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Measuring and Tracking Body Composition

Continuing from the last blog, let's look at some of the practical aspects involved in both measuring and tracking changes in body composition or body fat percentage (BF%). I will be discussing a number of methods but it's important to realize that none provide more than an estimate. Every method has pros and cons.

From a tracking standpoint, changes are more important than absolute numbers. Since they can also be relevant, I will also be looking at some non-body composition methods of tracking progress in this blog and will make recommendations for combinations of those methods that can be used.

True Body Composition Measurements

The first set of methods I want to discuss are true body composition measurements in that they measure (or estimate) some aspect of actual body composition. They vary in their accuracy, difficulty of use and availability and I will describe them more or less in order from least to most complex.

Body-Mass Index (BMI)

The BMI is a fairly old measurement which relates an individual's body weight to their height. More technically BMI is defined as weight in kilograms divided by height in meters squared. For decades BMI has been used to indicate general health or some kind of ideal weight and insurance companies use some version of it to determine how much to charge you per month.

A high BMI tends to correlate with health risk and a BMI greater than 25 kg/m2 is defined as overweight and a BMI greater than 30 kg/m2 is considered obese. Very low values are equally problematic with a value below 18.5 kg/m2 is considered unhealthy or malnourished (possibly indicating an eating disorder or wasting disease). Between 18.5 and 25 is considered optimal. It's critical to note that these are only averages and it's been established that individuals with a high BMI can be healthy while those in the optimal range may be unhealthy.

Part of the reason for this is that BMI is not strictly speaking a measurement of BF% and doesn't indicate body composition or how much fat or LBM someone is carrying. Two females who are 5'7" tall and who weigh 150 pounds have the same BMI. If one is an athlete with 20% body fat and the other is inactive at 35% body fat, not only is their body composition different but so are their relatively health risks. It's also not uncommon for active individuals, generally males, to be told that they are overweight due to a high BMI score although they are relatively lean and simply carry more muscle mass. This leads to active individuals to often suggest that BMI should be thrown out for being useless but this is an over reaction. BMI was never meant to be used in an athletic population.

In the general public, it is simply not that common to find people with high BMI who also have a low BF% although people with a low BMI often have a fairly high BF% (they are often called skinny fat). It's also possible to have a high BMI and be metabolically healthy or a low BMI and be unhealthy. But no body composition method is perfect and BMI is not useless, its limitations simply have to be acknowledged. For that same group, BMI will give at least a rough indicator of general health risk along with giving a fairly easy way to track changes from diet and exercise (technically since height is not changing, tracking body weight would provide the same information).

And while BMI has primarily been used to track overall health trends, it turns out that it can give a rough estimate of BF%. A calculator to determine BMI can be found here:

That BMI value can be used to estimate BF% here:

While the above links may be inappropriate for athletic individuals, I think it is probably the easiest approach for people first starting out. It's quick and easy, provides a good starting point and can be used to track changes over time. Once someone has been working out consistently for 6+ months, I would not consider BMI to be accurate and they should use another of the described methods.

Tape Measure/Circumference Measurements

Although decidedly low-tech, it is actually possible to get a decent estimate of BF% with nothing more than a tape measure. The military has often developed a lot of these equations since they need to be able to measure a lot of people quickly and easily. There are online calculators that estimate BF% in this fashion that generate results that are at least similar to more complicated methods which can be found here:

Even if they are not used to track body composition per se, tape measure measurements still provide another way to track general progress while dieting (or attempting to gain muscle). During a diet, a decrease in circumference measures (i.e. diameter of the hips or arms) generally indicates body fat loss and it's not uncommon to see this occur even in the absence of much weight loss. Muscle is denser and takes up less space than body fat so someone gaining some muscle while losing fat should still see a reduction in their tape measure measurements. Taking a variety of measurements including arms, bust, waist, abdomen, hip and thighs can provide a general indication of whether fat is being lost and specifically from where. Even a single trouble spot (i.e. arms or thighs) could be tracked in this fashion.

Whether used for BF% estimation or just as a general tracking method, the tape measure is not without problems. First and foremost it's critical to always measure at the same spot, around the largest part of the bust or halfway down the thigh or what have you or the values can't be compared to each other. This is not always easy and even slight differences in where the measurement is taken can make them inaccurate. It's also important to at least try to pull the tape measure to the same tension every time, neither too tight nor too loose. This can also be very difficult to do and there are tape measures with a spring on the end such as the Gulick II which will improve the accuracy of measurements.

