Any follower of media reports or even research papers on the relationship between obesity and mortality should be righty confused by now.
Not only are there publications suggesting that the relationship between obesity and mortality isn’t that strong after all and that perhaps the BMI levels associated with the longest survival are somewhere around 30 (and not below 25) but then there is the issue of the obesity paradox, or the finding that among people with chronic (and some acute illnesses), a higher BMI is associated with better survival than being of “normal” weight.
On the other hand, there is overwhelming evidence that higher BMI’s are associated with an increased risk of a wide range of health problems – from diabetes to cancer.
This is not to say that everyone with a higher BMI is sick – they are not! But there is no doubt that the risk of illness does increase with higher BMIs.
In our own study on the Edmonton Obesity Staging System (EOSS), which classifies individuals based on their actual health rather on their BMI, we found that while about 50% of individual in the BMI 25-30 range can be considered healthy (EOSS Stage 0 or 1), this number drops to below 15% for individuals in the BMI 40+ range.
So, if obesity is such a risk factor for disease, why do epidemiological studies struggle to consistently show an effect of obesity on mortality?
Now, a paper by Andrew Stokes and Samuel Preston, published in the Proceedings of the US National Academy of Science, suggests that it is not current weight (as used in many studies) but rather the highest lifetime weight that is most clearly associated with mortality.
Their reasoning is as follows. “Intentional” weight loss in the population is rare (very few people in the general population ever consciously manage to lose a significant amount of weight and keep it off)
In contrast, “unintentional” weight loss, when it occurs is generally a bad sign. Indeed, one of the best indicators of poor prognosis (for almost any health condition) is when someone loses weight. In many cases, this “spontaneous” weight loss can precede overt illness or death by many years.
Thus, the authors argue that most of the literature on this issue is simply confounded by the confusion caused by all the people who have unintentionally lost weight due to an underlying health problem (diagnosed or undiagnosed).
As these people would be at higher risk of death, despite measuring in at a lower weight, they muddy the waters making lower BMI levels look more dangerous (or in comparison higher BMI levels look safer) than they are.
To test their hypothesis, the researcher looked at data from the US NHANES study linked to death registers using four different approaches:
Model 1: BMI measured at the time of survey (this is the method most commonly used in epidemiological studies)
Model 2: The highest reported lifetime BMI at the time of survey
Model 3: Individuals surveyed in their current BMI class who had never been heavier compared to individuals in that BMI class who reported formerly being in a higher BMI class.
Model 4: Individuals surveyed in their current BMI class compared to people who were formerly in that BMI class but had moved to a lower BMI class by the time of the survey.
In both models 1 and 2, there was a greater risk of mortality with higher BMI class, but the relationship was stronger in model 2 (highest lifetime BMI) than in model 1 (current BMI).
In model 3, there was still an increased risk with higher BMI class but within each current BMI class, risk was higher in individuals who had previously belonged to a higher BMI class.
In model 4, mortality also rose with the highest weight achieved but was markedly higher in individuals who lost weight after achieving a particular BMI category compared to those who remained at that maximum.
These findings have important implications for our understanding of the relationship between BMI and mortality.
As the authors note,
“Confining analytic attention to survey BMI alone thus sacrifices important information provided by an individual’s maximum BMI. The poor performance of the survey-only model is especially salient because models using only BMI at survey dominate the set of findings in the literature on the relation between BMI and mortality.”
The errors in not considering highest BMI are not trivial.
“33.9% of individuals in the sample who were normal weight at survey were formerly overweight, and this group had three times the prevalence of diabetes and cardiovascular disease CVD) relative to those who were in the normal-weight category at both max and survey.”
Here is how you would interpret the data,
“Disease prevalence and mortality both rise with increases in maximum BMI and rise even further for those who reach a particular maximum BMI category and then lose weight. These patterns strongly suggest that obesity raises the risk of diabetes and CVD and that, once acquired, these diseases often precipitate weight loss….Only by using weight histories can this pattern of erasure be identified and corrected.”
