Measuring your body composition (or the ratio of fat or non-fat composition of your body) is done for several common reasons, such as trying to increase muscle mass for health or looks, reduce fat mass/percentage for health or looks, or increase bone health to reduce the risk of fracture and hospital stay-related health decline. If your goals are general health and you have no current body composition goals, you still may want to measure your body composition occasionally. Why care about maintaining a healthy body composition?
Maintaining a low-fat mass throughout your life reduces the health impact of the persistent low levels of inflammatory chemicals released from stored fat cells. Maintaining long-term low levels of systemic inflammation reduces the risk of developing many hard-to-manage conditions such as cardiovascular disease, high blood pressure, dementia, diabetes type 1 and 2, osteoarthritis, and depression that can all contribute to reduced quality of life and an early death https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9807546/ Adipokines in inflammation and metabolic disease | Nature Reviews Immunology. Regular exercise also has an anti-inflammatory effect but cannot counter the daily effects of higher body fat. The anti-inflammatory effect of exercise: its role in diabetes and cardiovascular disease control - PubMed (nih.gov). So, in combination with exercise, maintain a healthy body fat content for your health.
Lean mass, or your muscles and bone, as part of your body composition, correlates well with life and healthspan Skeletal Muscle Mass as a Mortality Predictor among Nonagenarians and Centenarians: A Prospective Cohort Study - PubMed (nih.gov) Muscle mass index as a predictor of longevity in older adults - PubMed (nih.gov). Total lean mass also gives us an estimate of your fitness and physical ability better than total fat mass, so it is worth keeping as high as possible. If you have a high body fat content, this may counteract having high muscle mass. Associations of Skeletal Muscle Mass and Fat Mass With Incident Cardiovascular Disease and All‐Cause Mortality: A Prospective Cohort Study of UK Biobank Participants | Journal of the American Heart Association (ahajournals.org).
Ok, so what is a healthy amount of body fat? For females, this is between 15-20% (if sustained, this range should allow a regular menstrual cycle for a pre-menopausal female), and for males, this is predicted as between 10-15% What's a healthy body fat percentage? (mennohenselmans.com) Some studies cite that higher amounts, such as 25% for males and 35% for females, are also fine, so sitting in between each recommendation for each gender seems to recommended at the moment Optimal Body Fat Percentage Cut-Off Values in Predicting the Obesity-Related Cardiovascular Risk Factors: A Cross-Sectional Cohort Study - PMC (nih.gov)
Ok, so what is a healthy amount of muscle mass?
We don't yet have strong research evidence for a healthy amount of muscle mass. Future studies might strengthen recommendations to have a “fat-free mass index” of around 25 (see here for your calculation of this). More importantly, preventing “sarcopenia” or the sedentary lifestyle and age-related loss of muscle size, quality, and function, will reduce high rates of disability, loss of independence, institutionalisation, major healthcare and dependence costs, and early mortality Sarcopenia and health-related quality of life: A systematic review and meta-analysis - PubMed (nih.gov) Sarcopenia is measured by movement testing (see here). Being as strong in your upper and lower body and as aerobically fit as possible for the rest of your life is a good surrogate measure of having a “healthy” amount of lean mass. Still, it is also an even better surrogate for overall health.
“OK, so how do I measure my body composition the best?” Well, answering that question is the purpose of this article. A healthy body composition is being in the recommended body fat ranges while having as much lean mass as possible. Only a few methods are truly practical in terms of cost, time, and access. These can be used to predict a healthy fat and lean mass and measure your rate of change if you are actively trying to lose fat mass or gain lean mass (or both at the same time, which yes, is possible even for elite athletes). Some of these methods can measure a gain of muscle and bone mass. No measure currently is 100% accurate at predicting body fat percentage or true lean mass (this can only be done after death when dissecting and weighing out all the different tissues in your body on a scale!) Every measure of living body composition method has advantages and disadvantages, and no perfect option exists. But what to use and the frequency of use depends on your goals, so hopefully, this helps inform your opinion of the best options for you currently and in the future.
The best time to do any of these measures is first thing in the morning/after waking up, with minimal clothing on after using the toilet, if possible, to reduce water retention or fecal material in the gastrointestinal tract interfering with any measure of body weight or actual “body water.” Many options below will not be accessible as soon as you get out of bed, so consider this effect on estimation error when interpreting your results. The following methods have been chosen and described in order of ease of completion, cost of access, simplicity, and helpfulness in using each measure in your best interest. Use each or all as you see informative.
