Blog Post

How To Measure Changes In Body Composition: A Guide

Tracking body composition, scan data

There are so many ways that you can track changes in body composition and measure progress over time. 

All of which have their pros and cons.

So this blog post will go over each of the main options you have for tracking changes. 

What Is Body Composition?

Body composition refers to the composition of your body mass. With predominant components being lean mass and fat mass. So body composition is the ratio of the two.

Now lean body mass refers to not only muscle but also includes

  • Bone
  • Organs
  • Skin 
  • Body water 
  • And literally, anything that isn’t fat mass 

When people say they would like to improve their body composition. That typically means gaining muscle mass and/or reducing body fat. And if we really want to get specific, most people are referring to skeletal muscle in particular. 

Either way, ideally in tracking changes in body composition and overall progress, we would have some idea of the ratio of fat to skeletal muscle mass over time. 

Body composition methods compared

How Can We Track Changes in Body Composition?

Weight On The Scale 

Weighing yourself is one of the easiest ways to track progress. Other pros of this method include the fact it is cost-effective, can be done frequently, and often doesn’t even require leaving the house. 

However, our body weight does not always tell the whole story when it comes to body composition. Obviously, it does not provide data on how much of your body weight is made up of fat mass versus lean mass. 

But you don’t always need this data.

For example, if your main goal was to lose body fat. You would expect to see a downward trend in body weight over time. Which can be tracked using body weight alone.

On the flip side, if you were gaining muscle mass in a calorie surplus and therefore gaining weight over time. This is also something that could be tracked by body weight.

The main piece of information you would be missing in these two scenarios would be the composition (fat versus muscle) of the weight you are gaining or losing. Which could matter to you or it may not. 

The other complexity is in the case of body recomposition. Which refers to losing body fat and gaining muscle mass simultaneously whilst body weight remains relatively consistent. 

If body weight is remaining the same, outside of normal fluctuations, but there is a composition shift happening, clearly that cannot be tracked through a body weight scale. So if recomposition is the goal, another way of tracking progress would be better for you. 

One of the biggest things to mention about bodyweight is that fluctuations and changes in weight will occur. Your body weight will change depending on a range of things that have nothing to do with actual fat/muscle mass gain or loss. 

Things such as 

  • Sodium intake
  • Fluid intake
  • Fiber intake
  • Food volume
  • When you ate last
  • Changes in hormones around the menstrual cycle 
  • Bowel movements and urination

Can all impact your body weight.

So it is best to either take frequent weights at the same time of each day and compare weekly averages. Or just be aware that each time you weigh yourself, there is bound to be a difference based on the above things alone. 

Waist Circumference 

Probably the second most accessible way to measure changes in body composition is by using a waist circumference measurement.

Typically significant changes in waist circumference are going to be indications of either gains or losses of body fat.

So if you are trying to lose weight/fat and improve leanness, taking waist circumference every 2-6 weeks can give you some indication of progress.

Waist circumference can be useful in the case of body recomposition as you will likely see your waist size change even though your body weight is fairly consistent. 

It can also be used when bulking (actively gaining bodyweight to optimize gains in muscle mass) to gauge body fat changes. For example, if measurements are going up rapidly around the waist, that would infer that body fat is increasing significantly.

One of the issues with waist circumference is that bloating can affect your results. So that is something to keep in mind. Especially for those with IBS who experience extensive bloating at times and people with a menstrual cycle who may experience bloating and distention during their menses. 

All in all, waist circumference is typically used alongside bodyweight to get a better understanding of potential body composition changes. But it is not without its flaws. 

Skinfold Test

Skinfold tests are very common. A lot of coaches, nutritionists, dietitians, and personal trainers offer them as a service. 

This practice involves measuring several sites across the body with a set of calipers to gauge a person’s body fat percentage. 

The benefits of skinfold tests are that they don’t require any large, expensive equipment, and places that offer them can be found relatively easily.

However, accurate skinfold measurements are difficult to do and are unlikely to be consistent unless the person doing them is highly trained and does them frequently enough to maintain their skill level.

There are even courses and accreditations available for this one skill alone known as an ISAK accreditation. 

Even still, you likely will want the same trained professional to measure you each time since there can still be a pretty significant difference between providers of this service. 

Nonetheless, when done well, skinfolds can be a useful way to track changes in body fat (increases and decreases). So maybe beneficial in the case of recomposition or wanting to have some idea of the composition of the weight you are gaining/losing. 

But something to note is that they are not validated for people who are above a “normal” body fat range and are more accurate on relatively lean individuals. 

Bioelectrical Impedance Analysis 

Bioimpedance scales

Bioelectrical Impedance Analysis or BIA measures the rate at which a low-level electrical current travels through your body. Based on that rate, a calculation is used to estimate fat-free mass. 

In conjunction with other information such as your height and weight, it can estimate your overall body composition.

A lot of gyms and similar facilities will have BIA machines. InBody is a common BIA service in Australia that is transported to different gyms so that they can offer their members regular body scans. 

There are also smart scales available for your home that use the same concept as BIA. 

The issue with BIA is that it can be very inaccurate and is impacted by other variables including hydration level, recent intake of carbohydrates and sodium, the menstrual cycle, and even room temperature.

So to get comparable results over time, you would have to keep your food and fluid intake very similar in the days leading up to each scan. 

There are likely going to be some BIA machines that are more accurate than others but overall I don’t often recommend them. I would instead opt for something like a DEXA scan which is more accurate and usually around the same price as a good quality BIA scan. 

Dexa Scan 

Dexa scan

Dexa machines are considered the gold standard for assessing body composition. They are relatively accurate compared to other methods and can give you objective numbers on how much lean mass and fat mass you have. 

They also can indicate bone mineral density. Dexa scans are often used for the diagnosis of osteoporosis and osteopenia. 

The cons of using this method of tracking body composition include:

  1. They are more expensive than other options (ranging from ~$50-$200)
  2. They are less accessible, especially in regional areas 
  3. You usually do them infrequently (once every 2-12 months). So they won’t be able to provide frequent data to track progress. 

They also aren’t perfect and are mildly impacted by changes in body water and other variables.

Nevertheless, to measure larger changes in body composition they are great options. 

And then you can use other methods more frequently to track short-term progress and make adjustments to your nutrition plan on a regular basis.

Appearance & How Your Clothes Fit 

Sometimes you don’t need numbers at all to assess changes in body composition and track progress.

Going by how you feel, look, and how your clothes fit is a completely valid way to make assessments. 

For some, this non-numbers-based system can be a lot less triggering than things like daily weighing, skinfolds, and DEXA scans. 

Although they are less objective ofcourse.


As you can see, there are a lot of ways you can track changes in body composition over time. 

In practice, I usually have my clients using multiple methods of tracking. 

For example, we may use daily weights to compare weekly averages, do DEXA scans every 3-6 months, and use a monthly waist circumference.

Other clients, however, may be simply going off look and feel to measure progress over time.

It is all going to be a personal choice and will depend on your goals and exactly what it is you would like the measure.

By Leah Higl

Leah is an accredited practising dietitian from Brisbane. She also competes as an under 75kg powerlifter with Valhalla Strength Brisbane. As both an athlete and dietitian, she spends much of her time developing her knowledge and skills around sports nutrition, specifically for strength-based sports. Although, she works with a range of athletes from triathletes to combat sports and powerlifting. Leah also follows a plant-based diet and her greatest passion is fuelling vegan/vegetarian athletes and proving that plant-based athletes can be just as competitive as their non-vegan counterparts.​