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Calculate your BMI

Calculate your BMI
NYT
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First Published: Tue, Sep 11 2007. 12 53 AM IST

Updated: Tue, Sep 11 2007. 12 53 AM IST
What is the most accurate way to measure body fat? Let our guide help you figure it out. If the body mass index (BMI) is accurate, then Mel Gibson, Mike Tyson and Arnold Schwarzenegger all fall into the obese category. And there lies the problem with the BMI, used to calculate body fat based on height and weight. It is often inaccurate because it does not take into account the role that muscles play in the equation. Here’s a rundown on ways to measure body fat:
Online BMI calculator: Just punch in your height and weight.
How accurate it is: Within 10 percentage points of immersion testing, considered the gold standard.
Pros: Inexpensive and easy.
Cons: Not as accurate for muscular types and the elderly.
Where to find it: www.bmi-calculator.net; www.nhlbisupport.com/bmi/; www.caloriecontrol.org.
Waist-hip ratio: A tape measure is used around the waist and hips.
How accurate it is: Not very.
Pros: It is an important predictor of disease. A recent study by University of Texas Southwestern Medical Center, Dallas, researchers found that people with a larger waist-to-hip ratio may be at increased risk for heart disease.
Cons: Does not tell how much fat a person has, just where he stores it. So someone who is overweight may have hips that are a lot larger than her waist. The ratio is good, but she’s still overweight.
Where to find it: www.bmi-calculator.net/waist-to-hip-ratio-calculator/.
Pinch test: Calipers measure folds of skin and fat.
How accurate it is: Not precise but better than the two previous methods. Margin of error is plus or minus 3 percentage points.
Pros: Inexpensive and easy.
Cons: It’s not practical to do this test on someone who is 5’ 2” and weighs 230 pounds (about 105kg) because she has more inches of skin than the calipers can get around. It’s hard to find the right places to pinch every time. It’s best to have the same person do repeated tests.
Where to find it: Many fitness centres offer it.
Bioelectrical impedance test: Person holds device in hands and a sensor sends a harmless radio frequency pulse through the body. It measures fluid content.
How accurate it is: Margin of error is plus or minus 4 percentage points. If person is dehydrated, the reading may be altered.
How it works: Ideally, people should be completely nude before the test begins. After they expel all the air from their lungs, they are repeatedly submerged in water for five to 10 seconds.
How accurate it is: Very. Margin of error is plus or minus 1 percentage point.
Pros: It is the gold standard; the most accurate assessment of body composition
Cons: It can be scary for someone who has a fear of being under water. And did we mention you should be nude?
Where to find it: It is not widely available.
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First Published: Tue, Sep 11 2007. 12 53 AM IST