Did relying on BMI measurements cause Oprah to fall victim to yo-yo dieting? Perhaps — if we’re to follow the findings of a new study published April 3 in the journal PLoS One. Best known for her blockbuster talk show, African-American billionaire Oprah Winfrey has been called “arguably the world’s most powerful woman” by CNN and Time.com.
For a time the world’s only black billionaire, she’s also definitely one of the most influential persons of the 20th century. Her story of triumph against overwhelming odds — born into poverty in rural Mississippi to a teenage single mother, raised in an inner-city Milwaukee neighborhood, raped at age nine, getting pregnant at 14 and having her son die in infancy, but going on into wealth and fame — will continue to inspire thousands of people across the world.
Immensely successful as a talk show host, actress, producer and now media owner, she’s often praised for overcoming adversity to become a benefactor to others.
But there’s one struggle that she seemingly hasn’t overcome — that’s the one against obesity. Throughout her career, Oprah’s yo-yoed from 140 lbs to 200 lbs and back again and she’s been very public about what she calls her struggle against food addiction.
But could the culprit be less complicated than an addiction? Could it be that she was simply using a wrong measure of her body fat — and consequently going on the wrong ways — weight loss — to become fit? Is losing weight the wrong approach for overweight and obese people like Oprah?
With the United States and the rest of the developing world thick in the middle of an obesity crisis, that’s a million-dollar question. And the answer is: maybe.
That is, according to the new study by researchers from the New York University School of Medicine and New York’s Weill Cornell Medical College.
The study suggests that while the body mass index — the formula used to distinguish between healthy and unhealthy weight — has been used for 180 years, it may be incorrectly classifying people as having healthy weights when their body-fat composition shows that they are really obese.
According to the study, BMI misclassified up to 39 percent of participants, allowing them to fall under the “overweight” category when they are actually “obese.” BMI misclassifies about half of women and just over 20 percent of men, the study claims.
BMI is a simple calculation based on a person’s height and weight that gives a score used to diagnose obesity. A person with a BMI of 30 or more is classified as obese — and public health authorities like the U.S. Centers for Disease Control use this measure to find out how many Americans are obese.
Right now — based on their BMIs — at least one in three Americans are obese. As the rising numbers of obese Americans is causing threatening to bring on a looming burden of disease in the next few years, health experts are scrambling for better ways to measure the fatness — also a measure of nation’s state of health and way to judge the success or failure of treatment programs.
But relying on BMI leads people to on-off weight loss programs. In an interview with the Los Angeles Times, researcher Dr. Eric Braverman claims the widespread use of BMI was “feeding the failure” of public health policies and treatments aimed at fighting obesity.
If medical interventions had encouraged patients to shift their body composition toward lean muscle mass — instead of focusing on losing weight — there would have been less fat people, Dr. Braverman believes.
What happened instead was that patients were encouraged to shed extra pounds — and while this produced weight loss in the short term, patients rebounded by eating more, regained the weight in the long term and became fatter, Dr. Braverman says.
Fat-muscle ratio, new gold standard?
Instead, Dr. Braverman’s team suggests that a person’s the ratio of fat to lean muscle mass is a better measure of healthy weight. This fat-muscle ratio is a better indicator of a person’s risk for health problems — and should be used as the new “gold standard” for detecting obesity, the researchers suggest.
To measure fatness, a diagnostic test called dual-energy X-ray absorptiometry — or DXA — is used and obesity is calculated based on fat-composition standards used by the American Society of Bariatric Physicians.
To come up with their findings, the researchers from the New York universities looked at records of 1,393 people who had both their BMI and body fat scores measured. While the data showed that the two measures came to the same conclusion most of the time, 539 participants — or 39 percent — were not classified as obese according to their BMIs — even if their fat percentage suggested they were.
Because of using this poor measure of fatness for many years, the U.S. “may be much further behind than we thought” in addressing the nation’s crisis of obesity, write the study’s authors, Dr. Nirav R. Shah, New York’s state commissioner of health, and Dr. Braverman, a New York City internist in private practice. The 1,393 patients in the study were from his Manhattan practice.
