Dr. Sharma's Obesity Notes

While I am on a brief holiday in Berlin, I thought I’d rerun a few earlier posts that discuss the issue of measuring obesity and how such measures may or may not be helpful in obesity management - as many readers may not have seen these posts before, comments are very much appreciated.

The following was first posted on July 30, 2008

Body mass index (BMI) is currently widely recommended and used as the best measure of obesity both in population and clinical studies. It dates back to the Belgian statistician Adolphe Quételet, who between 1830 and 1850 described this index as a way to characterize the level of adiposity in sedentary adults.

But how accurate is this index really to identify individuals with excess body fat?

This question was recently addressed by Abel Romero-Corral and colleagues from the Mayo Clinic, MN, USA, who analysed the relationship between BMI and body fat percent (BF%) as measured by bioelectrical impedence in 13,601 subjects (age 20-79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey (Int J Obesity).

In this study, the authors defined obesity based on the World Health Organization (WHO) reference standard for obesity of BF%>25% in men and >35% in women.

BMI-defined obesity (>=30) was present in 19% of men and 25% of women, while BF%-defined obesity was present in 44% of men and 52% of women.

A BMI>=30 had a high specificity (men=95%, women=99%), but a poor sensitivity (men=36%, women=49%) to detect BF%-defined obesity. This means that while the BMI definition does identify the vast majority of men and women who have increased body fat, it also misses a significant number of individuals who have high percent body fat and would be considered obese by the BF% definition.

The diagnostic performance of BMI diminished as age increased and in the intermediate range of BMI (25-29.9), BMI failed to discriminate between BF% and lean mass in both sexes.

The authors conclude that accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. Thus, the currently recommended BMI cutoff of >=30 kg for obesity has good specificity but misses more than half the people with excess fat.

The scary part of these results of course is in the fact that based on actual BF% the prevalence of obesity in this population doubled! On the other hand, we know that %body fat or body composition alone is not a particularly reliable measure of health.

I prefer to continue using my operational clinical definition of obesity: the presence of excess body fat that threatens or affects your health.

Given the wide variation in the inter-individual susceptibility to develop adiposity-related health problems, the diagnosis of obesity and the question of whether or not reducing the proportion of body fat will indeed benefit your health will always remain a matter of clinical judgement.

AMS
Duschesnay, Quebec

While I am on a brief holiday in Berlin, I thought I’d rerun a few earlier posts that discuss the issue of measuring obesity and how such measures may or may not be helpful in obesity management - as many readers may not have seen these posts before, comments are very much appreciated.

The following was first posted on July 28, 2008

Don’t worry - I am not going to take off on a discussion about whether obesity is a disease or “simply” a risk factor. I am also not going to discuss again obesity definitions - anthropometric or otherwise.

Today’s post is simply about an analogy that may help sharpen our clinical thinking around excess weight.

Think of someone who has an elevated plasma creatinine level (a marker of kidney failure) - the elevated creatine definitely tells us that there is something “wrong” with the kidneys, but that’s about it. From the creatine level alone we can certainly tell that the kidneys are failing in their excretory function, but we cannot tell what is causing the kidneys to fail - is it a pre-renal, intra-renal or post-renal problem? We can probably list a 100 reasons why kidneys could fail and obviously the treatment (apart from some very general principles) will very much depend on the cause, i.e. the actual diagnosis.

In many ways, one can look at excess body fat simply as a sign or symptom of the fact that there is a something “wrong” with energy homeostasis. The excess body fat tells us nothing about what the problem is - sure, it’s either excessive food intake or reduced energy expenditure - but that is like saying that the creatinine levels are elevated because the kidney is not excreting properly. I can think of a long list of reasons or factors that would contribute to excessive caloric intake or reduced energy expenditure: sociocultural factors, psychological factors, biomedical factors - figuring out what exactly is causing the energy imbalance is the real problem.

Only when we find what is causing the excessive intake will we have made a diagnosis of what is causing the problem - a few specific examples could include: poor meal planning, peer pressure, hedonic overeating, depression, obesogenic medications, binge eating disorder, defective satiety signaling, etc. The point is that till we know what is causing the overeating, we can’t fix it, which means we will have little success in treating the weight problem and will be limited to a “symptomatic” approach - just eat less!

