That depends entirely on what you think obesity is.
If you think the defining feature of obesity as a medical condition is the presence of a certain amount of body fat (e.g. greater than 20% in boys and greater than 30% in girls), then, as outlined in a systematic review and meta-analysis by Simmonds and colleagues, published in Obesity Reviews, BMI is a reasonably good measure (when compared to actual body composition as measured by densitometry (hydrostatic weighting or air displacement plethysmography), deuterium dilution, or DXA).
However, if you believe that the defining feature of obesity (in contrast to simple adiposity or fatness) should be a measure of whether or not excess or abnormal body fat actually impairs health in a given individual, then this analysis is not really helpful.
This distinction is important if we embrace the notion that obesity is a disease – a disease impairs health. A risk factor, on the other hand, is just that – a risk factor for a disease.
They are not the same.
Risk for diabetes is not diabetes.
Risk for heart disease is not heart disease.
Risk for cancer is not cancer.
Thus, the onus on anyone describing anyone as having the disease “obesity”, is to demonstrate that that person actually is “diseased” or in other words, is experiencing an impairment in health directly related to the presence of abnormal or excess body fat.
Thus, as this paper shows, BMI may well be a reasonable diagnostic measure of adiposity (more so in girls than in boys) – whether or not it helps diagnose obesity is another question entirely.
A few weeks ago, I was invited by the Editor of The Lancet Diabetes & Endocrinology to review Obesity in Canada, a collection of articles by Canadian and Australian authors, who identify themselves as “fat scholars” engaging in “critical fat studies”. (Edited by Jenny Ellison, Deborah McPhail, and Wendy Mitchinson).
Obviously, I have had multiple interactions with “fat scholars” over the years and have certainly always learnt a lot.
Indeed, I would be the first to admit that many of my own ideas about obesity, including the issue of whether or not obesity is a disease and, if so, how to define the clinical problem of obesity in a manner that does not automatically label a quarter of the population as “diseased”, has been shaped by this discourse.
Similarly, my own notions about obesity management, with a primary goal to improve health and well-being rather than simply moving numbers on the scale, are clearly influenced by ideas that first emerged from the “fat acceptance camp” (not exactly the same, but close enough).
Thus, there was certainly much in this compendium that I was already quite familiar with – which certainly made the reading of this 500 page volume most enjoyable.
Nevertheless, it is important to realise that “fat scholars” do not just see themselves as “scientists” – rather, they see the practice of “fat studies” as a political work, tightly (some might say dogmatically) bound to a frame of reference that is reminiscent of political “activism” rather than “science”.
Fat scholars (at least the ones represented in this volume) are not just critical of, but also appear most happy to discard the entire biomedical and population health discourse around obesity, as nothing more than (I paraphrase), “a thinly-veiled conspiracy by the biomedical establishment to create a moral panic that justifies the reassertion of normative identities pertaining to gender, race, class, and sexuality.”
Accordingly, some fat scholars appear to be of the rather strong opinion that there is in fact no “global obesity epidemic” and even if there are perhaps a few more fat people around today than ever before, the health consequences of obesity are vastly overblown, and any recommendations or attempts to lose weight are not only ineffective but actually harmful.
Now, before you simply roll your eyes and decide to file away the whole exercise in the drawer that you reserve for global-warming deniers and anti-vaxxers, let me assure you that there is indeed a lot to be learnt from the discourse (at least I did).
For one, there are absolutely fascinating chapters on the history of fat activism in Canada (which apparently dates back to the early 70s), enlightening perspectives on Indigenous People’s encounters with obesity, the issue of “mother blaming”, and even a chapter on fat authenticity and the pursuit of hetero-romantic love in Vancouver.
There are stories about how kids and families experience childhood obesity intervention programs and how primary school teachers themselves struggle with being thrust into a role of being role models while struggling with their own personal response to the pervasive obesity messages.
Obviously, there are some ideas that may be harder to swallow than others.
Take for e.g, the notion that the “root cause” of fat phobia (at least according to fat scholars who rely on postmodern feminism, psychoanalysis, and queer theories), is simply a reflection of the femininity ascribed to body fat: because women need fat to menstruate, body fat can be seen as female reproductive material that, in patriarchy, must be contained, restrained, and ultimately eliminated.
