In, I made some general comments about body composition as well as discussing some of the possible methods of measuring changes in body composition. These methods included underwater weighing, the scale, tape measures, and calipers.
In the second part of this article, I’d like to discuss some other methods of measuring body composition and make some practical suggestions on how to use the values that measuring body composition is giving you.
Bio-electrical impedance (BIA)
Second to calipers, BIA is probably the most common method of measuring body composition found in most commercial gyms. Although the unit itself can be fairly expensive, BIA has the advantage of being easy to use. Unlike calipers, BIA requires no training to use consistently. Unfortunately, this is about the only advantage of this particular method.
In performing a BIA measurement of body composition, an electrode is typically placed on the hand and foot and then a small, non-dangerous current of electricity is sent from one to the other. The BIA machine measures how long it takes for this current to be conducted and uses that, along with some other data points such as age and sex, to estimate body fat percentage.
The theory of BIA is based on the fact that different components of the body (glycogen, muscle, fat) conduct electricity at different rates, so the speed at which a current travels through the body is roughly indicative of the proportions of each component.
There are two major problems with BIA measurement of body composition. The first is that, for reasons which escape me right now, BIA can’t pick up small changes in body composition. That is, the margin of error on BIA is so large that a few pound difference (which might be critical to a dieting bodybuilder) simply won’t be picked up.
The second problem is that BIA is heavily influenced by hydration state. In that water is a prime conductor of electricity, even small changes in total body hydration state can drastically affect the BIA estimate of body composition. Unless strict hydration protocols are followed (and, let’s face facts, in a gym situation this is going to be
highly unlikely), BIA simply isn’t accurate. For this reason, I don’t recommend the use of BIA (whether expensive commercial units or the home scales) unless there is simply nothing else available.
Infrared reactance (IR)
Another semi-common method of body composition measurement found in commercial gyms is infrared reactance (IR), although it seems to have become less prevalent in recent years. Like BIA above, the benefits of IR is that it is simple to use and requires little training. Also like BIA, that’s about the only good thing that can really be said about it.
IR estimates of body composition is based on the idea that different tissues in the body refract light in different ways. With RI, a light ‘wand’ is placed on the biceps, which then shoots a ray of light into the arm, bouncing it off the upper arm bone, and measuring how much makes it back. This is used to estimate body composition.
As you can imagine, there are a number of problems with this method. The largest is arguably that only fat, muscle and bone in the upper arm is being measured. It represents a huge leap to think that this would necessarily be indicative of the composition of the rest of the body. I can’t even recall a time when I’ve carried significant amounts of fat on my biceps, even when I’ve carried quite a bit on my abdominal skinfold. As with BIA, I don’t recommend the use of IR unless there is simply nothing else available.
There are some other high-tech methods of measuring body composition but most wouldn’t be available to the average trainee for the most part. One of these is DEXA, which stands for Dual-Energy X-ray Absorbitometry. DEXA is an extremely expensive method which can is used in research as it can differentiate the amount of muscle, fat, bone, etc in the body.
Another high-tech method is called the BodPod. Based on the same concept as underwater weighing (see part 1), the BodPod measures how much air is displaced by an individual and uses that to estimate body composition. The last time I looked, one of these machines cost about $70,000 so I doubt you’ll see one at the local World Gym any time soon.
A brief caveat: the mirror
Before getting into some details of how readers can use body composition measurements, I want to discuss one topic. A sentiment made frequently by bodybuilders is that they don’t believe in body composition measurements (or even tape measure measurements) because they are judged on appearance, not on the scale. There is much truth to this: the judges couldn’t care less if you’re 4% bodyfat if it means that you lost a lot of size and symmetry to get there. The individuals who express this sentiment frequently recommend simply using the mirror to judge how well (or poorly) a diet or training program is going.
Now, I have no problem with mirror for advanced bodybuilders or fitness competitors. At that level, most can tell by looking in the mirror whether their diet is working or not, and can make quick adjustments that way.
However, I don’t think that most individuals have the necessary skills (or the ability to be honest to themselves) to use only the mirror. It’s simply too easy to see what you want to see (and let’s face it, we all know which mirror in our house or at the gym makes us look just a little bit leaner than the others) and get into trouble because of it. The fat blinders tend to come on during the massing cycle and while the mirror can lie, calipers can’t. If you’re getting fat, the caliper measurements will go up, simple as that.
Using the numbers
Ok, with that said, let’s talk about how you can use body composition measurements to tweak your training and diet for optimal gains. I’ll assume at this point you’ve made some decision as to what method to use and we’ll go from there. To reiterate something I said in part 1, I personally feel that consistency is more important than accuracy and we’re going to use that in the following calculations that I’m going to present.
