Understanding body composition - Anna Pearce

Body composition is the way that we describe what the body is composed of. Most commonly, it is used to discuss body fat, lean mass and water content.

Rather than merely comparing height to weight (BMI), body composition is calculated either through scans or through skin-fold measurements.

Why is body composition important?

Depending on genetics and the kinds of activities you regularly do your weight on the scales and your weight compared to your height (BMI) may not accurately reflect your health.

Muscle weighs more than fat. While some body fat is essential, excess body fat is proven to significantly hinder healthy function in multiple ways.

On the flip side, for most, gaining extra muscle has significant health benefits.

When we exercise we change our body composition. Usually, this is in three ways:

1. Reducing body fat by expending more energy than we have available from our daily food intake.

If our nutrition is balanced correctly, we are in a slight caloric deficit, and we haven’t been doing this for more than a few months consecutively then the body should take the extra energy from stored body fat.

2. Reducing muscle mass by expending more energy than we have available from our daily food intake.

If our nutrition isn’t well balanced, our caloric deficit is too high, or this kind of activity has been continued for too many months consecutively then the body can become catabolic.

This means that energy will be taken by breaking down muscle tissues and is a natural survival mechanism when the body is under extreme stress.

However, it poses serious health risks and should be avoided.

3. Increasing muscle mass by stimulating muscles until they are damaged and need to be repaired.

The desired oucome of resistance training- repairing process builds bigger and stronger muscles.

For someone new to exercise they can gain muscle and lose fat consecutively by being in a slight caloric deficit.

However, for someone who has been training for some time, they would need to be in a caloric surplus to gain muscle.

Note: body fat gain will occur from consuming excess food without including resistance training.

Isn’t a lower weight on the scales an indicator of better health?

If you consider the first two points above, then when it comes to weight on the scales then they are considered equal. However, catabolism is an extremely unsafe and unhealthy state. while body fat loss is generally more desirable, let’s consider the possibilities of increasing muscle mass.

The old method used for weight loss was cardio. Lots of cardio. We now know that sustaining the weekly levels of activity to maintain a lean physique from cardio alone isn’t practical for many people. Additionally, the body is designed to adapt and become resistant to “wasting” energy on a lot of cardio without receiving a nutritional reward.

To continue physical progress, you need to do more and more exercise on a higher intensity level. Eventually, this becomes impossible. Ultimately, activity stops and rapid weight gain follows.

Resistance training is a critical component for sustained weight loss and maintaining fat loss.

Muscles control all movements in the body. They can contract and shorten then relax and lengthen. Lower your arm next to your body and bring your fist up to your shoulder. Touch your upper arm with your other hand while you do this. The muscle on the front of your arm, the bicep, shortens to pull your upper arm up. If you lower your arm slowly, you will feel this muscle gradually lengthen and then relax.

Muscle weighs significantly more than fat and plays a significant role in the body’s ability to regulate blood glucose by storing it. The more muscle, the more glucose can be stored in the muscle as glycogen. The more stored glucose, the better the body becomes at delivering high-performance burst as well as sustaining energy without fatigue.

Why is body composition important to people with a lot of weight to lose?

If people who have a lot of body fat to lose they include resistance training in their weight loss program they may feel discouraged when their weight loss slows. It is essential for clients such as this to have a deeper understanding of how their body is changing. Their fat loss should be continuing (possibly at a slightly slower rate); however, muscle mass should be increasing.

I have seen clients go from losing up to ten kilograms per week gradually slowing to only a couple of kilograms per week. Understanding that their body was still changing at a significant rate was important in maintaining adherence to their fitness program and nutrition.

On the other side of the body composition battle, I have seen another client go through around ten kilograms of weight loss over that many months, then watch her weight start climbing back up on the scales. When I compared her body measurements from her lowest weight with her current weight her body fat % had actually dropped when her weight gained. She had gained around three kilograms of muscle mass.

How can I find out my body composition?

There are numerous ways you can do this. They will range from indicative of a change, an indicative percentage, through to an accurate percentage.

1. Hip to waist ratio:

This is a simple calculation where you divide your waist circumference by your hip circumference. These don’t accurately measure your body composition in percentages; however, they are an excellent indicator of health risk and are preferred over a BMI.

Holding fat around the middle of the body is considered the worst in regards to health. This indicates that fat is being stored around organs. The ratios for men and women differ due to the structural differences in men’s and women’s hips.

