If your weight is above average for your height, it doesn’t necessarily mean you’re overweight. That’s the upshot of new research out of the University of California-Santa Barbara that suggest the once-vaunted BMI is not an accurate measure of overall health.

In what could be the death knell for the BMI (body mass index), UCSB psychologist Jeffrey Hunger and colleagues argue that you can be fit and still be overweight. In fact, the UCSB research, published in the International Journal of Obesity, suggests that 34.4 million Americans labeled overweight or obese based on their BMI are, in fact, "perfectly healthy" — as are 19.8 million who are considered obese.

Hunger, a doctoral student in UCSB's Department of Psychological & Brain Sciences, argues that BMI is a deeply flawed measure of health.

"In the overweight BMI category, 47 percent are perfectly healthy," he said. "So to be using BMI as a health proxy — particularly for everyone within that category — is simply incorrect. Our study should be the final nail in the coffin for BMI."

Using data from the long-running National Health and Nutrition Examination Survey, Hunger and his colleagues analyzed the link between BMI — calculated by dividing a person's weight in kilograms by the square of the person's height in meters — and several health markers, including blood pressure, blood sugar and cholesterol.

The results showed that more than 2 million people identified as "very obese" — having a BMI of 35 or higher — are, in fact, healthy. That's about 15 percent of Americans so classified. The findings also revealed that more than 30 percent of those with BMIs in the "normal" range — about 20.7 million people — are actually unhealthy based on their other markers.

"Not only does BMI mislabel 54 million heavier individuals as unhealthy, it actually overlooks a large group of individuals considered to have a 'healthy' BMI who are actually unhealthy when you look at underlying clinical indicators," said Hunger. "We used a fairly strict definition of health. You had to be at clinically healthy levels on four out of the five health indicators assessed."

Many companies use employees' BMI as a factor in determining their health insurance costs. And a new rule proposed by the Equal Employment Opportunity Commission could mean people with a BMI higher than 25 (the "healthy" range is 18.5 to 24.99) could pay higher health insurance premiums.

"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," Hunger argued.