The use of historical data in determining risk would not be a new concept,
“The introduction of historical data in the analysis of smoking occurred more than a half century ago, when studies began to distinguish among current-, former-, and never-smokers.”
Similarly, in the context of obesity one would need to differentiate between people who currently have obesity, people who previously had obesity, and people who never had obesity.
All of this only works, because in these type of epidemiological studies, “intentional” weight loss, be it through behaviour change, medication or surgery, is so rare as to be non-existent. Virtually all weight loss seen at a population level in “unintentional” and probably related to underlying health issues.
Thus, one should not interpret these findings to mean that someone intentionally losing weight through behavioural, medical or surgical treatments is at a higher risk for mortality – the intervention studies we have on that (this cannot be studied in population studies as there are so few cases of “treated” obesity), suggest otherwise.
For clinicians, these data point to the importance of noting the highest BMI and not just current BMI – if the patient has lost weight (especially if this is not explained by obesity treatment), then this may be a high-risk patient.
There are no doubt long-term “success stories” out there – people who just by making (often radical) changes in their diet and activity behaviours have lost a substantial amount of weight AND are keeping it off.
However, there is also no doubt that these people are rare and far between – which is exactly what makes each one of them so exceptional.
I am not speaking of all the people we hear or read about who have lost tons of weight – we hear about their spectacular weight loss – cutting carbs, cutting gluten, going vegan, going paleo, alternate day fasting, running marathons, training for iron man competitions, going on the Biggest Loser or eating at Subway.
What we don’t hear about is the same people, when they put the weight back on – which, in real life is exactly what happens to the absolutely vast majority of “losers”. We hear of their “success” and then we never hear from them again – ever.
Oprah is different! Different because, we have had the opportunity to follow her ups and downs over decades.
When Oprah “succeeds” in losing weight, she does not disappear into the night – no – she puts the weight back right in front of our eyes, again and again and again and again.
Now, comedy writer Caissie St.Onge, in a comment posted on facebook, pretty much summarizes what it is we can all learn (and should probably have learnt a long time ago) from Oprah:
“Oprah is arguably the most accomplished, admired, able person in the world. She creates magic for other people and herself on the regular. So, if Oprah can’t do permanent lifelong weight loss, maybe it can’t be done. Oprah is also crazy rich. If Oprah can’t buy permanent lifelong weight loss, maybe it can’t be bought.”
“I’m not saying you should give up on your dreams of having the body you want. I’m just asking, if you never get that waist, will your life have been a waste? (I see what I did there.) Every day we are bombarded with media, content and products. Special foods and drinks. Programs and plans. None of this shit has ever worked for Oprah and it probably isn’t gonna work for me or you.”
“I know the reason isn’t because you’re weak. If you’re carrying around 10 or 20, or 50 or 150 pounds more than the tiny friend who always calls herself fat in front of you and you don’t kick her in the back of the knee, you’re the opposite of weak. You’re very, very strong in at least two different kind of ways.”
“I realize there are people who are DYING to tell you what they think about what you should do with your body. It always starts with, “No offense but…” or “Not to be mean, but…” And it’s always offensive and mean, but also, you probably say things to yourself every day that are way meaner than what any “well-intentioned” “friend” or internet troll could come up with. You’re gonna have to try harder if you want to beat us at our own game, internet trolls. I would pop someone in the chops if they spoke to me the way I speak to myself. And I would bet all of Oprah’s money that Oprah says mean shit to herself too. Oprah does.”
“You can do what you want. You knew that. But I’m gonna stop wishing that I didn’t have dimples on the backs of my hands or that my ankles were more flattered by strappy shoes. I’m gonna stop telling people that they look great and start telling them what I really mean, that’s it’s nice to see them. And I see you. And I like you so much just how you are right now, and not a year or five years from now when you may or may not be smaller….. Oprah. I’ll love you either way.”
Cassie’s entire post is available here
This is largely, because to win a debate you need to take a biased and one-sided view of the topic and speak with conviction – at least if the intention is to sway the audience.