How often to measure
A question that frequently comes up with regards to body composition is how often to take measurements. I think the answer to how often depends on the individual and what they are trying to accomplish. That is, for a bodybuilder in a mass phase, I don’t think that weekly body composition measurements will be terribly illuminating, due to the generally slow rate of muscle gain. Once every 2-4 weeks would probably be more than enough. However, for a bodybuilder in the final weeks of pre-contest prep, measuring body composition weekly might be necessary to make adjustments quickly if the diet isn’t working (i.e. if the fat isn’t coming off quickly enough, you’ll have to cut calories a bit more or add in more cardio). For the average dieter, measuring body composition every 2-4 weeks is probably sufficient. It’s quite easy to become obsessive about measuring body composition (I should know, I’ve been there) and start freaking out when changes aren’t coming week to week. Considering that fat loss tends to be non-linear, measuring every week is just asking for frustration.
An example lifter
Ok, let’s dream up a hypothetical bodybuilder who is 200 lbs and 10% bodyfat. As per the calculations done in part 1, this means he has 20 lbs of fat and 180 lbs of lean body mass. We’ll use him in all of the examples to come.
Let’s say that our bodybuilder decides that he wants to get bigger. So he moves into a mass training program with calories set 10% above maintenance (about 3300 calories/day or so assuming an estimated maintenance level of 3000 calories). Over a month, let’s say he gains 3 lbs and his bodyfat percentage goes up to 10.3%. He now has
203 lbs * 10.3% = 21 lbs fat
203 – 21 = 182 lbs of lean body mass
That tells us that over that month he gained 2 lbs of muscle and only 1 lb of fat. Now, to see if he can gain muscle any faster, he increases calories by another 10% per day (to 3600 calories/day), gaining 4 lbs in the next month. Bodyfat goes up to 11%. He now has:
207 lbs * 11% = 23 lbs fat
207 – 23 = 184 lbs of lean body mass
So by adding another 300 cal/day to his diet, he still only gained 2 lbs of muscle but gained an additional pound of fat. This would tell our bodybuilder that raising calories much more than 10% above maintenance only results in greater fat gains (i.e. that he’s not gonna gain more than 2 lbs. of muscle/month no matter how high calories go). Our bodybuilder might also experiment with consuming only 150 calories/day over maintenance to see what happens. He might find that while he gains no fat, he only gains 1/2 lb of muscle. Then he’d have to make a choice over gaining muscle appreciably faster (2 lbs/month vs. 1/2 lb/month) but also gaining more bodyfat (1 lb/month vs. no gain).
Over a few months of such record keeping, our bodybuilder will have an excellent idea of his optimal caloric intake to maximize muscle gains and minimize fat gains. He could also use this approach to test new supplements, types of training, or dietary approaches (i.e. instead of the baseline diet I presented, trying the Zone/Isocaloric diet for mass gains, or more calories on training days and less on non-training days). That is, after establishing a baseline of 2 lbs/month, he could add supplement X and see if muscle gains are noticeably faster (say 3 lbs/month).
Now, it’s time for our bodybuilder to diet down and, once again, he wants to optimize caloric intake to maximize fat loss while minimizing muscle loss. The same strategy as above would be used, simply in reverse. So from a baseline of 3000 calories/day, our bodybuilder would subtract 300 cal/day (and/or add aerobics) and measure body composition after 2-4 weeks. After establishing baseline fat loss, calories could be decreased a little bit more (or aerobics increased) to see if fat loss is noticeably increased (or muscle loss is increased). This strategy could also be used to test out various fat loss supplements such as the ECA stack, Adipokinetix, etc. to see if they are noticeably increasing fat loss beyond baseline.
Summary and conclusions
Measuring body composition is one method that bodybuilders and even recreational lifters can track the progress (or lack thereof) of their training and dietary programs. There are a number of different ways to measure body composition including underwater weighing, the scale, calipers, a tape measure, bioelectrical impedance, and infrared reactance.
For the most part, I think that a combination of the scale, calipers and a tape measure will provide the best set of numbers for most trainees. Advanced bodybuilders or fitness competitors may wish to rely more on the mirror to track changes, but this requires that an individual be very honest with themselves (or have a very honest coach).
Semi-regular body composition measurements taken every 2-4 weeks can be used to estimate the changes which are occurring from your training program. They can be used to dial in caloric intake and optimal training as well as to test the usefulness of various supplements. Modifications to training and diet can be made based on the estimates until a lifter has zeroed in on what’s optimal for his body in terms of diet, training, supplements, etc.