Docs on Call
What BMI Can—and Can't—Tell You
Clip: 4/23/2026 | 58sVideo has Closed Captions
A physician explains how BMI defines obesity and where the measure can fall short.
Dr. David Tennant explains body mass index, or BMI, and how it uses height and weight to classify people as normal weight, overweight or obese. He also discusses the measure's limitations, including people with greater muscle mass, while describing BMI as a simple and inexpensive estimate that works reasonably well for many patients.
Problems playing video? | Closed Captioning Feedback
Problems playing video? | Closed Captioning Feedback
Docs on Call is a local public television program presented by WTVP
Docs on Call
What BMI Can—and Can't—Tell You
Clip: 4/23/2026 | 58sVideo has Closed Captions
Dr. David Tennant explains body mass index, or BMI, and how it uses height and weight to classify people as normal weight, overweight or obese. He also discusses the measure's limitations, including people with greater muscle mass, while describing BMI as a simple and inexpensive estimate that works reasonably well for many patients.
Problems playing video? | Closed Captioning Feedback
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Learn Moreabout PBS online sponsorshipWhat's the difference between being overweight, being obese, being morbidly obese?
- Yeah, all good questions.
So it's usually defined based on the body mass index.
And it's nice because it's easy to do.
You can do it essentially for free.
It's just your weight versus your height.
The basic idea is if someone's 200 pounds, well, are they five feet or are they six feet, right?
This is a different thing in terms of how much fat you're likely accumulating on your body.
But it's broadly defined, below 25 is normal, 25 to 30 would be overweight, and then 30 plus body mass index is obese.
And when you get to be above 40, then that's class three or morbid or severe obesity.
And it's not like totally perfect.
You know, some people have more muscle bulk than others, and you kind of know it when you see it.
I looked it up once.
The average BMI of the starting linebacker core for the Chicago Bears, and I think they were on average obese.
These people are obvious.
They're just incredibly muscular.
But for most people, most of the time, it's a pretty good, inexpensive estimate of where we are.
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Docs on Call is a local public television program presented by WTVP