Personally, I can no doubt think of a wide range of other “root causes” that would result in “fat phobia” and “weight stigma” without having to quite delve into feminism or queer theories – but that’s another story.
Or the notion that there is in fact no link between body fat and diabetes – something that is easily refuted by a host of experimental animal studies and clinical observations (which, in the world of “fat scholars” do not appear to exist or are for some opaque reason deemed entirely irrelevant for the discourse).
Nevertheless, these “peculiarities” aside, I do admit that I found the book a very timely, relevant and enlightening read for anyone who is seriously interested in the issue of obesity and bold enough to step out beyond the typical biomedical discourse.
I would most certainly recommend this volume to people working in health policy and public health but also to clinicians, who seek to better understand some of the social aspects of the obesity discourse as it relates to their patients.
There is much in the volume that I perhaps disagree with or rather, see from a different perspective (I am after all a clinician) – however, openness to entertaining alternative views and ideas, and willingness to shift your own opinion and beliefs when new evidence emerges, is the defining characteristic of good scholarship – and I certainly remain a lifelong student.
Disclaimer: I was given a complimentary copy of Obesity in Canada to review by the Lancet Diabetes & Endocrinology
Continuing in my miniseries on the recent “Clinical Discussion” on obesity, published in the New England Journal of Medicine, I now turn to the second question that we need to answer before jumping into giving our patient any advice about managing her weight.
The first question, as discussed in yesterday’s post, is to understand the possible “root-causes” of her weight gain, as these may not only have to be targeted during treatment but can also pose important barriers to management (e.g. emotional eating, depression, lack of time, stress, etc.).
Unfortunately, as I noted yesterday, the case presentation did not provide much in terms of helping us understand, why this patient has a BMI of 32 in the first place.
Not only did we not get any information regarding her weight trajectory, we were also only told that she eats out often and is largely sedentary – not really much to go on, given that the same could be said about the vast majority of people living in the US (or in Canada), irrespective of their size or weight.
As for the second question that we now need to answer, before giving any advice, is whether or not she even has a health issue that needs to be addressed.
Thus, while we may be led to believe that her BMI of 32 in itself justifies the diagnosis of “obesity”, we must remember that BMI is a essentially a measure of body size, in fact, not much better than a dress size.
Although statistical risk for certain health problems (e.g. diabetes, hypertension, joint problems, sleep apnea, etc.) may rise with increasing BMI, this relationship is far weaker than most people think.
Indeed, as we have previously noted, as many as 25-30% of individuals in the BMI 30-35 range may have no clinically significant health impairments whatsoever. This is particularly true for younger individuals and for women – out patient just happens to be a 29 year-old female.
Thus, it is in fact not all that surprising, that the case report goes on to note that Ms Chatham has neither a history of coronary artery disease nor diabetes (which would indeed be rather unusual if did), and, apart from a marginally elevated blood-pressure, her health status is largely “unremarkable”. Although not mentioned in the case vignette, we can perhaps also assume that all her lab values are normal.
Thus, even if we assume that the blood pressure reading is reliable, this information would at best put her at an Edmonton Obesity Stage 1, a stage where her long-term mortality risk would be almost indistinguishable from “normal”.
And, if we apply the actual WHO definition of obesity (the presence of excess or abnormal body fat that impairs health), we may in fact have to bend over backwards to diagnose this woman as having obesity at all.
So if there is no relevant health impairment from her BMI of 32, why is she even concerned about her weight?
Because, as we learn from the case study, she has been told indirectly, by her friends and family, that she is “overweight.”
Which brings me back to our question at hand: does this woman even have a health problem that needs to be addressed?
My answer would be a rather enthusiastic, “not really”.
We could of course leave it at that, and simply reassure her that she is pretty healthy (although she may perhaps want to have her blood pressure rechecked in the near future).
If however, she does persist in her intention to lose weight, and continues to insist that we advise her on what she can do to improve her health (which are really two very different questions), we may need to have a much longer discussion with her.
This is something we will look at tomorrow, when we address the third question:
What would be the best management plan for this patient?