Waist/Hip Ratio (WHR)

The waist/hip ratio is exactly what it sounds like, that is the ratio of the waist (measured with a tape measure at the narrowest part) and the hips (measured with a tape measure at the widest part). Technically the WHR ratio is not a measure of body composition but a measure of body fat distribution and health risk. On average, women tend to have a lower WHR than men but WHR can go up with menopause, PCOS/subclinical hyperandrogenism and in obesity. A WHR calculator can be found here:

As with circumference measures, it's important to not overtighten the tape measure.

Skinfold Calipers

Possibly the most commonly used method of BF% measurement are skinfold calipers, a small plastic device that is used to squeeze fat at different parts of the body. The measurements go into an equation that then estimates BF%. A variety of sites ranging from 3 to 7 (or more) can be used and numerous different equations exist. Typical sites for women's measurement are the back of the arm, chest, iliac crest (above the hip) and thigh. Calipers give a BF% estimate that is usually close to much more high-tech methods at least in the hands of a trained user. Trained is a key word here as using calipers correctly takes a good deal of practice and many do not have it (this can be a big problem at commercial gyms with a high employee turnover). My general experience is that most trainers are hesitant to grab as much fat as they should. Many women have a thigh skinfold that is nearly impossible to measure accurately in many cases. This can lead to drastically underestimated BF% values.

While generally accurate when used properly, calipers do have an inherent error of about 2-3% in either direction (note that all methods have some degree of inherent error). This means that they may not be able to pick up smaller changes in BF% to begin with. Fat cells do store water and changes in water retention (that will usually show up as changes in scale weight) can impact on skinfold measurement. The equations can be problematic as well. A host of assumptions are being made about bone density (which differs between women and men, can vary with training, etc.) which can cause them to give some strange values, even if the skinfold measurements are accurate. The equations will occasionally put women well below the 10% lower limit for essential fat, men have been estimated at 1-2% and, due to differences in bone density, black male athletes are occasionally given a negative number. Although it doesn't give an estimate of BF%, some recommend just tracking the skinfold changes. If the thigh skinfold goes down from 25mm to 22mm, fat has been lost.

Other Tracking Methods

While having some initial estimate of BF% is important to track on some level, there are other methods of tracking progress on a diet (or when trying to gain muscle). None estimate body composition per se but in conjunction with one of the methods above, they have their use. Tape measure measurements are one of these.

The Scale

Hopefully after reading the last blog, you understand that short-term fluctuations in scale weight don't represent anything real (in terms of the gain or loss of actual body fat or LBM). I should mention one major exception. For women who are carrying a significant amount of body fat, assuming even the most basic exercise and nutrition program is in place, almost all weight lost will be body fat outside of the initial drop in water weight. In this case, the scale may be all that is necessary to track progress.

This is especially true as many of the true BF% methods tend to become inaccurate at the extremes of high or low body fat. For women not in this situation, the scale can still provide useful information but only if the person using it can accept that day-to-day changes are meaningless and they should not make poor lifestyle choices based on those changes.

In recent years, there has been a good bit of backlash against the scale, especially for women. Some of this is based on what I've discussed already in terms of it not representing changes in body composition or what have you, that the day-to-day changes make the practice useless. While I have made similar arguments above, the key to weighing is to do it daily and use those measurements to create a 7-day rolling average (this just means that every new day's number will replace the value from 7 days ago). This approach smoothes out the daily fluctuations (one higher day is offset by a lower day) and creates a trend line that is either flat, downwards or upwards representing no change or a real loss or gain of some type of body tissue (the scale still can't say if it's fat or muscle). It also eliminates the inaccuracy of measuring once weekly where a single day's fluctuation can give a very inaccurate picture of what is actually occurring in the body.

