Human Limits

Exploring performance and health with Michael J. Joyner, M.D.

Photo of Michael J. Joyner, M.D.

Defining Obesity

This is a short post with some definitions and statistics about obesity.   They will be helpful to understand upcoming posts on the health consequences of physical inactivity and how inactivity and obesity are linked.

First, what is BMI?  BMI stands for Body Mass Index.  It is a mathematical formula that factors in height and weight to give a single number that is useful to normalize values for people of different heights.   This link is to a CDC site about obesity and BMI.  Briefly, a BMI of 20-25 is normal, between 25 and 30 is considered overweight, and more than 30 is obese.   BMI is not a perfect way to estimate body composition, for example there can be super muscular people who have high BMIs and are very lean.  However, for the population as a whole it seems to work.   Here is a link for anyone who wants to take a deeper dive into BMI.  Using the table below you can calculate your own value.  For anyone used to the metric system the table is in feet and pounds because most of my readers are likely in the U.S.












Second, just how fat are we getting as a population?  In the last couple of posts I have talked about the pandemic of inactivity related diseases and just how inactive most people are.  Below is a CDC video showing the trends in obesity by state in the U.S. over the last 30 years.  You can see there is also an obesity epidemic going on in parallel with the inactivity problem and about 35% of the U.S. population is now obese and somewhere between 60-70% are either overweight or obese.  The CDC website has more data on obesity for those who are interested.



click here for video


The data and video speak for themselves and there is no need for much editorial comment except to say it is a very, very disturbing situation.  In coming posts I will make the case that less physical activity has caused this problem and that more physical activity and exercise are key to addressing it.



4 Responses to “Defining Obesity”

  1. August 20th, 2012 at 12:49 pm

    Joey Keillor says:

    It’s seems insane that the change in collective girth has occurred so quickly. In the video, not only do states get darker shades of blue, but then they are forced to add new color categories of hugeness. What was different about 1980 that isn’t true today? McDonalds was there, everyone had a car. People have always resisted exercise…and today there are more runners and races than ever. People keep coming up with theories as to why this is happening (eg. NEAT, which doesn’t explain why construction workers are fat, too), but none to me seems to explain the explosion.

    Good luck Dr. Joyner!!

  2. August 22nd, 2012 at 4:28 pm

    Dixie Stanforth says:

    Mike – You ROCK! Can’t wait to share your site with our students! Blessings, Dixie

  3. December 13th, 2012 at 6:31 am

    Progress Against Obesity? | Human Limits: Michael J. Joyner, M.D. says:

    […] obesity epidemic and what to do about it has been a major focus of this blog.   Plug in OBESTIY to the key word […]

  4. January 7th, 2013 at 6:02 am

    BMI, Mortality & Health | Human Limits: Michael J. Joyner, M.D. says:

    […] There was a lot of attention in the press last week about a new report in the Journal of the American Medical Association (JAMA) showing that BMIs in the “overweight” category (25-30) are associated with lower overall mortality rates.   This was accompanied by editorial comments about the need for people to calm down about the fact that U.S. in specific and the world in general is getting fatter.    Before taking a deeper dive into the BMI vs. mortality argument here is a link to a post on BMI, and recent overweight/obesity trends in the U.S. […]

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