The Ups And Downs Of Measuring Body Fat

Visit the doctor and someone will almost certainly take your temperature, blood pressure and weight. All it takes is a thermometer, arm cuff and a scale. Patients have a pretty good idea what the readings mean. But the tools to measure fat are much more diverse - and each has its drawbacks. First, let’s dispose of a common misconception: “To measure fat, just jump on a scale.â€? Seems logical; it’s what everyone talks about when discussing obesity but a scale is a primary tool to measure...well, weight. It’s precise as far as it goes - weight is an indicator of health - but it doesn’t shed much light on how much fat you’re carrying around, along with bone, muscle, organs and other body content. "Your weight tells you nothing. Your weight tells you nothing," says Gina Shaffer, a personal trainer in Elyria.

Doctors couldn’t agree more. The most common fat measurement they use is low-tech. It’s called the Body Mass Index. You’ve probably heard of it, but not a lot of people can rattle off their BMI number. MetroHealth’s Dr. Eileen Seeholzer says that’s changing. At her clinic, everyone goes home with a sheet in hand about their B-M-I. "Body Mass Index is basically a ratio of two measurements: a person’s height, and their weight. "The BMI gives you a common number." That’s weight divided by height, squared. There are lots of easy-to-use calculators online to get your personal number. A BMI of over 25 is considered overweight; 30 and above is obese. High BMIs are a red flag for health problems like diabetes and heart disease. But the BMI doesn’t directly measure the fat in your body; it’s just an estimate. It doesn’t breakdown your body composition.

The second fat measurer in our little tour is a gadget, one you might find in a health club or gym. Let’s go back to Gina Shaffer, the personal trainer. "Alright, so take your shoes and socks off." Shaffer is working with Julie Rush from Avon Lake and she’s about to step on a scale at the gym in the EMH Elyria Medical Center. The first thing on Schaffer’s agenda is to get some measurements. "Let me just program this in...and how old are you? Rush: "55." Schaffer: "And how tall?" Rush: "5’ 8â€?." And go ahead and hop on." This isn’t your typical scale. It’s a “bio-electrical impedanceâ€? machine. It sends an imperceptible, safe electric current through the body. The current passes through lean body mass faster than when it encounters fat. By measuring this resistance, the machine computes the amount of fat in the body. Rush gained five pounds since the last check in and she’s a little disappointed. But Shaffer says that’s not the thing to focus on:

There are many other ways to get at a body’s fat content. Calipers – those tong-things a doctor pinches your skin with; an underwater measuring tank. Some can seem a little weird. "We call this the egg," says Alicia Thomas. She runs studies at a MetroHealth research lab. She shows off what’s called the Bod-Pod. "It smells like a boat—it’s made of fiberglass. It has a nice seat in here for the patient…" The Bod-Pod is a high-tech way to precisely measure body fat. It’s used in research, and health spas and clinics. Thomas says it’s quick and safe. "The worst part is that you have to put a bathing suit on." I climb inside to see what it’s like, and they close the hatch. It blows puffs of air at you. It measures fat through changes in air pressure. It’s accurate and expensive. Maybe fun, but is it necessary? "I don’t think I could ever say one needs a bod-pod," Dr. Seeholzer says. She says the main thing is to keep track of your measurements – no matter which method is used. Those who do tend to make more progress with their health goals.