Yesterday, I posted about the “Clinical Discussion” of obesity management, presented to us by the venerable New England Journal of Medicine.
I wrote about how the ignorant and moralizing “opinion” of one of the discussants, devoid of even the smallest insight in to the complex sociopsychobiology of this chronic disease, is exactly the kind of “thinking” that is holding back the field (and has been for decades).
But these are not the only problems with the “Clinical Discussion”.
Rather, the problems start with the very choice and description of the “case”.
Indeed, the case warrants a careful line-by-line analysis, to reveal just how the use of the “stereotypical” depiction paints a picture of what (as we will see in a later post), could well turn out to be a much more complicated case than either of the discussants acknowledge.
As we are told,
Ms. Chatham is a 29-year-old woman who recently joined your practice; this is her second visit to your clinic.
In other words, this is a young woman, whose life you know virtually nothing about, not that this should ever stop you from stating your sound medical opinion.
She made today’s appointment to discuss how she can lose weight and whether there are medications that she can take to aid in weight loss.
In other words, a typical “fat” patient looking for a “quick fix” via “diet pills”?
She is relatively healthy, except for a history of childhood asthma.
Did the asthma play any role in her weight gain? Did it limit her physical activity as a kid? Was she on anti-allergic drugs or even systemic steroids that may have led to weight gain? Your guess is as good as mine.
She says that she has been told indirectly, by her friends and family, that she is “overweight.”
Because, obviously, she does not own a mirror, never shops for clothes, and has probably never given her shape or size a second thought, and therefore, needs to be “told” by the good people around her (and perhaps on occasion by perfect strangers she may just happen to meet on the street), that she has a serious health problem and needs to urgently see a doctor.
She has tried several popular diets without success; each time, she has lost 4.5 to 6.8 kg (10 to 15 lb) but has been unable to maintain the weight loss for more than a few months.
Which, I’m guessing, simply goes to prove her lack of motivation and effort. Obviously, like most “fat” people, she is just too weak-willed to maintain weight loss and apparently always gives up far too soon. Never mind, that this is exactly what happens to 95% of people (skinny or fat) who lose weight and never mind, that (as some of us now realise) there is in fact a complex neurohormonal physiology, which tightly regulates body weight and is there solely for the purpose of effectively “defending” against weight loss.
She does not have a history of coronary artery disease or diabetes.
Which would in fact be surprising, given that she is a 29 year-old woman!
She has a regular menstrual cycle.
Which means what exactly? Are we supposed to rule out PCOS or fertility issues based on this clinical “pearl”?
She does not take any medications or nonprescription supplements.
So at least we know that she cannot simply blame her weight gain on any current medications.
She does not smoke but does drink alcohol, occasionally as many as 4 or 5 drinks in a week, when she is out with friends.
Which you could also say about millions of other people (including myself), irrespective of their BMI or health status – it’s what people do!
She tells you that she “watches what she puts in her mouth”…
Which, of course we should have a hard time believing, because as we all know, “fat” people are habitual liars when it comes to what they “tell” us about their diets.
…and reads the nutritional labels on food packaging.
or, at least that’s what she “tells” us – you’re welcome to believe her or not.
However, she enjoys eating out and orders take-out meals 8 to 12 times a week.
Wow! Here we have a “fat” person who actually “enjoys” eating out – as many times as (hold your breath) once or twice a day – and that, despite claiming to read food labels! Never mind that this is exactly how 99.9% of the US population happens to eat (no matter what their size or health status) – clearly, this irresponsible behaviour must change if there is to be any hope for her!
She works as a computer programmer and spends most of her day sitting in an office.
There we have it – typical “sedentariness” a well-known “cause” of obesity (or so we are told), because (as should be obvious to anyone who understands the complexity of energy homeostasis), all people who sit in offices (not to mention the now immortalised 400 lb “hacker”), struggle with their weight.
She belongs to a fitness club and tries to go there about once a week but notes that her attendance is inconsistent.
Because, of course, it’s typically the fat people with gym memberships, who never show up for training. Also relevant, because most of us continue to believe that exercise is the best way to lose weight.
On physical examination, her vital signs are unremarkable except for a blood-pressure measurement of 144/81 mm Hg.
