It’s not the best way. According to a major study published in late 2005, the waist-to-hip ratio is three times more accurate than Body Mass Index, or BMI, at predicting cardiac risk.
The BMI is a ratio of height to weight: over 25, and you’re considered overweight, over 30, and you’re “obese” (The federal government offers a BMI calculator (click HERE). Both put you at increased risk of dying early from heart disease and cancer.
But BMI can be misleading — very muscular people may get a high
score, yet be at low risk.
To calculate your waist-to-hip ratio, get a tape measure and measure your waist, then your hips, then divide the first number by the second. For women, anything over 0.85 indicates increased risk, for men, anything over 0.95, said Dr. Arya Sharma [cq], an obesity specialist at the Population Health Research Institute at McMaster University in Hamilton, Ontario and a co-author of the 2005 study of 27,000 people, with and without heart
disease.
The waist-to-hip ratio is more accurate because it reflects how much abdominal fat a person has. Abdominal fat, the deep, visceral stuff that wraps around organs, is biologically active and secretes chemicals called cytokines that trigger inflammation in blood vessel walls, raise blood pressure, increase the tendency for blood to clot, worsen cholesterol levels and lead to a pre-diabetic problem called insulin resistance.
Put differently, it’s possible to have a good BMI but still be at risk.
“Don’t fool yourself that if your BMI is 22, you’re okay, if your
waist-to-hip ratio is too high,” said Sharma.
Dr. Thomas H. Lee, editor in chief of the Harvard Heart Letter,
cautioned that it can be tricky to measure your hips in the right place. So you can just measure your waist. “If it’s over 35 inches for a woman and over 40 for a man, you’ve got a lot of abdominal fat,” he said. Which means it’s time to lose weight.