Similarly, when the problem appears to be lack of activity, again the question is what exactly is causing the problem. Obviously if the problem is lack of time our approach will hopefully be very different than if the problem is back pain or lack of motivation (a possible symptom of sleep apnea, exhaustion or depression). A “symptomatic” but useless approach would be to simply recommend 10,000 steps. No better than offering an ice-pack to someone with a fever.

Just as the term “kidney failure” only tells us that there is something “wrong” with the kidneys the term “obesity” only tells us that there is something “wrong” with energy homeostasis.

In itself, neither the term “kidney failure” nor “obesity” is a real diagnosis - they are only helpful if they prompt further investigation into what might have or is still causing the problem. Only when we find the cause will we be on our way to solving the problem.

AMS
Edmonton, Alberta

The News Section of this week’s edition of the Canadian Medical Association Journal (CMAJ) features an article by Roger Collier, in which I am extensively quoted with regard to wether or not health professionals should use the term “obesity”.

Regular readers of these pages will be quite familiar with my views on this issu. Readers may also recall that there is indeed a medical definition of obesity and that this condition has long had its own code in the International Statistical Classification of Diseases (ICD 10 E66.0).

Here a few quotes from the CMAJ article:

Doctors are also aware that patients don’t like to be labelled as obese, even if the label is accurate. Dr. Arya Sharma, chair for cardiovascular obesity research and management at the University of Alberta in Edmonton, says he never refers to a patient as an obese individual, which implies they are defined by their condition. Instead, he will use phrases such as “person with obesity.” He also prefaces the word “obese” with “medically.”

“When you put the word ‘medically’ in front of it, it implies you are talking about a medical condition,” says Sharma, who is also the scientific director of the Canadian Obesity Network.

In a recent paper, Sharma explored historical approaches to classifying obesity. Some descriptive terms once used in medicine, he noted, were far from kind. “Although some earlier descriptions of obesity used less pejorative synonyms such as stout and corpulent (meaning excessively fat), other terms such as mammoth, monstrous and grotesque clearly reflect societal stigmatization against the obese individual and, although the stigma remains, these terms have long been abandoned,” he wrote.

Though he takes care not to offend patients, Sharma advocates for the use of the word “obesity” because it has a precise clinical definition. In fact, he was one of the few founding members of the Canadian Obesity Network who insisted the word be included in the organization’s name. Others, Sharma says, feared it would repel sponsors and harm funding, and suggested names along the lines of “The Healthy Network.”

Sharma also says the word “obesity” should be entered into medical records if a person’s BMI is 30 kg/m2 or higher. To just record the BMI, he says, would be akin to recording a patient’s blood pressure without noting the presence of hypertension.

Some health experts believe the stigma associated with certain conditions can have a positive effect, serving as a powerful motivator for people to improve their health. But when it comes to obesity, Sharma says, stigma does nothing but harm. It can deter people from seeking medical care and lead to depression, anxiety, poor body image and suicidal thoughts.

“These are concrete health risks,” says Sharma. “It’s not just about not being kind to people.”

But of course not everyone agrees with these views.

The article goes on to quote a Dr. Sally Satel, a psychiatrist and resident scholar at the American Enterprise Institute in Washington, DC, who has the following views with regard to stigma (at least in the context of addiction):

In an article titled “In Praise of Stigma,” she argued that stigma reflects a societal norm and can motivate people to change their behaviour. Though “stigma abolitionists” have good intentions, for the most part, Satel wrote that the fear of attributing blame for destructive behaviour can itself be destructive. There is much about addiction that is voluntary, she writes, and to dispel the concept of willpower will only deter the recovery process.

“There is nothing unethical — and everything natural and socially adaptive — about condemning the reckless and harmful behaviours that addicts commit,” she wrote. “This need not negate our sympathy for them or our duty to provide care.”

I would beg to argue that I yet to see any evidence in favour of the notion that societal stigma is an effective tool in getting people to live healthier. If this was true, given the widespread bias and discrimination that people with excess weight experience everyday, we should truly be a nation of rakes.

I wonder what my readers have to say about this.