Which we must obviously assume to be reliable, as the docs have certainly ruled out the presence of “White-Coat” hypertension and bothered to ensure that they are indeed using an appropriate cuff size.
She is 1.7 m (5 ft 7 in.) tall and weighs 92 kg (203 lb), and her body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) is 32.
Which contains about as much clinically valuable information as telling us that she is a size 16.
Her waist circumference is 94 cm (37 in.).
Another piece of useless information, especially in an otherwise healthy woman.
There is no peripheral edema.
Which, I guess, clearly tells us that she can forget about using “fluid retention” as an “excuse” for her weight.
The rest of the examination is unremarkable.
There you have it – with this information in hand, we are now clearly poised to give her meaningful clinical advice to help her better manage her weight.
What surprises me about this (apparently “typical”) case history, is that the editors of the New England Journal of Medicine, otherwise so concerned with brevity, did not simply decide to shorten the “case” to the following:
“Ms. Chatham is a pretty healthy 29-year-old working woman, who happens to live in the USA.”
That one line would in fact contain about all of the information we now have about Ms. Chatham, the difference being, that this statement is actually better, in that it is elegantly crafted to avoid the use of “stereotypical” fat-shaming language and imagery.
Furthermore, this sentence, quite like the “case”, is also void of any indication of the actual complexity that even “simple obesity” can present in clinical practice (which, I perhaps mistakenly, assumed would have been the whole point of the Clinical Discussion in the first place).
Is anyone curious as to the information that I would really liked to have about Ms. Chatham to come up with advice that would actual help her?
Then, please stay tuned for tomorrow’s post.
While many folks have no problem seeing how “excess” body fat can often lead to health problems, they may wonder what exactly is meant by “abnormal” body fat and are perhaps unsure as to why this would be included in the definition of obesity.
This is where we need to take a moment to remind ourselves that fat tissue is actually a vital organ, without which, we would experiences all kinds of health problems. Not only, is our ability to store excess calories vital to prepare for the next major illness or famine, it is also a vital organ for reproduction (women stop having periods when their fat stores get too low).
That said, the safest place to store all those excess calories is in your fat tissue, especially the fat tissue directly underneath your skin. This is where the excess calories cause the least trouble, not affecting the functioning of other organs or clogging up your blood stream, and where they can sit for decades, until they are perhaps one-day called upon in a time of need.
It is also “normal” to have a small amount of fat in other depots such as around the gastrointestinal tract, the heart, or the kidneys – here the fat serves both a mechanical and immunological function – again, the fat here generally does not cause any health problems (indeed, lack of fat in these locations may).
All of this is not very interesting from a medical or health perspective, as this kind of fat generally does not cause any real health problems, unless, it perhaps expands to a size that causes mechanical issues simply due to its sheer mass.
In contrast, the term “abnormal” refers to fat accumulation in parts of the body where you would not normally find fat in a “healthy” person. This, is commonly referred to as “ectopic” fat and refers to fat accumulation within organs like the liver, pancreas, heart, skeletal muscle or other organs, where you would rather not have any fat.
These “abnormal” fat accumulations can substantially disrupt organ function, leading to all kinds of metabolic problems.
Interestingly enough, there is not a very strong relationship between the total amount of body fat and the location of that body fat.
The extreme example of this is seen in patients with lipodystrophy, who, being unable to store excess calories in “normal” subcutaneous fat depots, deposit their fat in the liver and other organs, thus presenting with all of the problems generally associated with obesity.
Exactly why some people are more prone to “ectopic” fat deposition that others, who can apparently tuck away all their extra calories underneath their skin with little, if any, impact on their health, remains largely unknown, except that genetics appears to play a very substantial role.
But, whatever the reason, the bottom line remains that even very little extra body fat, if stored in the wrong location, can cause all of the metabolic problems generally associated with obesity.
In contrast, even large amounts of body fat, if safely sequestered away in subcutaneous depots may have little (if any) impact on health.
This is why the WHO included both the presence of “excess” as well “abnormal” body fat in their definition of obesity.
Again, none of this can be measured by stepping on a scale or looking at a BMI chart.
If your excess or abnormal body fat affects your health – you have obesity – if it doesn’t, you don’t.