Charting Progress on the Baseline Diet, Part 1

by Lyle McDonald, CSCS
Author of The Ketogenic Diet

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Introduction

In my last two articles, I talked about how to set up a baseline diet for basic bodybuilding purposes. In this article, I would like to talk about how an individual might monitor how well (or poorly) that diet is working for them in order to determine if a change is necessary. There are a number of methods to monitor progress and changes in response to a diet or training program, ranging from low-tech to high-tech and poor-quality to high-quality.

Bodyweight vs. Bodyfat

One distinction that must be made by all trainees (whether bodybuilders or dieters) is that of bodyweight versus bodyfat. In general, dieters tend to fixate on changes in bodyweight as the only measure of success or failure of the diet. Better informed dieters (and most bodybuilders) know that changes in body composition are the better measure of whether a diet or training approach is working. So what's the difference?

Bodyweight refers to your total weight, including muscle, bone, your internal organs, bodyfat, water, glycogen, minerals, hair, etc. Bodyfat refers only to the fat carried on your body (technically we should distinguish between essential bodyfat, which surrounds the organs and is essential for life, and subcutaneous bodyfat which is the stuff carried under your skin that we want to get rid of).

Changes in bodyweight (typically measured by a scale) don't give you any information about what is being gained or lost. A loss of 10 lbs. might represent 10 lbs. of fat loss (good), 10 lbs. of water loss (neither here nor there), or 10 lbs. of muscle loss (bad). Therefore, dieters/bodybuilders need to get into the habit of tracking changes in body composition.

Models of body composition

As described above, the body is made up of a number of different tissues (muscle, bone, etc). To simplify the study of body composition, a variety of models have been developed. The simplest of these is the 2-component model which divides the body into two components: fat mass and lean body mass (LBM, everything that isn't fat) Although there are far more complicated models available (including some 4 component models) which subdivide the body further, they are unnecessary for the point of this article. Pick up an exercise physiology book if you're really that interested.

Anyway, by dividing the body into a number of different components, we can define an important term which is bodyfat percentage.

BF% = total lbs. fat/ total body weight

As well,

LBM = total bodyweight - total lbs. fat

So if someone has 20 lbs. of fat and weighs 200 lbs., they have

BF% = 20/200 = 10%

LBM = 200 - 20 = 180 lbs.

So this person has 20 lbs. of bodyfat, 180 lbs. of LBM and 10% bodyfat.

As well, by subdividing the body into various components it becomes possible to track changes in body fat mass and LBM through any number of methods. Now, one problem with all of the currently available methods (well, the ones that would be available outside of a research laboratory) is that none are perfect. All have to make certain assumptions about the body (including such factors as uniform skin thickness, bone density, fat deposition patterns) that may or may not be correct for a given individual. In fact, current research is showing that most of the assumptions upon which these methods are based are all turning out to be more or less incorrect.

Accuracy vs. Consistency

Now, does the above mean that none of these methods are useful? Of course not. Since we're not doing clinical body composition measurement, a small sacrifice in absolute accuracy can be made as long as consistency can be maintained. Since some readers may not understand the distinction, I'll try to explain briefly. Accuracy refers to how close to a true value a given measurement is. That is, let's say that we could dissect you right now (and put you back together) and it turned out that your bodyfat percentage was 10%. Then let's say we used some other method of measuring bodyfat and it also said your bodyfat percentage was 10%. It would be said to have a high degree of accuracy. If that same method said your bodyfat was actually 20%, it would have a low degree of accuracy.

Consistency describes a situation where a given method of measurement may not be accurate, but is consistently not accurate. That is, say we dissect you twice and measure you with some body composition method twice and get the following results:

Although the other method was inaccurate (overestimating by 10%) is consistent in that it reflected the same 2% loss. So both methods (one accurate, one not accurate) are consistent in that they both show the same loss (or gain) over a given time period. Overall, I prefer individuals to become more concerned with consistency (measuring themselves with the same method under the identical conditions) than with accuracy.

Methods for measuring body composition

Ok, enough introductory ramblings, let's talk about some of the most common methods for measuring body composition.

The scale

As mentioned above, the scale is arguably over utilized by most dieters (and I imagine by some bodybuilders) to track progress. As also mentioned above, it has some serious shortcomings, especially if used by itself, in tracking progress since it does not indicate what (muscle, fat, water, bone) is being lost or gained. Overall I would prefer folks not use a scale unless it is with another method described below.

The tape measure

A tape measure can readily be used for a number of applications in tracking progress/measuring body composition. First and foremost, there are any number of equations available which estimate body fat percentage based on various girth measures (such as hips, waist, wrist, etc). Unfortunately, these tend not to be terribly accurate because the tape measure can't differentiate between someone who has a wide muscular waist and someone who has a wide fat waist. As well, someone with a very wide hip structure (because of the way their skeleton is built) will have body composition overestimated by any equation that uses hip girth. Overall I don't generally recommend the use of girth equations to estimate bodyfat percentage.