For a link to the full article click here

AMS
Edmonton, Alberta

p.s. You can now also follow me and post your comments on Facebook

Sharma AM, & Kushner RF (2009). A proposed clinical staging system for obesity. International journal of obesity (2005), 33 (3), 289-95 PMID: 19188927

From time to time the media loves to write stories on the Obesity Myth.

These stories come in two flavours - the first one denies the very existence of an obesity epidemic, attributing the rise in obesity statistics to moving definitions that “suddenly” make everyone obese simply by shifting the goal post.

The second flavor of obesity myths acknowledges the increase in people with excess weight but states that carrying a few extra pounds or even having more severe obesity is not really detrimental to your health, ergo this whole obesity thing is vastly overblown.

Last week, news media around the world once again splashed Obesity Myth headlines on their front pages, this time of the second flavor - yes obesity exists, but it is really not a health risk.

These reports were based on a study by Brant Jarrett and colleagues from the Brigham Young University, Provo, UT, published in the International Journal of Obesity.

The researchers examined data from the 1988-1994, 2003-2004 and 2005-2006 US National Health & Nutrition Examination Surveys (NHANES) to determine the relationship between BMI, age, gender and current medication in 9071 women and 8880 men. Current medication (or medication loads) were considered a surrogate measure of current health status.

In both the 1988-1994 and 2003-2006 data sets, with few exceptions, medication loads did not increase significantly in overweight compared with normal-weight people, a finding that prompted the news headlines.

However, the paper did find increased medication load in people who were clinically obese (BMI>30), especially if they were 40 years of age or older.

In fact, the authors themselves conclude:

“Although obesity does not substantially affect current health in young people, it is likely that the increased medication loads in obese compared with normal-weight older people originates at least in part from an increased BMI starting at a younger age. Thus, age, gender and onset of high BMI all require consideration when using BMI to assess current health status.“

Given these findings, one can only wonder why the media chose to propagate the Obesity Myth based on this study, given that the authors themselves clearly found a relationship between excess weight and health status.

While the authors do emphasize that BMI is not a good measure of health risk, this is nothing new.

Regular readers of these pages will recall several previous posts on the limitations of BMI as an indicator of health and it were indeed these limitations that prompted us to develop the Edmonton Obesity Staging System as a more clinically relevant measure of obesity.

So, while moderate excess weight may not cause apparent health problems in the young, obesity remains a significant risk factor for poor health in middle-aged adults.

AMS
Vancouver, BC

Jarrett B, Bloch GJ, Bennett D, Bleazard B, & Hedges D (2010). The influence of body mass index, age and gender on current illness: a cross-sectional study. International journal of obesity (2005), 34 (3), 429-36 PMID: 20010903

In most countries the ratio of obesity between men and women is approximately equal. Yet, the clients in most obesity clinics and weight loss centres are mainly women.

So what is with the guys?

This question was now examined by Jane deVille-Almond and colleagues from the UK in a paper just published online in the American Journal of Men’s Health.

For this study, 266 male drivers were randomly recruited from motorway service stations and asked about body weight perception and awareness of the relation between adiposity and diabetes as well as weight loss attempts.

The median age of participants was 52 years, and 46% were obese based on BMI and 73% based on waist circumference.

Of participants with normal BMI, 18% thought they were overweight, whereas 26% of overweight participants thought they were “just right” and only 19% of obese participants recognized their obesity.

Based on WC, 30% of participants with normal waist circumference thought they were obese and 9% of obese participants realized they were obese.

Only 25% and 42% of participants recognized that diabetes is associated with large waistlies and obesity, respectively.

A total of 81% of overweight and 62% of obese participants (based on BMI) believed that they were not at increased risk of diabetes.

Perhaps not surprisingly, self-perception of adiposity in men was only a weak predictor weight loss attempts.

I guess a lot more has to be done to bring obesity awareness to menfolk’s attention - especially given that their risk for metabolic complications and early infarcts associated with excess weight is as high if not higher than that of women.

AMS
Edmonoton, Alberta

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Deville-Almond J, Tahrani AA, Grant J, Gray M, Thomas GN, & Taheri S (2010). Awareness of Obesity and Diabetes: A Survey of a Subset of British Male Drivers. American journal of men’s health PMID: 20413385