Beyond BMI: Study shows obesity shortens life, but trainer cautions body mass index isn't only measure of health
Tuesday, March 24, 2009
A highlight in Allyson Langley's pursuit of fitness came from a young player on her soccer team just about two weeks ago.
"He said, 'Coach Allyson, Where did your belly go?' I thought that was so cute!" she said, laughing.
Langley, 23, said she sculpted an "an ideal body" by swimming daily during her high school days. She carried just 115 pounds on her 5-foot-1 frame. In college, her fitness routine fell apart.
"At my heaviest, I was 155 pounds," she said. Her height and weight translated to a 29.9 body mass index and the risk of obesity. After months of work, she weighs 132 and has a 24.9 body mass index, which is normal.
A new study published by the British medical journal Lancet suggests carrying too much weight can shorten a person's life by as much as 10 years.
Researchers at the University of Oxford analyzed 57 studies, mostly in Europe and North America, following nearly one million people for an average of 10 to 15 years. During that time, about 100,000 of those people died. The researchers focused on body mass index — the measurement that divides a person's weight in kilograms by their height squared in meters to determine obesity — and found that death rates were lowest in people who had a BMI of 23 to 24, on the high side of the normal range. Normal BMI is 18.5 to 24.9.
"Body mass index is a great standard that allows us to use each individual's measurements calculated into one number for research on groups of people and their relationships to many heath issues, " said Justin Franke, physical therapist at Select Physical Therapy Clinic in Jackson.
Health officials generally define overweight people as those with a BMI from 25 to 29, and obese people as those with a body mass index above 30.
The study found that people with a BMI from 30 to 35, considered moderately obese, lost about three years of life. People who were morbidly obese — those with a BMI above 40 — lost about 10 years off their expected life span, similar to the effect of lifelong smoking.
Moderately obese people were 50 percent more likely to die prematurely than normal-weight people, said Gary Whitlock, the Oxford University epidemiologist who led the study. He said obese people were up to four times more likely to die of diabetes, kidney or liver problems and one sixth more likely to die of cancer.
Joel Ramdial, a certified personal trainer who works with Langley, said body mass index can be a valuable tool as a general measure of body fat, but pointed out it doesn't differentiate between types of bodies or between men and women. Women need more fat on their bodies for general reproductive health, he said.
He uses calipers for skin fold tests that gently pull skin and fat away from muscles and calculates those measurements into a percentage of body fat.
"If two people were both 5-foot-5 and weighed 135, they would have a BMI of 22.5, which is considered normal," he said. "But if you had one who had 10 percent body fat, they might have 13.5 pounds of fat and the other might have 30 percent body fat, which is 40 pounds of fat. For a guy that would be too high, but for a woman, that would be considered acceptable."
Franke said people who do want to use body mass index as a measure shouldn't rush to get the best number.
"The only way to reach a healthy body mass index and keep it is lifestyle change," he said. "That means continuing to go to the gym and staying away from the potato chips and the baked goods that have entire sticks of butter."
For Langley, who works as a coach at Class Act Family Fitness in Jackson, working out has been a stress reducer in addition to a fitness regime, and she said expects to continue working out regularly.
The Associated Press contributed to this report.
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