# Did the rates of 'overweight' people double since 1990 because the BMI changed? **URL:** \ **Category:** Factual Questions\ **Created:** [May 12, 2004, 6:24pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826 "2004-05-12T18:24:17Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [May 12, 2004, 6:24pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/1 "2004-05-12T18:24:17Z")
I recently read something that said the main reason people are ‘fatter’ and there are 2x as many overweight people (by BMI standards) today than in 1990 is because in 1990 a BMI of 27+ was considered overweight but in 1998 or so it was changed to 25. This added tens of millions of normal people into the ranks of the overweight, which is why the rates for obesity are said to have doubled. Is this true? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [May 12, 2004, 6:29pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/2 "2004-05-12T18:29:50Z")
I doubt that any significant number of people have ever ranked themselves according to the BMI for the BMI to be considered as having any significant inlfuence over staggering numbers of obese people. Death doesn’t even make a dent the other way. ---
**Author:** ![tremorviolet](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@tremorviolet](https://boards.straightdope.com/u/tremorviolet)\ **Post date:** [May 12, 2004, 6:40pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/3 "2004-05-12T18:40:52Z")
No, it’s not true (with a qualifier). It is true that the the definition of overwieght changed in 1989 ([cite](http://www.halls.md/bmi/history.htm)). But, the number of people with higher BMI’s (no matter what you call it) has also increased dramatically over the last twenty years. > [@](#): > > The prevalence [of overweight and obesity] has steadily increased over the years among both genders, all ages, all racial/ethnic groups, all educational levels, and all smoking levels.10 From 1960 to 2000, the prevalence of overweight (BMI \> 25 to \< 30) increased from 31.5 to 33.6 percent in U.S. adults aged 20 to 74.[9] The prevalence of obesity (BMI \> 30) during this same time period more than doubled from 13.3 to 30.9 percent, with most of this rise occurring in the past 20 years.8 From 1988 to 2000, the prevalence of extreme obesity (BMI \> 40) increased from 2.9 to 4.7 percent, up from 0.8 percent in 1960.3,8 In 1991, four states had obesity rates of 15 percent or higher, and none had obesity rates above 16 percent. By 2000, every state except Colorado had obesity rates of 15 percent or more, and 22 states had obesity rates of 20 percent or more.11 The prevalence of overweight and obesity generally increases with advancing age, then starts to decline among people over 60.[3] [source page](http://www.niddk.nih.gov/health/nutrit/pubs/statobes.htm#preval) For more information on overweight criteria, see [here](http://www.halls.md/body-mass-index/overweight.htm). ---
**Author:** ![Satyricon](https://avatars.discourse-cdn.com/v4/letter/s/f05b48/32.png) [@Satyricon](https://boards.straightdope.com/u/Satyricon)\ **Post date:** [May 12, 2004, 7:49pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/4 "2004-05-12T19:49:01Z")
While the general population has gotten heavier over the years, the BMI chart is an unreliable method of determining if someone is really overweight. This is because BMI only calculates a height:weight ratio. It doesn’t take into consideration muscle and bone mass. In fact most bodybuilders are classified as dangerously obese. I really think it’s time to get a new method of calculating a healthy body weight. ---
**Author:** ![tremorviolet](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@tremorviolet](https://boards.straightdope.com/u/tremorviolet)\ **Post date:** [May 12, 2004, 7:58pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/5 "2004-05-12T19:58:33Z")
> [@Satyricon](#): > > While the general population has gotten heavier over the years, the BMI chart is an unreliable method of determining if someone is really overweight. This is because BMI only calculates a height:weight ratio. It doesn’t take into consideration muscle and bone mass. In fact most bodybuilders are classified as dangerously obese. I really think it’s time to get a new method of calculating a healthy body weight. Yeah, this is true on an individual basis. But, I think BMI are still valid for overall population trends. The percentage of people that BMI is inaccurate for is very, very small. I guaran-dang-tee you that the overall rise in BMI’s in the US is _not_ due to millions of people suddenly taking up weightlifting. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [May 12, 2004, 8:20pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/6 "2004-05-12T20:20:06Z")
