The Current

BMI 'obsolete' and doesn't measure health, says doctor

The Body Mass Index (BMI) determines the weight of health care plans, medical insurance, even eligibility for surgery. But some doctors say it's bogus.
People with a high Body Mass Index (BMI) level could also be perfectly healthy, says obesity researcher Dr. Arya Sharma, who wants to see the test eliminated in medical practice. (VGstockstudio/Shutterstock)

Read story transcript

The value of a simple standardized test to determine Body Mass Index (BMI) — which measures weight relative to height — is under scrutiny as a growing number of health professionals say it's not the best way to assess health or obesity.

"You simply cannot step on a scale and decide whether you're healthy or not," Dr. Arya Sharma says, founder of the Canadian Obesity Network. "That's not how the body works and that's not what the evidence shows."

He tells The Current's Anna Maria Tremonti that the evidence supporting the use of BMI in medical practice is "largely obsolete."
Is your body mass index an accurate indicator of how healthy you are? (Jamiesrabbits/flickr cc)

"[BMI] is largely opinion based and has very little to do with actual data showing that you know BMI makes any real difference to outcomes of surgeries in general." 

While BMI can determine the size of a person, how big someone is, "it doesn't tell you whether that person has health problems," Dr. Sharma explains.

"It doesn't tell you whether that person is physically fit … In fact it doesn't even tell you that that person has excessive body fat."

Whereas BMI is not relevant in the medical practice according to Sharma, he believes it can be useful population surveillance for statistical purposes.

"If you want to know where the people in Canada in general are getting larger, BMI is great for that."

Overweight but healthy

Melody Harding, a 29-year-old woman in Nova Scotia wants the government to stop using BMI to determine who qualifies for provincially-funded breast reduction surgery.

Harding's BMI is deemed too high to get the surgery she says would change her life.
Melody Harding is calling on the Nova Scotia government to change its BMI policy so she can be eligible for breast reduction surgery. (Submitted by Melody Harding)

"I have broken into near hysterics because of my chest more times than I can count. It affects every aspect of my life, even down to my social life and I'm honestly sick and tired of having to deal with this, and I'm also sick and tired of the government refusing to help me with this situation," she tells Tremonti.

Harding wears a 38 N bra size and says that she's not debilitated by her weight, but she is by her chest.

"I am considered obese on the BMI scale. My current BMI is about 46 and that is part of the stickler point for me because I am overweight but I still am you know pretty healthy," she says.

BMI tool useful to a point

Dr. Scott Kahan knows BMI can be imperfect, such as in Harding's case where simply using the tool without context could lead to wrong conclusions. 

But Dr. Kahan, director of the Washington-based National Center for Weight and Wellness still sees BMI as a convenient, useful screening tool. 
Dr. Scott Kahan says BMI is a good, quick health indicator as long as there's context. (

"I certainly use BMI on my patients but I always then further that basic screening with more in-depth evaluation and assessment and testing when appropriate to best understand what that patient's weight and health status is," he tells Tremonti.

When it comes to making policy, Dr. Kahan says rule of thumb is reasonable to use but only to a point.

"There should be a mechanism to evaluate on a case-by-case basis in order to minimize errors that these generalities can lead to occasionally, as in the case of Melody," Kahan explains.

"I know it's a tough situation for her but I'm glad that she's not just sitting down and taking it but rather trying to be an advocate for her and ultimately for other people."

Listen to the full segment at the top of this web post.

This segment was produced by The Current Ines Colabrese, Sam Colbert, Seher Asaf.