If you're curious what it's like to have your body fat professionally measured, I'll tell you about my experience. I just had it done.
I've measured or estimated my body fat through several methods over the years, at various points from obese to athletically fit. To me it's a matter of scientific interest. I'd be equally curious just what bacteria live in my dental plaque, and for much the same reasons. I didn't choose to put it there and I want to know how to get rid of it! At the same time, I don't judge myself, because at this moment, my body is what it is. I want an accurate read. I want to know where I stand for longevity reasons, for Alzheimer's prevention reasons, and for athletic performance reasons. Others might care more about other factors, such as knee pain, sleep apnea, or heart disease. Whatever works.
What have I tried? In chronological order:
I've tried using a measuring tape and calculating my waist-to-hip ratio. (W/H).
I've tried the BMI chart.
I've used a hand-held body fat monitor that works through bioelectrical impedance. (Omron)
I've used a scale with bioelectrical impedance. (Weight Watchers)
I've used a body fat caliper to do the pinch test.
All these methods gave me similar results. I don't particularly endorse or dispute any of them. I can say that I had some issues with data collection; all of these things are easier with the help of a second set of hands. I had to mail-order the calipers because I couldn't find them for sale anywhere. The impedance monitor can be gamed by drinking extra water at your starting measurement and then being dehydrated at your ending measurement. The scale doesn't let you reset your age. The waist-to-hip measurements can be tricky to find. Where is my natural hip exactly? I didn't particularly have a waist at the time. The very concept of BMI tends to make Americans apoplectic, but look. It's endorsed by the CDC, the Mayo Clinic, and the Harvard School of Health, and that's good enough for me. I have no reason to dispute their findings and I have no more authoritative sources. I'm out for my own personal optimal health results, not a scientific debate for which I have no credentials. Also, I'm not defensive about my body image or my state of health.
Back to the professional body fat test.
My new personal trainer at the gym sprung it on me. First he had me weigh in, which is fine. I hit 123 pounds in clothes and shoes. (I'm 5'4" for reference). It was afternoon, and I'd already eaten and hydrated. I'm more interested in what I weigh for the majority of each day, not that fraction of a second first thing in the morning when my stomach is empty. I have nothing to worry about. Thirty-five pounds ago, maybe. Now, I'm in the healthy range for my height, as I have been for the past two years.
Next, he got out the calipers. They're like the pair I bought, only bigger. The major difference was that he took four measurements, three of which I couldn't have taken by myself. The instructions with my calipers said to pinch some fat an inch from the point of the pelvic bone, the area I used to refer to affectionately as my jelly roll. My trainer took two measurements on my upper arm, one on my back near my shoulder blade, and one on my side above my ribs. He took notes, and I could see that the form leaves room for future entries. The plan is to repeat the measurements once a month.
I laughed while he was measuring my back. I told him the story of my first wake-up call that I had gained weight: I ran down the stairs and my back jiggled. I paused in mid-step and thought, "WHAT THE HECK JUST HAPPENED?" Not that that inspired me to try to lose weight or anything - that didn't happen until a few years later.
So anyway. My body fat measured at 27%. That put me right in the middle of the 'Acceptable' range, because I'm 41. At age 39, the same exact measurements would put me at 24%, which is teetering on the edge between 'Acceptable' and 'Fit.' (That was likely true, because I trained for my marathon that year). The reason it changes with age is the sad fact of sarcopenia. (Spell check just tried to correct that to 'sarcophagus' - thanks, jerk). Sarcopenia is the gradual deterioration of muscle tissue with age. Note that this does not mean we are biologically required to become frail and weak with age. It just means we have to work harder to build muscle and preserve our posture and bone density. I want that for myself. I want to retain my independence until the ripest old age I can reach.
The next step was to calculate how many pounds of body fat and how many pounds of muscle tissue I likely have. I'd rather do this with mathematics than through an autopsy, if you know what I mean. I don't need actual vivisection to trust the science. It was roughly 33 pounds of fat and 90 pounds of muscle-slash-bone, blood vessels, organs, etc. Much of that body fat I will keep. The desirement is to BUILD MUSCLE. If I gain twenty pounds of muscle, I will walk around aggressively pulling up my shirt and flaunting my midriff at everyone. Weight gain is excellent when it's planned and intentional and made up of TRUE GRIT, aka muscle. I love muscle. I want to be eighty and be so ripped I freak people out and make them immediately grab their phones and call someone to tell them. "Dude, I just saw the most jacked grandma!"
Some body fat charts rate percentages as "overfat," "healthy," and "underfat." These are designed for average people, not active people. The concern would be for a gaunt person (perhaps elderly) who wasn't eating enough. I don't think there are (or were) enough muscular, athletic people to measure for these studies. There is a huge difference between someone who has lower body fat due to malnutrition, and someone who has lower body fat due to physical strength and stamina. I haven't yet seen a chart estimating average lean body mass and suggesting that certain ranges are "undermuscled." I would have fit in that category in my late twenties and early thirties, even when I was obese, because I was so unfit I couldn't climb a single flight of stairs without seeing black spots.
Two weeks later, the trainer took my measurements again. I had already dropped from 27% to 24.6%. I had lost two pounds of body fat and gained 3.5 pounds of lean mass. I had trouble believing it, but a pound of fat a week is totally plausible. I have made dramatic physical transformations in the past, and I have also been training really hard. I have something like forty minutes of isometric and body weight resistance exercises to do every day, not including my twice-weekly training sessions and trying to go to yoga a couple of times. I've been consciously correcting my posture while I walk and sit throughout the day. On my frame, I can burn a pound of fat and build a pound of muscle at approximately the same rate. That's why weighing in on a scale without measuring inches or body fat can be so discouraging. Technically I "gained weight" while adding muscle and dropping fat.
Usually when I gain weight it's because I went on vacation and ate too many chimichangas.
I wouldn't have bought into the idea of having my body fat measured when I was younger. That's because nobody under age thirty-five really, truly believes in the concepts of aging, mortality, or death. The ego simply won't allow it. As I get older and watch my friends and family members go through surgery or become dependent on pharmaceuticals and medical appliances, I've started to believe. I'm forty-one, and yes, death will happen to me, perhaps later today. I do have to die, but I don't have to become frail or infirm. I don't have to believe that aging is crippling. As I compare myself with sixty-year-olds instead of twenty-year-olds, I set my sights on those who are still lean, active, and happy. I hope to turn eighty one day, and to celebrate by sitting on the floor and standing up again. That's why I rely on health metrics, to keep me informed and to keep me honest with myself.
I've been working with chronic disorganization, squalor, and hoarding for over 20 years. I'm also a marathon runner who was diagnosed with fibromyalgia and thyroid disease 17 years ago.