A second application for a tape measure (especially for bodybuilders) is to track changes in limb girth. That is, if a bodybuilder wanted to see if his new super-duper arm training program was working or not, he could measure arm girth (flexed, relaxed or both) at the beginning of the program and again at the end and see if it did actually put 1/2" on his arms. The problem here, again, is that the tape measure can't strictly differentiate between the gain (or loss) of fat versus muscle. It's conceivable the 1/2" gain on the arms during an arm training program (coupled with a high calorie diet) might just be fat gain. A potential solution appears below.

Underwater weighing

Underwater weighing (also called hydrostatic weighing) is considered the 'gold standard' of body composition methods. Based on the simple premise that different tissues have different levels of buoyancy (i.e. fat floats, muscle and bone don't) by comparing the weight of someone on land to their weight underwater, you can determine body fat percentage.

Like all methods, though, underwater weighing has some methodology problems. First and foremost, it makes some assumptions about the density of various tissues (bone, muscle, fat) which tend to vary by population (i.e. African-Americans tend to have denser bones, Asians tend to have less dense bones, Caucasians are right in the middle). As well, the assumptions about bone density can be affected if an individual has been engaged in a high-intensity weight training program, as that is known to increase bone density.

As well, underwater weighing requires the subject to exhale all the air from their lungs and then dunk their head under the water to be weighed. I don't know about you, but breathing out all my air and then going underwater isn't something I'm sure I would find enjoyable. Because of this, many individuals will not breath out completely and this is compounded by the fact that there is always a small amount of air left in the lungs that can't be gotten rid of. Researchers have to make adjustments (some would call this a fudge factor) for this.

Finally, outside of exercise physiology/human performance labs, there aren't a lot of underwater weighing tanks to be found. And when they are, a small fee is usually charged by the operator. So while underwater weighing may be the gold standard, it is not really that practical for most individuals to use on a regular basis.

Skinfold calipers

Calipers are small devices (plastic or metal) used to measure the thickness of skin/fat folds. After the scale, calipers are probably the second most common method used (especially in health clubs) to track progress. Caliper measurements of bodyfat are based on the fact that the majority of fat in the body is held underneath the skin (called subcutaneous fat). Since the fat sits on top of muscle as a separate layer, it can be raised away and measured with the calipers. A variety of equations have been developed to convert caliper measurements into bodyfat percentage (technically speaking, caliper measurements give you an indication of body density, which goes into another equation to give bodyfat percentage). These equations are typically derived by underwater weighing someone and then caliper measuring them and working out an equation to fit the data.

Caliper equations use anywhere from 3 to 7 sites (and some use up to 11) to estimate bodyfat. Typical sites are chest, abdominal, iliac crest (above the hipbone), thigh, triceps, axilla (in the armpit), subscapula (underneath the shoulder blade). Some researchers have also used biceps, medial calf and even cheek. The most common equation is probably the Jackson-Pollock 3-site which uses chest, abdominal, and thigh for men (since these are arguably the places most men carry their bodyfat) and triceps, ilium, and thigh for women (since these are arguably the places most women carry their bodyfat). There are also a number of population specific equations that have been developed.

A problem with these equations is that individuals who show unusual bodyfat patterns (for example a female that carries a lot of fat on her abdominals or a man who carries a lot in his lower back) will tend to be underestimated if only 3 sites are used. The partial solution, which is to use more site measurements, is confounded by the fact that it gives the person doing the measuring more chances to make a mistake.

As well, it should be noted that calipers do take a good deal of practice to use consistently (or accurately). I've typically read that someone must measure at least 100 people to be even reasonably competent in using calipers. Additionally, most people have slightly different methods of using calipers (in terms of how hard they pull, where exactly they raise the skinfold). Considering the generally high turnover rate at most gyms, this makes it hard to get even a consistent measurement (because two individuals who measure you may be 2% off because of different technique). For this reason I usually suggest that individuals buy their own calipers (see part II of this article for recommendations) and learn to take their own caliper measurements. This allows an individuals to take their own measurements whenever they want (for example I typically measure myself every few weeks first thing on Monday morning) and they can be assured of consistency since they are the person taking the measurement.

Calipers plus the tape measure: a winning combination

Perhaps one of the best ideas I've seen for tracking changes is to use a combination of calipers and the tape measure. Let's return to our bodybuilder trying to make his arms bigger. If he were to measure triceps and biceps skinfold (with calipers) as well as girth (with the tape measure) he would be able to determine whether the 1/2" gain in arm size was muscle or fat. If there were no change in caliper measurement with a 1/2" increase in girth, he could conclude that the gains were in muscle mass in that area. If the caliper measurements did increase, he could conclude that some of the gain was fat and some was muscle (there's no easy way to find out how much of each was gained). This gives far more objective data than just using one or the other by itself.

Next time: a discussion of several other popular methods of body composition measurement and some practical suggestions.