Your fat-and how to find it
Ever look at the scale and reason, "maybe I'm just big boned? The truth is, weight by itself is an imperfect measure of what shape you’re in. to truly gauge your health risks, you need to know your body fat.
Ever look at the scale and reason, "maybe I’m just big boned?
The truth is, weight by itself is an imperfect measure of what shape you’re in. to truly gauge your health risks, you need to know your body fat.
“Fat is your predictor of mortality, and it needs to be measured directly,” says Eric Braverman, M.d., author of Younger (Thinner) You Diet. “the average person loses 15 years by being obese.”
That’s a pretty hefty figure, especially considering America’s rising obesity rate: From 2007 to 2009, that rate jumped from 25.6 percent to 26.7 percent. but with so many methods that purport to help you figure out how much fat is on your frame, how can you separate the bull from the bonafide? Here’s the skinny on several techniques:
Body Mass Index (BMI)
What it is: a simple formula (weight in kilograms divided by height in meters squared, or kg/m2) evaluates your weight relative to your height. In general, the higher your bMI, the more body fat you’re likely to have. to find out yours, head to www.nhlbisupport.com/bmi.
Is it accurate? Well, not exactly, since it doesn’t factor in a person’s muscle mass. take lean, well-trained athletes, for example: their weight may force their bMI up into the overweight or obese range, even though they carry very little fat.
But the flip side, says Dr. Braverman, is even more disconcerting: “Most americans are more out-of-shape than their bMI suggests. It may fall into the normal range despite extra flab.”
What should you shoot for? Normal bMIs range from 18.5 to 24.9 for both men and women; overweight ranges from 25 to 29.9; and a BMI above 30 indicates obesity.
Waist Circumference
What it is: A standard-issue tape measure is used to measure your waist size—the higher the number, the bigger your belly. Why it matters: Excess abdominal fat is proven to put folks at greater risk for type 2 diabetes, high blood pressure, high cholesterol, coronary artery disease and more.
Is it accurate? Yes—provided you don’t cheat. So no sucking in your stomach or pulling the tape too tightly. Simply measure around your bare belly, right above the navel, keeping the tape parallel to the floor.
What should you shoot for? More than 40 inches puts men at higher-than-average risk for developing obesity-related illness; for nonpregnant women, the threshold is 35.
Skin-fold measurements
What they are: Calipers are used to measure the thickness of skin folds on three to seven areas of the body, such as upper arm, belly and thigh. The measurements are then plugged into a formula to calculate body-fat percentage. (Find detailed instructions plus the fat-percentage calculator at www.brianmac.co.uk/fatyuhasz.htm.)
Are they accurate? Sure … if you’re pinching the right spots at the right time and in the proper way, if you’re not very overweight and if you record the measurements within five seconds. It helps to be a contortionist. In short, skin-fold measurement requires precision that can be difficult to achieve by oneself.
What should you shoot for? See the chart for ideal body-fat percentages.
Bioelectrical Impedance Analysis (BIA)
What it is: To measure your body-fat percentage, a device assesses the flow of a harmless electrical current through your body. (Some bathroom scales will do this analysis for you.) Electricity meets more resistance from fat than from muscle, so the faster the current travels, the leaner you are.
Is it accurate? More or less. Factors such as hydration, skin temperature, time of day, your most recent meal and recent physical activity can affect the reading. So if you just drank water, hit the gym or ate a Big Mac, don’t count on it. But used weekly, at the same time of day, it can be a useful guide. (Note: This method is off-limits for people with pacemakers.)
What should you shoot for? See the chart for ideal body-fat percentages.
Hydrostatic weighing (or Hydrodensitometry)
What it is: Underwater weighing! You enter a tank and a technician calculates your body density by measuring the amount of water you displace. He or she inserts the info into a formula to derive your body-fat percentage.
Is it accurate? Yes, but the tanks can be hard to find and expensive to use. Check out local universities and high-tech gyms.
What should you shoot for? See the chart for ideal body-fat percentages.
Dual-energy X-ray Absorptiometry (DEXA)
What it is: A whole-body scan using low-dose X-rays that shows the body’s fat (along with bone and muscle) and where it’s deposited. (It’s the same machine used to test bone density.)
Is it accurate? Very. In fact, it’s now considered the gold standard in body composition analysis. “Ask your doctor to prescribe it,” says Dr. Braverman, who recommends having “your body fat measured at least as often as your cholesterol.”
What should you shoot for? See the chart for ideal body-fat percentages.
What’s this about neck measurements?
You may have heard about a recent study finding that neck girth may be a good supplement to BMI, especially for children. Why the neck rather than the waist? Experts say figuring out exactly where the waist is may not be as obvious as it seems. The jury’s still out on this one, so if you’re going to rely on a tape measure, stick to your waist for now.
