium, low in sugar, low in refined carbohydrates, and suddenly you ingest 3 slices of pizza on the weekend. You could gain up to 3-4kg of excess water weight.

Each gram of glycogen (carbohydrates) stores 3-4 grams of water, this almost always explains a sudden increase in scale weight, this sets of panic in most eyes because all the sudden you feel bloated and full.

These sudden changes in glycogen are the reason women suddenly feel “bulky” when they start working out, because their muscles suddenly have more water & glycogen stores. This is also the main reason people lose weight quickly on a low carb or ketogenic diet.

Fat & Muscle

Although short term changes can occur as discussed above, the overall body composition changes should only be defined by muscle gain & fat loss. If you are only trying to drop body fat, then you should be focusing on tracking muscle loss / gains & fat loss.

  • Muscle Gain Goal: Increase lean body mass while minimizing body fat gain
  • Decrease Body Fat Goal: Decrease body fat % while maintaining or slightly increasing lean body mass

The process of dropping body fat while increasing lean body mass is called body recomposition, I recommend starting the 90 Day Fitness Model Challenge if you want to focus primarily on this goal. 

For this reason it’s important to think of tracking scale weight for identifying long-term patterns, water weight changes are short-term changes and should not be associated with tracking body composition.

For women to achieve sustainability with any physique goals, I recommend focusing on dropping body fat levels while increasing lean body mass (muscle), in my experience this is the most sustainable method for body composition changes.

Alternative Tracking Methods

When we talk about Body Composition what we are really talking about is the overall body fat % and the remaining lean body mass. For example:

  • If your body fat % is 30% then the other 70% will be lean body mass
  • If your body fat % is 20% then the other 80% will be your lean body mass also

It’s important to understand that body composition changes can also occur while the scale weight stays the same or increases slightly. Two women can have the exact same weight yet look very different, one woman may have a lower body fat % but have higher levels of lean body mass.

Circumference Measurements (tape)

Not many people realise it, but you can actually get a very good reading of body fat % from a measuring tape, a decrease in circumference with different body parts is a very good indication that your body fat % is decreasing.

One thing to keep in mind when using tape for measuring body composition changes, always mark the same spots for measuring. Even the slightest change in location will cause significant differences with results. For this reason using a marking pen each time can help ensure you are measuring the exact same areas.

Skinfold Calipers

This is generally the most commonly used by personal trainers and physique coaches these days. Calipers are typically accurate, however they do have a 2-3% error rate, for this reason I always recommend using caliper readings as a baseline and to review each body part reading in patterns over time rather than the total (overall body fat % reading).

Dual-Energy X-Ray Absorbitometry (DEXA)

The thing I love about DEXA scans, is the in-depth body composition results you receive from each scan. Not only will you be able to have a very accurate reading of your body fat % and lean body mass, but you can also measure bone mineral density.

DEXA scan clinics are becoming more and more popular, meaning the higher prices involved for the general public is decreasing. After and before my physique / fitness competitions I always have a DEXA scan completed to show my body fat levels and specifically my increase / decreases in lean body mass.

It’s important to note with DEXA scans, the differences between skinfold readings is quite significant, for this reason you should understand that if you are using both methods at the same time, you will have mixed readings. A better alternative is to choose one method or the other, to avoid any confusion with readings / body composition results.

Wrapping It All Up!

As you can see there is a lot more involved when it comes to your typical bathroom scale! The key notes take home from this blog are:

  • Scale weight should be tracked by looking for long-term patterns rather than short-term changes
  • Short-term changes in scale weight can be manipulated easily by hormones, water, glycogen and digestion
  • Body composition should be tracked only by body fat % and lean body mass
  • Measurement tapes, Skinfold calipers and DEXA can all be utilized for body fat %
  • A DEXA scan will be the most accurate for measuring body fat, lean body mass and bone mineral density

Hope this cleared up some myths about scale weight, let’s start becoming more aware of short-term and long-term weight changes!

Happy lifting!