Measuring Your BMI Is Probably Pointless

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Here’s some confusing news: That tape measure and scale probably aren’t offering a true indication of your health after all.

In a new study published in the  International Journal of Obesity, researchers from the University of California, Santa Barbara (UCSB) and University of California, Los Angeles (UCLA) found that calculating someone’s BMI — body mass index, a measurement of body fat based on height and weight — may be ineffective, since millions of “perfectly healthy” Americans are being mislabeled as either overweight or obese.

The study investigators used data taken from the most recent National Health and Nutrition Examination Survey to examine the link between BMI and other vital health factors, including blood pressure, blood sugar, and cholesterol.

More than two million Americans who were categorized as very obese (with a BMI of 35 or higher), 19.8 million who were considered obese (with a BMI between 30 and 34.9) and 34.4 million who were overweight (with a BMI between 25 and 29.9) are actually healthy by other markers, researchers found. 

So how could someone with a BMI over 25 — especially an individual who falls under the obese category — be considered “perfectly healthy?”

“I think it’s because a person’s BMI doesn’t speak to their behaviors,” Jeffrey Hunger, a doctoral student in UCSB’s Department of Psychological and Brain Sciences, and co-author of the paper, tells Yahoo Health. “Although our study can’t speak directly to this issue, I suspect that lifestyle factors, such as being active, are more important than BMI in predicting actual health. Generally speaking, we need to end the laser focus we have on weight and start truly focusing on health.”

Hunger and his team also concluded that nearly 30 percent of people with a “normal” BMI — an average of 20.7 million Americans — are actually unhealthy. “Again, I think this can best be explained by the crude nature of the BMI,” adds Hunger. “It’s overly simplistic to think that height and weight will adequately capture health.”

Hunger believes an integrative approach will offer a true assessment of one’s wellbeing. “We need to move away from trying to find a single metric on which to penalize or incentivize people and instead focus on finding effective ways to improve behaviors known to have positive outcomes over time,” he says. “The closer we can get to actual markers of health, the better. This includes clinical indicators like those used in our study, such as blood pressure, blood sugar, cholesterol, as well as behaviors that we know are important for long-term health like eating well, staying active and getting enough sleep.”

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