Losing excess weight is one of the most popular personal goals in the modern world, and the most popular tool we use to measure weight loss is the trusty bathroom scale. But therein lies a problem: what most of us are really trying to lose is “fat”, not “weight”, and a scale won’t measure fat.

One of the best ways to lose fat and get in shape is to follow a healthy and nutritious diet, while at the same time undertaking a high intensity workout routine to burn fat and develop a strong and slim physique. But whatever your diet and workout regime, it’s essential to measure progress, and a scale will only get you so far.

One of the problems with measuring overall weight as you progress with a workout program is that not only do you lose fat, but you gain muscle. Your overall weight loss is less than the amount of fat you’ve lost. You may mistakenly conclude that you’re not losing fat fast enough, when the opposite may be true.

Another problem with measuring overall weight is that any measurement will fluctuate throughout the day as water and solids enter and leave your body. For example, the average person will pass 4.5 pounds of water through their body each day. The water that exits the body is not replaced immediately or precisely, resulting in weight fluctuation. This is why it’s best to always measure your weight first thing in the morning, as part of your pre-breakfast morning ritual, so that you can minimize the variables.

A third problem is that some diet regimes may cause rapid initial water loss. You may think that you’ve lost a lot of fat because you’ve lost quite a few pounds of body weight. However, the actual fat loss you’ve experienced may be far less.

Scales are still a useful tool, and it’s good to know your body weight. But to measure fat loss, you need a better tool. The best tool to use is a caliper, which takes advantage of the fact that most fat is deposited directly below the skin. Measure the fat below the skin at various points on your body, and you can get a fairly accurate measurement of your overall body fat percentage. Calipers take a bit of practice to use accurately, but the concept is simple: pinch a fold of skin and fat away from the muscle and bone at a specific point on your body, and measure its thickness, then look-up the value in a table to get your body fat composition. One drawback with using calipers is that if you want to be thorough, you’ll need somebody else to take the measurements for you, because it’s impossible to reach some of the places you need to measure on your own (such as the area below your shoulder blade). You can skip the places you can’t reach, but accuracy will suffer as a result.

Another option, which is more convenient but not as accurate as calipers is a “bioelectric impedance analyzer”. This is an electronic gadget that you hold in your hands, or step on, that passes a tiny electric current through your body. Since fat is more electrically resistant than muscle, the analyzer can measure the resistance it encounters, and infer your overall fat composition. The advantage of these devices is that they’re easy to use – just hold onto it and look at the digital readout. But they do suffer from inaccuracy compared to calipers. Furthermore, they’re also very sensitive to hydration.

Of course, you can always just opt for simple techniques, like using a tape measure to measure the circumference of your waist, thighs, or other fat-storage areas, or even just trying to fit into your skinny jeans, or being able to comfortably tighten your belt one more notch. They may not be as accurate at measuring fat, but they sure do feel good when you achieve them, and really, they’re what most of us are aiming for anyway.

In conclusion, when measuring fat loss it makes sense to use multiple techniques. By all means, step on the scales and measure your overall weight, and also keep track of your waist measurements (and any other areas that store fat). But if you can, it’s worth getting some calipers or a bio-impedance device, because at some point your waist will stop getting narrower, and your weight may stop decreasing, but that doesn’t mean you’ve stopped losing fat, and the only way you’ll know is if you use one of these other measurement techniques.