Recent research has found that daily weighing actually helps people to adopt new health habits, probably by focusing their attention to those goals. If a woman weighs daily, it acts as an immediate reminder that she is attempting to change her eating or activity habits and that along helps with adherence. Regular monitoring of body weight has also been shown to help with long-term weight maintenance. While short-term fluctuations should still be ignored, a true increase in weight of perhaps 3-5 pounds should indicate that the dieter is backsliding and that more focus needs to be placed on eating and activity patterns. Regarding psychological stress, while some women might be impacted, overall the practice of daily weighing has not been shown to cause psychological problems.

Whether dieting or attempting to gain weight, it is ideal to weigh at the same time of day under the same conditions. This usually means in the morning, preferably after using the bathroom. Weight can be taken naked or clothed although naked will give more consistent values (clothes can weigh 1-2 lbs or 0.5-1 kg or so). Clearly if any given woman finds that daily weighing is causing her psychological stress, it should be abandoned. But overall, so long as the scale is used properly, it is a useful tool with daily weighing being the superior approach overall. I would mention that even this approach to using the scale can be a problem for the normally cycling woman as the weekly changes in body weight will make the averages inaccurate. I will discuss this issue below along with how to take it into account/work around it.

The Mirror/Pictures

Along with the tape measure and the scale, another non-body composition method that can be useful to track changes is to simply use the mirror or pictures. The reality is that most people (women or men) who want to lose weight/fat or change body composition do it primarily to look better (specifically to look better naked). The mirror or pictures can be useful in this regard but there are some issues that I want to address.

One problem is that the mirror or pictures can lie. Or, perhaps more accurately, the person's brain can lie to them about what they are seeing. This is most pronounced in many eating disorders where an extremely skinny individual will still "see" a fat person in the mirror (males tend to see a skinny body even while heavily muscled). Even outside of that extreme, most people will tend to focus on what they perceive as their specific trouble spots or simply see a different body that is actually there. It's extremely common for dieters who have reached an extremely low level of body fat to see themselves as fat even when they are at a BF% that is fairly low.

There is an additional issue which is that there are often differences in mirrors or lighting that can impact drastically on a person's visual appearance. In general, very bright lights tend to worsen appearance as it washes everything out and slightly darker lights (within limits) improve it. Every gym seems to have one particularly magic mirror that makes people look significantly leaner or more muscular than they actually are. Using the same mirror under the same lighting will avoid this problem.

Similar to the mirror, pictures can provide not only a way of tracking but a record of the changes that have occurred. In some ways, they may be better than the mirror in that they are taken less frequently. Over short periods of time, unless someone is extremely lean (here I am talking about certain types of athletes), visual changes just don't occur that quickly. Looking in the mirror daily, someone is highly unlikely to see any visual changes occurring and this can be demoralising. Even if those changes are occurring, they tend to be too small on a day-to-day basis to be noticeable. In contrast, taking pictures every 4-8 weeks will tend to show more visual changes, especially if they are compared side by side.

As with all aspects of tracking changes, it's critical to take pictures under the same conditions. This means that the same clothing (or something very similar should be worn), the same lighting, distance from the camera, etc. should be used. If this is not done, the pictures will not be comparable to one another. It's a dirty little secret in the fitness and diet industry that many of the before and after pictures being used to sell a product may be taken on the same day. Changing the lighting from harsh to lowered, tanning, having the person wear a more flattering outfit, change their posture, go from frowning to smiling makes a staggering difference in no time at all. If you look closely the person may be standing slightly differently, twisted at the waist to narrow it, etc.

Clothing Fit

Similar to the use of the tape measure and circumference measurements, another approach to tracking progress is to go by the way clothes fit. In some ways this is actually superior to the tape measure in that the issue of measuring the exact same place is eliminated. If a specific piece of clothing is fitting more loosely, body composition is improving and if that same piece of clothing is fitting more tightly, it may be worsening. I say may as those athletes focusing on gaining muscle may still find some clothes fitting more tightly due to the increases in muscle mass. Even after the dieting is done, when long-term maintenance is the goal, clothing be used to catch problems before they get out of hand (this is just another method of monitoring like using the scale). If a specific piece of clothing starts to get tight again, weight regain may be occurring and the individual will know to become more focused on their eating and exercise habits.