The researchers say the disparity was greatest in women and worsened when looking at older groups of women. “Greater loss of muscle mass in women with age exacerbates the misclassification of BMI,” they argue.
Thus, shifting to the new measure of fatness will impact women more: Using the new fat-muscle ratio instead of BMI, 20 percent of the men in the study shifted from being categorized under “normal and healthy” into the “obese” column. By contrast, half of the women shifted from being classified as “healthy” to “obese.”
The researchers also propose changing the thresholds for obesity: “A more appropriate cut-point for obesity with BMI is 24 for females and 28 for males.” Currently, a BMI of 24 is classed as a “normal” weight.
A range of alternatives
“This is a technique or method that holds promise,” says Dr. James Hebert of the new fat-muscle ratio. Dr. Herbert is an expert on obesity-related diseases at the University of South Carolina who wasn’t involved in the study. “There’s a casting about for better ways to address the public health problem of obesity. And to do so, you have to measure the problems and their public health consequences.”
A wide range of alternatives to the BMI have been proposed in the last two years to measure the effectiveness of interventions such as weight-loss counseling, exercise regimens and drug therapies. These include simple measures like waist circumference, hip circumference and waist-to-hip ratios.
More recently, a computer program has been developed to analyze a series of patient photographs and to recognize — based on known patterns of musculature and fat deposition — dangerous fat better than the BMI alone. This method is being explored by University of Alabama researchers.
Experts praise this University of Alabama effort to calculate obesity, since the DXA scans — now used to evaluate bone density — may prove too expensive for widespread use.
Replacing imperfect indicator with another imperfect one
But some experts are concerned that the new measure being proposed by the study is just as imperfect as the older one.
While “it’s important to point out the weakness of the BMI,” the study authors “have chosen an arbitrary measure of obesity, particularly from the point of view of risk” says Dr. Richard N. Bergman, director of Cedars-Sinai’s Obesity and Diabetes Research Institute in Los Angeles. “It’s a poor measure of fatness, and we do need better measures.”
While the BMI has its shortcomings, the link between the BMI and cardiovascular disease, type 2 diabetes, certain cancers and other diseases has been established by decades of research, Bergman points out.
At this point, the precise level at which body fatness — as measured by DXA — contributes to such diseases is not yet established. Without the evidence of years of study, it’s not possible to know for sure whether higher DXA scores actually translate into poorer health.
Combining leptin with BMI
To get a more accurate picture of a patient’s body fat, Dr. Braverman’s team suggest combining BMI with a blood test to measure leptin. This may be a simpler, cheaper and more reliable to measure obesity, the researchers also say.
Leptin, an appetite-boosting hormone secreted by the body’s fat deposits, circulates in the bloodstream and is strongly correlated with body fat. Because leptin levels generally follows the same track as the level of fatness as measured by DXA, they can be used to distinguish people with healthy levels of body fat from those carrying too much, the researchers say. Leptin blood levels range from 0 to around 200, and Dr. Braverman says optimal levels are under 5.
Dr. Braverman urges doctors to consider taking routine measures of patients’ leptin levels as a useful indicator of body composition and a possible predictor of obesity-related disease. Like cholesterol and blood pressure, leptin could become a valuable indicator of disease risk, he says.
Where costs are concerned, researchers think measuring blood concentrations of leptin could someday cost as little as US$1 — way cheaper than the US$300 a DXA scan costs. Since DXA scans are done to assess osteoporosis risk, patients who get a DXA test to measure bone loss should have their body fat assessed as well, he suggests.
But it’s unclear if a leptin blood test can help doctors better assess risk for the so-called ‘metabolic’ conditions like diabetes and heart disease, weight loss surgeon Dr. Mitchell S. Roslin, of Lenox Hill Hospital in New York City, points out.
Yes, the BMI alone can be an inaccurate measure of such risk, he admits. But blood leptin levels may also be inaccurate. “Blood leptin level may be a more accurate measure of body fat, but when you factor in what you know about a patient — such as if they are sedentary or active — I’m not sure it tells you much,” he says. “There is a relationship between body fat and metabolic disease, but it may not be a linear relationship,” he tells WebMD.