The problem is that presenting a radical stand-point convincingly may lead the audience to believe that this is your actual position on the matter (rather than simply a role assigned to you by the organizer).
To not fall into that trap, these debates often end up with the debaters agreeing more than disagreeing.
Case in point a debate at Obesity Week, on whether or not people with obesity who are metabolically healthy should be advised to lose weight.
The pro side was represented by Mark Hamer, who essentially made the argument that truly metabolically healthy obesity (MHO) is a rather rare phenotype and will in most cases (sooner or later) progress to unhealthy obesity (UHO), so that differentiating between the two both in clinical practice and in public health recommendations to lose weight is neither practical nor necessary.
On the con side, Sam Klein argued that on the one hand, MHO individuals appear far more resistant to developing metabolic risk factors (even with weight gain) and that weight-loss always comes with a cost and that interventions should therefore be focussed on people who stand to benefit the most, i.e. people who already have metabolic problems.
Klein also pointed out that we not be tempted to treat “hyperBMIemia” – but take the actual health of the patient into account.
In the end, as expected, the debaters came to agree on the fact that everyone could stand to benefit from improving their “lifestyles”, particularly their activity levels (which really wan’t the question that was being debated).
If nothing else, the debate revealed the ongoing conflict between population messages (every one should strive for a “healthy” weight – whatever that is) and clinical decision making, where recommendations need to be personalized to the actual risk of the individual.
Recent visitors to the Canadian Obesity Network website may have noted a few changes.
For one, a new logo has replaced the time-worn “maple leaf + measuring tape“. This is in response to strong feelings among both the board and membership that the old logo, with its measuring tape no longer represents one of CON’s key messages, namely that health is not a number on a scale or measuring tape, and that there is no consensus as to what a healthy weight is and how it would be determined for any given individual.
This is particularly a sensitive issue and a mixed message when it comes to public engagement, which brings me to the second major change on the website – a section for the general public.
Until now, despite amassing an impressive membership that is fast approach 12,000, membership and information on the CON website was targeted and reserved to people with a professional interest in obesity – researchers, health professionals, decision makers, trainees, and a range of other stakeholders.
But the most important stakeholder of all – people living obesity – were excluded – both from membership and content.
Since last week, anyone with an interest in obesity can find general information on obesity on the CON website and anyone can subscribe to a soon to be launched regular newsletter for the public, which will feature the latest in obesity research and obesity relevant resources around the country – both in prevention and management.
Currently, the website is still under construction and at this time most of the information focusses on one of CON’s main goals – to reduce obesity stigma and weight-based discrimination.
Stay tuned for sections on prevention, public health, children and youth, pregnancy and a growing catalogue of evidence-based resources for obesity prevention and management.
While you will hardly find the usual “recipes and exercise tips” that are often featured on obesity related website, you will be sure to find a growing body of obesity knowledge that informs about the prevention and management of this chronic disease.
I hope you will agree that the new logo’s sleek icon is reflective of the network’s Canadian focus, with the bottom two segments suggestive of two supportive hands, perhaps representing the many professional members of CON working to find bette ways to prevent and manage obesity. The white dot focal point on the leaf icon can perhaps be interpreted as the head of a person with uplifted arms (i.e. the white space between the three leaf sections), an expression of hope and aspirations.
To subscribe to the forthcoming public newsletter click here
To follow CON on its new Facebook page click here
To join CON as someone with a professional interest click here
This morning, I presented a keynote address at the 31st Scientific Meeting of the Deutsche Adipositas Gesellschaft (German Obesity Society) on the issue of risk stratification beyond BMI.
As regular readers will be well aware, I have long stated that our current definition of obesity based on BMI is problematic when applied to individuals presenting with excess weight.
We have therefore proposed the use of the Edmonton Obesity Staging System as a simple clinical tool for risk stratification that can guide clinical decision making.
Judging by the response from the audience, this concept met overwhelming approval, especially from the clinicians in the audience.
If, how, and when this concept will find its way into German obesity management guidelines remains to be seen.