Methods:
Visual Comparison- many visual guides can help you determine if you are within a healthy body fat range just by the appearance of leanness around your midsection.
Pros:
It's easy: find a location in your house to take a still photo (selfie) of your whole body with as little clothing on as possible as early in the morning as possible (for consistent photo lighting and similar hydration levels) and take a picture of yourself. Track visual changes across weeks to months. Don’t use a mirror, as many mirrors can distort your true image.
Cons:
Might increase body image focus rather than body fat for health focus
Might feel initially uncomfortable showing it to someone else, but other people are the best judges of your current leanness from visual guides.
Bodyweight scale
Pros
The quickest way of knowing you have lost or gained weight (which makes up your fat mass and lean mass)
Frequent daily to weekly measuring is a helpful habit to reduce weight gain. https://pubmed.ncbi.nlm.nih.gov/27113642/ + PMC7311265
Most machines are pretty accurate, given the scale is newish and on flat ground. GIve a 1-3kg difference in measure between different scales.
No skill is required.
Accessible and low cost.
It is useful for assessing gains in lean mass or muscle. If you are completing progressive strength training and your ability to perform with more weight for 8-12 reps of a specific body part exercise and your body weight have been increasing for months, it’s mostly guaranteed that around a third of your new body weight (or more for some lucky people) is due to increased muscle and lean mass in the area of your body you are training. For example, if your hip thrust and squats are progressing in weight during multiple 8-10 rep sets over a couple of months, and you have gained weight using a bodyweight scale, you have likely gained glute muscle mass.
Cons
Interpreting the numbers can initiate a sense of shame or weight stigma. If you plan to lose weight, emphasise celebrating the change amount rather than the total number. If you are 80 kg and have lost 2 kg in the previous month, celebrate the 2 kg loss of inflammatory fat tissue rather than now being 80 kg.
For females with a regular menstrual cycle (17-32 days long), measuring change between months during each set week is more helpful, as fluid retention each week can fluctuate widely between 2 weeks by at least 1-3 kg. For example, if you have a 4-week menstrual cycle, compare week 1 of the first cycle to week 1 of the next cycle and so on, for each week of the cycle to determine body weight change.
A scale does not know the body fat-to-muscle mass ratio or which component is reduced or increased when the scale weight is reduced or increased. Future article will discuss how to know how much muscle versus fat you lose during weight loss after sustained consistent weekly calorie deficit.
A quick note on the body mass index (BMI) ratio (calculate yours here). This ratio was found to give a simple measure of body composition-related health, but we should note the problems with BMI and health prediction BMI calculator (heartfoundation.org.au). A “healthy” range supposedly is between 20 and 25. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents - PubMed (nih.gov). There are better methods to use, though, as the limitations of BMI include:
10-15% of people have excess visceral fat or fat surrounding the internal organs even with a BMI between 20-25 https://pubmed.ncbi.nlm.nih.gov/22625426/
BMI does not measure fat distribution. Visceral fat is more harmful than subcutaneous fat due to the more direct exposure of your organs to inflammatory chemicals of locally stored fat.
It does not reflect the total body fat percentage well (see the large spread in the graphs below). For example, on the graph you can see a male with a BMI around 40 with a bodyfat percentage of around 20% whereas as most have higher bodyfat percentage.
Okay, I have used visual and bodyweight scales to assess my body composition but want more specific numbers for my total fat and muscle mass. The next method is more useful than calculating BMI or following weight gain/loss, as it helps predict visceral fat better than the bodyweight scale.
Bioelectric Impedance Analysis (BIA)
Pros
Easy. All you need to do is stand on a metal stand and hold the device with each hand.
It takes less than 5 minutes to add your details (age, height, goals, and email to send the result to) and complete the scan.
We have a machine at Method Health in the physio room.
Combines body weight and gives you a rough measure of lean and fat mass that is helpful when completed multiple times across a year. https://aspenjournals.onlinelibrary.wiley.com/doi/10.1177/0148607115592672
Cons
Measures, like the body weight scale, are impacted by hydration. This can be reduced by completing the measures as early as possible after waking up with a similar level of water intake before each testing session. So do the measure at the same time of the morning each testing session with as little as known but minimal fluid, food, exercise, or caffeine consumed prior to testing.