> [@Satyricon](#): > > While the general population has gotten heavier over the years, the BMI chart is an unreliable method of determining if someone is really overweight. This is because BMI only calculates a height:weight ratio. It doesn’t take into consideration muscle and bone mass. In fact most bodybuilders are classified as dangerously obese. I really think it’s time to get a new method of calculating a healthy body weight. We’ve been over this before, although it’s a little tough to find a link, as you can’t search for three-letter terms. The BMI is very cheap and quick to measure, and it does give some useful information: people with a high BMI are at a higher risk of death than they would be if their BMI were lower, _even if their overall risk of death is lower than that of the general population_. As for the question in the OP, I seriously doubt it. No competent statistician would run the analysis without making corrections like that. ---
**Author:** ![clairobscur](https://avatars.discourse-cdn.com/v4/letter/c/839c29/32.png) [@clairobscur](https://boards.straightdope.com/u/clairobscur)\ **Post date:** [May 12, 2004, 8:20pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/7 "2004-05-12T20:20:55Z")
> [@tremorviolet](#): > > No, it’s not true (with a qualifier). It is true that the the definition of overwieght changed in 1989 ([cite](http://www.halls.md/bmi/history.htm)). But, the number of people with higher BMI’s (no matter what you call it) has also increased dramatically over the last twenty years. > ]. Does your cite mean that close to 70% of, the US population is overwieghted??? (33.6 overweighted+ 30.9 obese + 4.7 extremely obese) Or did I miss something? ---
**Author:** ![tremorviolet](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@tremorviolet](https://boards.straightdope.com/u/tremorviolet)\ **Post date:** [May 12, 2004, 8:33pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/8 "2004-05-12T20:33:28Z")
> [@clairobscur](#): > > Does your cite mean that close to 70% of, the US population is overwieghted??? > > (33.6 overweighted+ 30.9 obese + 4.7 extremely obese) > Or did I miss something? Yep. Click on the “source page”. It’s a compilation of statistics from the 1999-2000 National Health and Nutrition Examination Survey (NHANES). > [@](#): > > Q: How many adults are overweight? > A: Nearly two-thirds of U.S. adults are overweight (BMI \> 25, which includes those who are obese).[8] > > All adults (20+ years old): 129.6 million (64.5 percent) > Women (20+ years old): 64.5 million (61.9 percent) > Men (20+ years old): 65.1 million (67.2 percent) > > Q: How many adults are obese? > A: Nearly one-third of U.S. adults are obese (BMI \> 30).[8] > > All adults (20+ years old): 61.3 million (30.5 percent) > Women (20+ years old): 34.7 million (33.4 percent) > Men (20+ years old): 26.6 million (27.5 percent) > > Q: How many adults are at a healthy weight? > A: Less than half of U.S. adults have a healthy weight (BMI \> 18.5 to \< 25).[9] > > All adults (20-74 years old): 67.3 million (33.5 percent) > Women (20-74 years old): 36.7 million (35.3 percent) > Men (20-74 years old): 30.6 million (31.8 percent) There do appear to be some rounding or margin of error differences but the numbers are roughly right. Unfortunately, we really do have a horrible problem here in the US (and it’s spreading to other Western countries as well) that’s gonna be a _huge_ issue in the coming years. ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [May 13, 2004, 7:20pm UTC](https://boards.straightdope.com/t/did-the-rates-of-overweight-people-double-since-1990-because-the-bmi-changed/244826/9 "2004-05-13T19:20:45Z")
Changing the BMI clearly made more people overweight. On the other hand, people have clearly become fatter since 1990 too. No doubt hundreds and thousands of people who have kept a stable body weight over the years did become overweight only due to the change in BMI. However, many more did not keep a stable weight during this time and would have had a bmi greater than 27 anyway. No one thinks the BMI is a perfect tool, but the number of very muscular individuals who throw the curve off is pretty small. It is a reasonable standard for obesity due to the ease of calculation, but of course is far from the best possible standard or only measure. Just as a relatively small percentage of overweight people have a genuine untreated thyroid disorder; only a relatively small percentage of people with high BMIs have it because of many years of bodybuilding.