You entered your height and weight in the calculator on your favorite health website, and it says you’re “healthy.” Case closed, right? Wrong. Weight and body mass index may well be the go-to numbers for defining obesity and related health risks, but they fall far short for many people.
Nearly 70 percent of American adults are overweight, according to the Centers for Disease Control and Prevention. This designation suggests you’re at a greater risk for heart disease, diabetes and certain types of cancer. But whether it’s these health risks or simple vanity that has you concerned about your weight, understand that there may not be one perfect way to measure what constitutes a healthy weight. Determining where you fall within the spectrum could involve far more than putting a few numbers into an online calculator.
Body Mass Index: Simple but Imperfect
The concept of BMI has been around for centuries but was popularized in a 1972 journal article by scientist Ancel Keys. In it, Keys referred to BMI as a useful metric for population studies but not necessarily for evaluating individuals. Even so, today it’s the standard measurement of healthy weight used by the CDC, the World Health Organization and doctors everywhere, to identify people who may be at risk of obesity-related diseases, in part because it’s a simple, fast and virtually cost-free analysis.
“BMI is strongly correlated with the gold-standard methods for measuring body fat,” according to the Harvard School of Public Health. For average people and for large population studies, BMI can be an accurate estimator of healthy weight. But when you look at individuals, many don’t nestle comfortably in the “average” classification.
“BMI gives me an idea of what weight range patients are in,” says Peter LePort, medical director of MemorialCare Center for Obesity at Orange Coast Memorial Medical Center in Fountain Valley, California. “But that depends on a lot of other factors, too, so that’s sort of just what you begin with.”
Height and weight can’t tell the entire story. Case in point: athletes. They can have low body fat with a lot of muscle, work out daily and eat well, and still be considered overweight or even obese according to BMI.
One study, published in the journal Medical Hypothesis, found that BMI correctly identified weight-related health risk in only 66.5 percent of women and 62.7 percent of men, as compared with personal body fat measurements, which increased correct classifications by 7.2 percentage points and 13.4 percentage points, respectively. Further, some evidence suggests BMI isn’t as reliable for larger population studies as Keys intended.
Body Composition: Muscle vs. Fat
If BMI is a jumping-off point for determining just how healthy your weight is, body fat percentage is the next step.
“Muscle is much denser and heavier than fat,” explains LePort, who says you can see a prime example of this in people who choose to get healthy by dramatically increasing exercise. “So the next time you see them, they look like they’ve lost a lot of weight and they’re thin, but in actuality they haven’t lost any weight. What they did lose was body fat, and they gained muscle.”
Measuring how much of your weight is fat can do away with the shortcomings of BMI that appear for those who are athletic and have a high percentage of muscle per body weight, for instance. But it goes both ways, as body fat analysis may also pick up risk factors that BMI doesn’t.
A 2012 study published in the International Journal of Obesity found that among 6,123 participants, 29 percent of those classified as lean under BMI standards and 80 percent who were classified as overweight actually had body fat percentages that made them obese. Further, they had additional elevated risk factors that wouldn’t have been identified had their doctor relied simply on BMI.
Waist Circumference
But neither BMI nor body fat percentage can completely account for an increasingly identified risk factor: body shape. Several studies have noted the link between having an “apple shape” — a larger waist circumference — and various health risks. One of those, the Nurses’ Health Study, which followed nearly 45,000 U.S. women, found after a 16-year follow-up that higher waist circumference was associated with higher risk of cardiovascular disease-related death even among those women classified as having normal weight. It’s also higher waist circumference, not BMI, that accounts for higher rates of Type 2 diabetes in the U.S. compared with England, according to the Journal of Epidemiology and Community Health.
So to your scale and body fat calipers, be sure to add a tape measure.
What’s a Healthy Weight For You?
LePort, who’s been practicing for 30 years and specializing in bariatric surgery since the late-1980s, says there’s nothing wrong with tracking your health using weight and body fat, but the first step in getting an accurate picture lies in honest self-reflection.
“That’s probably the biggest part of this, because you have a lot of people who are overweight and don’t realize it. They think this is normal,” he says. “They think they’re eating normal, doing the normal amount of exercise, but in reality they never really eat a healthy meal and their daily exercise is going up and down a flight of stairs.”
He says there’s no reason people concerned about their weight and health shouldn’t have their body fat tested, as it gives them “something to really put their hands on,” and more case-specific information than just height and weight measurements. Further, he says, weighing yourself on a regular basis is a good practice in self-monitoring, as long as you don’t attach anxiety or self-depreciation to the numbers you see — because, again, they’re only part of the equation.
All of the research and expert opinion seems to arrive at this conclusion: “Healthy weight” is not one simple measurement that can be taken independently of someone’s unique life and health circumstances. Instead, it’s a variety of measurements and analyses that give the most accurate picture of health. A closer look that involves body composition, diet and activity analysis, as well as the influence of additional risk factors (like smoking) is a better judge of health, though it may take some extra effort to get.
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Weighing Your Health: Where BMI Falls Short originally appeared on usnews.com