Health risk Women Men
Low 0.80 or lower 0.95 or lower
Moderate 0.81–0.85 0.96–1.0
High 0.86 or higher 1.0 or higher

If you are taking these measurements yourself, then don’t be alarmed to see the hip measurement increase with either a static or decreasing waist measurement. This is a positive indication that the muscles in the lower body are growing. The growth in the hip measurement will result in a lower hip to waist ratio.

2. Bicep relaxed to bicep flexed comparison:

Hold your arm out parallel with the floor with your palm facing forwards. Get someone to measure your upper arm circumference halfway between your shoulder and elbow. This is the relaxed measurement.

Next, scrunch your hand into a fist and bend your elbow to flex your bicep. Measure the circumference of the widest part of the bicep. You should avoid doing this measurement within two days after an arm workout because inflammation in the muscle can alter the findings.

However, if body fat is reducing, then the relaxed measurement may decrease slightly. If muscle mass is increasing, then the flexed measurement should improve slightly. A positive result is an increase in the difference between these two measurements.

3. Bioelectrical impedance analysis scales:

These look much like a normal set of scales, however, they put a low level of electrical current through the lower half of the body. Electricity flows faster through water and muscle than it does through fat and bone. You enter your height and age into the scales (to help determine leg length and bone density) then stand on the scales in bare feet.

Bear in mind that accuracy is limited due to variables in the leg to torso length ratios, bone thickness and density, and fat distribution between the upper and lower body.

However, they are consistent in how they measure so if you are tracking your progress on these alone can help you understand if there are changes in body fat and muscle mass. These can range from $40 through to $1000 to purchase, and some gyms will have them available for clients to use.

However, a word of caution: I used these at a previous gym. They gave me a reading of 39% body fat when my skinfold measurements were indicating 17%.

4. Skin-fold measurements:

Skin-folds are measured by pinching and folding the skin and measuring them with callipers. The measurement will represent a double measure of the thickness of the skin. While you can take measurements anywhere on the body there are set places over the body that can either be consistently tracked for changes or can be used in calculations to work out your body fat percentage.

Skin-fold measurements require specialist training to take correctly and consistently and are a tool used mostly by fitness professionals for tracking progress and validating their services. While skin-folds are the most accurate way to physically measure the body, the results are still only indicative.

The callipers can only measure the thickness of skin that contains subcutaneous fat and many people will also hold fat in other parts of the body, particularly around the organs.

5. InBody scan:

These are in the same family as the bioelectrical impedance analysis scales but are a step up in technology and a significant step up in cost. Use of these scanners is offered to customers on a price per use basis.

They can be found in some gyms and health clubs, or available from scanning services specialists. Whilst these results are only indicative, they are fairly accurate and give a good understanding of how fat and muscle are distributed around the body.

They also give some indication of bone density and mineral content; however, they are not reliable enough to diagnose issues like osteoporosis. There are no known side effects of using these scans regularly.

6. DEXA scan:

Dual-energy X-ray absorptiometry (DEXA) scans are based on x-ray technology. by exposing the body to a small dose of ionizing radiation an accurate picture of body composition can be taken. The 3-d scanning technology can show quite accurately how fat, lean mass and bone are distributed in the body, including visceral fat.

Visceral fat is the dangerous fat that sits around the organs and is associated with numerous lifestyle-related illnesses. A manual measurement like the hip to waist ratio will touch on this area, however not in the same accuracy. While DEXA is the most accurate scan the downside is that they can only be performed a few times per year due to the small dose of radiation.

The accuracy of all of these tests can be improved by timing. Take the measurements at the same time of day under the same conditions. Conditions include the same volume of water and food consumed before, the same volume of exercise, the same time of day etc. How much you have sweated or how inflamed your muscles are from your workout can impact your measurements.

The ideal situation would be to measure first thing in the morning, before food and water and the day after your rest or non-activity day.

Interpreting Results.

At the end of the day, while your body composition can be measured and can be indicative of your health and fitness it is not something to obsess on. Different percentages can look quite different on different people and can impact their lifestyle in different ways.

Health and fitness should always be about making you feel great.

Use your results to inform you about how your activity and nutrition have impacted your body. If you want a different result then don’t beat yourself up about the past, learn from it and change direction.

Don’t allow what you are to stop you from being what you want to be.


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by Anna Pearce

Surrounded by her treasured indoor plants and beloved little dog, Anna shares her insights into copywriting, SEO, productivity, and maximising health and life as a remote worker. Between blogs and landing page copy, you'll find her motivating and spreading positivity through health and fitness coaching.

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