Choosing From the Different Methods

Having looked at a variety of ways of either estimating BF% or tracking progress while attempting to alter body composition (whether losing fat or gaining muscle) I want to make some more specific recommendations about how to integrate them. Once again, every method has its pros and cons, benefits and drawbacks. None are perfect and most are best used to track progress over time rather than being considered as a one-time measurement. Regardless of the specific measurement, if it is changing in the goal direction (i.e. down for fat loss, up for muscle gain), that is what matters most.

Perhaps the best way to offset any given method's cons is to use some combination of methods rather than relying exclusively on one (perhaps the lone exception to this is the woman carrying significant fat for whom weight loss will almost always indicate fat loss). That way, any changes that are not picked up by one method will become apparent by another. So consider a woman who we know lost 2% body fat at (roughly 2.5 lbs/1.2 kg for a 130 lb/59 kg woman). The error inherent in calipers might not be able to measure that but a 7-day rolling average of her scale weight certainly would. If she were very lean, she might also notice visual changes in the mirror.

I think you get the idea.

Again, a 7-day average or at least measuring at specific times of the month along with ignoring small daily variations are the key to making this method useful. Used properly, calipers are surprisingly accurate but tend to have problems at the high and low extremes of body fat. Paying attention only to changes in the values can be useful here although this doesn't provide a BF% estimate. As well, without a helper, only a handful of sites can be measured unless someone is a contortionist. BMI is quick and easy and can either be used as a general indicator of health or to estimate BF%.

Tracking the WHR ratio may be useful for women who are carrying large amounts of fat around the midsection since it indicates the loss of visceral fat which indicates an improvement in health. The tape measure can be surprisingly accurate to estimate BF% as well as tracking changes in inches overall.

To one or more of those methods that tracks or semi-tracks some aspect of body composition, the mirror or pictures (or a test piece of clothing) can be added. Basically the combination of a BF% estimate, possibly another method that tracks regional changes in body composition (WHR or tape measure) and at least one non-BF% method of tracking progress will probably give the best combination in terms of providing enough different data points to truly track changes. Some may not even need all of those and I can't cover every possible circumstance to make recommendations. I'd only reiterate, at the risk of beating a dead horse, is that short-term changes in any of these measurement methods tend to mean very little in the big scheme. Focusing on larger changes is the key to making any of them work.

Let me finish by making an often underappreciated point which is that changes in body composition or even weight are generally not only slow but rarely happen in a constant or linear fashion. Weight or BF % may drop, then remain unchanged for a week or two before dropping significantly (seemingly overnight), etc. The same tends to occur for those trying to gain weight with weight going up, stalling, going up some more. There are a number of reasons for these plateaus, women must understand that a lack of change for a week or two means nothing as long as they are sticking to their goals/plans.

Body Composition Numbers

Having looked at the concept of body composition/BF% in the last blog and methods of estimating/tracking it above, I want to address the question of what a good or appropriate BF% might be. The answer to that question depends entirely on the situation. The optimal BF% for basic health will differ than that for optimal athletic or appearance goals. While healthy levels BF% have been thrown around, it's now becoming clear that it is possible to be healthy while carrying significant body fat or to be unhealthy while being lean. Much of this comes down to activity levels and active individuals with more fat are often more metabolically healthy than those who are lean but inactive. Which isn't to say that there isn't a general relationship between increasing BF% levels and health, simply that it is not universal.

While excess body fat tend to be highly associated with health risks, it's equally possible to carry too little body fat for optimal health. At the lower extremes of BF% (10-12% for women) as seen among some athletes or in anorexia, a woman's physiology is severely negatively impacted in terms of her hormone levels, menstrual cycle function, etc. This will be discussed in great detail in later blogs. This just means that there is some happy medium to be had between too little and too much in terms of health status. I would mention that, even in those cases where a woman might not be able to achieve a supposed "healthy" BF%, even a 5-10% fat loss from her current level drastically improves health and fertility.

In the general public, the types of bodies that are often held up as societal ideals are perhaps 18-20% for women or a bit higher, generally with less muscularity. To put this into perspective, women tend to get visible abdominal muscles (the 6-pack) around 15-17% or so and this is leaner than many want to be outside of specific athletic subcultures. While many skinny and/or light women might appear lean, they often have a high BF% which is called being-skinny fat.

In the next blog we will look at diet categories.

Coach HB

The above information is taken from the The Woman's Book by Lyle Mcdonald with Eric Elms.

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