Straw Man

Straw Man Arguments about Obesity and BMI

We occasionally hear from folks who find the notion that obesity is a disease to be quite offensive. In support of this perspective, the argument is that obesity cannot be a disease because everybody knows obesity is simply a label for having a high BMI. In other words, obesity is just a word used to pathologize people who are living in large bodies, based solely upon their body weight. In our view, this is a straw man argument based on a false definition of obesity.

Public Understanding of What Obesity IsIt turns out that everybody doesn’t agree obesity is simply a matter of having a high BMI. Ask the general public whether obesity is defined by a high weight or an unhealthy accumulation of fat tissue and you will find that they are closely divided on the question.

If you ask medical experts, it’s pretty clear that they do not define obesity based on body weight.

The American Association of Clinical Endocrinologists defines obesity as a “disease with impairment of normal functioning including appetite dysregulation, abnormal energy balance, endocrine dysfunction including elevated leptin levels and insulin resistance, infertility, dysregulated adipokine signaling, abnormal endothelial function, and blood pressure elevation, nonalcoholic fatty liver disease, dyslipidemia, and systemic and adipose tissue inflammation.”

BMI, they say, “is a proxy for the relative quantity of adiposity and is used to predict and evaluate disease risk.”

The Endocrine Society says “Obesity is a chronic (long-term) medical problem of having too much body fat.”

The Obesity Medicine Association states that “obesity is defined as a chronic, relapsing, multi-factorial, neurobehavioral disease, wherein an increase in body fat promotes adipose tissue dysfunction and abnormal fat mass physical forces, resulting in adverse metabolic, biomechanical, and psychosocial health consequences.”

The Obesity Society simply says that “obesity is defined as excess adipose tissue.”

The American Medical Association defined obesity in 2013 by saying, “Obesity is a multi-metabolic and hormonal disease state including impaired functioning of appetite dysregulation, abnormal energy balanced, endocrine dysfunction including elevated leptin levels and insulin resistance, infertility, dysregulated adipokine signaling, abnormal endothelial function and blood pressure elevation, nonalcoholic fatty liver disease, dyslipidemia, and systemic and adipose tissue inflammation.”

CDC states that “BMI can be used as a screening tool but is not diagnostic of the body fatness or health of an individual.”

The American Heart Association says “Obesity is defined simply as too much body fat.”

So obesity is a personal health condition of metabolic dysfunction arising from excess visceral fat that sets up a cascade of other chronic health problems. It can happen in people with relatively low BMI who have visceral adipose tissue producing the symptoms of obesity. Someone with a high BMI can be metabolically healthy. Obesity that’s been successfully treated might still leave a person with a BMI above 30.

Far too many people make assumptions about obesity based on appearances. Such assumptions, unfortunately, are promoted by obesity awareness campaigns that do more harm than good.

BMI is a useful screening tool. It’s been used as an indicator for the severity of obesity. But it should not be confused with an actual diagnosis of obesity.

Straw Man, photograph © Clyde Robinson / flickr

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March 12, 2016

6 Responses to “Straw Man Arguments about Obesity and BMI”

  1. March 12, 2016 at 9:56 am, Angela Meadows said:

    A high BMI or too much body fat? That is really splitting hairs Ted. Click on many of those links (I don’t have time to click on all of them), and they say obesity is having an excess of body fat. How do you know if you have too much? Well a good way is to see if your BMI is over 30. Then you fall in the obese category. And of course, ‘obesity’ affects one-third of Americans. Whether you are measuring body fat %, BMI, or whatever, this is all ‘body shape by any other name.

    If I have understood you correctly in the past, you content that problematic weight is weight associated with impaired metabolic function. Is that right? I don’t have a problem with that. Although I would contend that problematic metabolic function is impaired metabolic function and leave the weight out of it. But regardless of what you *mean* when you say ‘obesity’, practically all of these institutions say it can be defined by some measure of body shape or composition.

  2. March 12, 2016 at 11:05 am, Ted said:

    Thanks, Angela.

  3. March 12, 2016 at 11:58 am, Carolyn said:

    This really seems pretty ingenuous. BMI of 30 plus is the definition of obesity put forth by WHO and by the NHLBI clinical guidelines. Government and international statistics about the prevalence of obesity are all based on BMI. Numerous articles in the medical literature talk about ‘misperception’ when people who have BMIs over certain values don’t perceive themselves as obese. Given all this, it’s hard to turn around and say that BMI isn’t the ‘real definition’ but rather some undefined metabolic function measurements. Historically obesity meant excess body fat, but there is no real definition of what level that means (or why) even though some people use arbitrary cutoffs. Now ‘obesity’ is shading toward metabolic dysfunction, allowing people to be obese at any level of BMI or body fatness. What do we really mean? And what is the prevalence of obesity then?

  4. March 12, 2016 at 2:01 pm, Ted said:

    Good questions Carolyn. I’m glad you mentioned all the misguided publications that try to ascertain and then bemoan that not enough people label themselves as having obesity. It strikes me as a spectacularly unhelpful agenda to pursue.

    BMI was developed as a tool for epidemiologists to estimate the prevalence of health risks attributable to excess adiposity and the metabolic dysfunction that results from the accumulation visceral fat. If you want the latest data on the prevalence of obesity, this is a good reference: http://www.cdc.gov/nchs/data/databriefs/db219.htm

    While BMI is useful for epidemiology, it’s not very useful for diagnosing the health status of individuals. If you want to know more about the clinical assessment of obesity, I would suggest reading up on the EOSS here: http://www.nature.com/ijo/journal/v33/n3/abs/ijo20092a.html

    If your questions are posed just to make a point, thanks for sharing them.

  5. March 13, 2016 at 1:57 pm, Carolyn said:

    My point was that If obesity isn’t defined as high BMI, then how do we know what the prevalence of ‘real’ obesity is? From a definitional point of view, all this shades off into complete confusion. It’s as if we say that “tall” meant over 6’5″, but then said that some people were ‘tall’ who were below that value, and some people who were taller than that value weren’t really “tall” after all. And then we ended up saying that some people who were ‘short’ (let’s say below 5’6″) were actually tall after all.

  6. March 13, 2016 at 2:33 pm, Ted said:

    Thanks for sharing your point of view, Carolyn.

    To answer the epidemiologic question, BMI provides a reasonable, though imperfect means for estimating obesity prevalence. For the diagnosis of an individual’s health, it is nothing more than a crude screen. The literature on this subject is massive and it continues to grow. Again, I encourage you, if you have any interest, to read more about the Edmonton Obesity Scale.