Body Composition: Which Numbers Matter?

Over the years, my perspective on numbers and their value has changed with respect to health and the body. Before I knew much about exercise science or even heard of the words “body composition,” the only thing I knew about was weight. And that word was “scary.” Like many females, I avoided the scale at all costs. I went by the feel of my clothes, and I didn’t want to know any numbers (not that this is bad, trusting your clothes, but the intense fear of a number isn’t great). It was like a warning alarm would sound off if I stepped on to the scale. 

I don’t know where this fear came from or why I let it dictate my perception of my health and myself. As time went on, and I pursued education in health and exercise science, I began to learn how these numbers related to body composition. I also realized that weight is pretty much as useful as my mom having an iPhone. (She has a Galaxy and giving her my phone is like handing her a foreign object she has no idea what to do with it.) My point is this: Weight is just gravitational pull on the body, mass times gravity. What does this number really tell you about your body? As it turns out, not much. You have to know the make up of the weight for it to be helpful. 

Unfortunately, accurately measuring body composition is difficult and expensive. Although there are numerous, extensive definitions of body composition, it is basically the amount of fat mass vs. lean mass. Body composition is typically reported in a percentage of fat mass. Therefore, just stepping on a scale to attain a weight will not shed any insight into how much weight is lean body mass and how much weight is fat mass. Methods that provide fairly accurate body-composition analysis include the Dual X-ray Energy Absorptiometry (DEXA), Bod Pod and hydrostatic weighing. Typically, these machines are located at exercise science laboratories and hospitals and are fairly expensive. 

Fortunately, there are economically friendly tools for measuring body composition, such as skin folds and bioelectrical impedance analysis (BIA). Skin-fold calipers measure body fat by pinching visceral fat at specific anatomic locations, and those numbers are used in a formula to estimate total body-fat percentage. Unfortunately, it can be challenge to measure at the exact anatomical site, which can make the measurement less accurate. A downside to this is accuracy on selecting the position of the site. To help improve the validity of the measurements, three measurements are taken at each site and averaged to obtain a more accurate number. 

Bioelectrical impedance sends an electrical current through the body to determine body composition. Because lean mass contains more water, it takes the electrical current less time to travel through the body and assess composition. BIA is typically assessed through hand-held devices or scales. The accuracy of this measurement can be compromised by the individual’s hydration level, with dehydration causing an overestimation of body composition, and overhydration having the reverse effect. 

Unfortunately, not many of these measurements are conducted in clinical settings, so weight and body mass index (BMI) tend to be the default measurements. BMI is a measure of mass divided by height squared. This number can provide insight into a person’s general well-being in regards to weight; however, it still does not offer a true representation of a person’s body composition. 

Waist-to-hip ratio is another common measurement and is an efficient and effective tool for assessing health. Waist-to-hip ratio measures the circumference of the waist at the smallest point and compares it to the circumference of the hips at the widest point. The higher ratio indicates greater adipose tissue exists around the abdominal region, which can signal a greater risk for metabolic syndrome and associated illnesses. 

If you have access to finding out your true body composition by hydrostatic weighing, a DEXA or BodPod—go for it. If not, some of the other methods discussed earlier will work, but they may offer a less accurate picture of your true body composition. However, if you experience improvements in these numbers over time, you can feel confident that you are making progress in improving your health.  

Finally, guard against becoming obsessed with your weight. This number does not define you, nor does it say a whole lot about your health or your body composition.

Source : By Kelley Vargo / Ace