Results are also affected by the time of day and external temperature—just be consistent with your testing time.
The BIA-based equation overestimates muscle mass, especially if you are weight-trained. The error range of body fat percentage is also around 10% error. However, this is 90% better than the body weight scale which does not tell you your body fat percentage. Just best not to use this measure to assess small decreases in body fat percentage. Use as a guide a few times per year with your visual guides and body weight scale to measure more frequent changes.
· Note: BIA shouldn’t be used if you have a heart pacemaker, use hearing aids, or are known to be pregnant. If you have a joint replacement or breast implant, completing the measure is safe, but these will be interpreted as fat tissue.
Other Alternatives
DEXA is the gold standard for measuring bone mass (while not as much for muscle mass as body water interferes with the measurement of your muscle), but it is limited in most cities, expensive, and involves low radiation exposure while lying very still for 10 min, which limits how often you should be tested each year. Seek if you are interested in or at risk of bone-related weakness.
Waist circumference is better than BMI for a quick indicator of visceral fat mass which should be low for optimal body composition for health. Aim for less than 80cm for females and 94 cm for males. Here's how to do it yourself How do you measure your waist? (youtube.com) Its cheap as it only requires a flexible tape measure. If you really don’t want to use a body weight scale at home after coaching on how to use it mindfully without self-criticism, waist circumference is a good option. However, 1) it isn't helpful for measuring change when you are already at a low body fat level, 2) only shows large changes (however, large changes are mostly really positive for your health), 3) doesn't predict body fat percentage and 4) doesn’t tell you muscle mass changes.
MRI imaging is the most accurate method of measuring fat and muscle mass without any radiation exposure. Obtaining and interpreting these images, however, involves significant expertise and cost, which are not practical for most. When MRIs (or other technology for digital visual scanning) become more accessible, and cost heaps less, these will be encouraged more often for regular body composition assessment. As a side point, most people are only aware of MRI for medical imaging uses. MRI is often overused for that purpose and, furthermore, can have harmful downstream effects on behavior change, medical utilization cost, and movement confidence. Come talk to Tom the Physio for a best practice health professional opinion about the evidence for useful versus useless medical imaging. Especially if your previous MRI findings have made you move your body less (sometimes unknowingly due to perceived fear and protectiveness) and/or seek injections or surgeries for no or short-term benefit at additional expense.
Bod-pods (gas-based) or underwater weighing (water-based): This involves submersion within a harmless gas pod or submersion in water (with a great exhale prior to submersion), plus the use of equations to predict how your weight differs from how much you displace water (which is different for different levels of leanness). Both methods are hard to access and often cost heaps for a not-very-good error range anyway. Go towards the DEXA method instead.
What about skinfolds? Previously it was popular to use a prediction equation of body fat percentage calculated by measuring a “skin fold” at multiple sites around the body, measured in millimeteres using skin fold calipers. Yes, skinfold assessment is cheap and quick. Still, skinfold estimation equations have an error range of at least 2-3% for fat percentage across all prediction equations, even when the measurement is completed by only a very experienced “skin-folder” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4964757/ Therefore skin folds are really only useful if trying to lose body fat percentage and you don’t want to use visual scales, body weight scales and you have access to an experienced assessor.
This article should finally clarify all you need to measure your body composition for life. Whether it's weight loss, muscle mass gain, or yearly maintenance, mindful use of body weight scales, visual guides, and BIA can help best measure healthy body composition for life, until better technology is invented. Other methods are available but are inaccurate, or costly and less accessible or feasible for daily or weekly use.
Talk to Tom, the physio, or the other Method Health team members for questions and goals around realistic body composition goals and how to use body composition methods yourself to measure your progress or important measures of your health. We understand that body weight and body composition can have a stigma attached to their measurement or inherent embarrassment in regards to previous weight loss attempts. We all understand this and aim as a group to stay health-centered, which strongly emphasizes having a positive body image when communicating with you about your body composition goals. I will write more for Method Health about methods for weight loss and muscle mass gain in the future, so stay tuned!
More resources on body composition for you:
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