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Hey everyone, it's Mikki here. You're listening to Mini Mikkipedia and today I want to chat about BMI. So I've already recorded a podcast talking about it in the context of ideal body weight. know, like should we use BMI as a measure? mean, spoiler alert, no one really thinks you should. And I gave plenty of other parameters or measures which are much more useful at that individual level. But it is a measure that's used to describe

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population basis of obesity and not just obesity because it's more about excess adipose tissue and a shift in how we think about obesity, which came about this year and was described in the Lancet Diabetes and Endocrinology Commission, is a new framework that redefines and supports obesity as a chronic systemic condition rather than merely an upstream risk factor. So it's not merely the presence of excess body fat,

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which is the issue, it is how this sort of is integrated and complicates disease risk actually. And so it is also the presence of other metabolic health issues, which ultimately at the end of the day, this is why it matters. It's not that we should rally against anyone that's carrying excess body fat. It is when that excess body fat places that person at an increased risk of other chronic conditions, that's where we need to be concerned. Not just for the individual, but the

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others around them, the cost on the public health system, the reduction of quality of life, the shift in productivity at work when they're unable to work as well or they're off sick, you know, all of these factors. yes, it's a concern of the individual, but it has these systemic and societal issues as well, which I think is really important to acknowledge. And a paper came out actually, and it was published online in June 16, and it just talks about the

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prevalence of clinical obesity versus BMI-defined obesity among US adults. So it's looking at a measure of obesity that considers that sort clinical outcome. And until recently, the identification of obesity was based solely on body mass index, BMI, which, just to remind you, the WHO criteria, an obesity is defined as a BMI of 30 kilograms per meter squared or higher, and is further categorized as

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Class 1, 30-34.9 and Class 2, 35-39.9 and Class 3, over 40 kg per meter squared. although BMI is a widely used measurement and surrogate for fat mass, this paper points out it doesn't account for that complexity of the distribution of obesity. so critics argue that BMI isn't sensitive enough in defining obesity and can overlook underlying metabolic

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experiments associated with their adiposity. Because some individuals who have elevated BMI don't exhibit any apparent illness. you know, potentially this is because of some of those fundamental issues that BMI have. Like BMI is merely weight divided by height squared in meters. And it does not account for body composition. So you can get an entire rugby team as being classified with obesity, maybe even class one or class two obesity. Yet of course these

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individuals that's not excess adiposity at play there, that is a huge amount of muscle mass on their frame. And this is often the context with which I talk to people about with all my athletes about who do carry excess body fat as to why BMI isn't like a sensitive enough marker, but then the opposite is true as well. So whilst there can be some people who may have a BMI that categorizes them with class one, class two, or class three,

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obesity, there are also people who may be, for example, of a normal weight between 18.5 to 24.9 in terms of their BMI classification, yet could have that sort of metabolic underpinning of disease, which is where this paper is sort of coming from. So that Lancet's Diabetes and Endocrinology Commission, their new framework

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As I said, redefines and supports obesity as a chronic systemic condition rather than merely that upstream risk factor. And one motivation behind this shift away from just BMI alone, and one motivation behind this was to shift that focus just from BMI to a more nuanced assessment of adiposity in emphasizing the associated downstream adverse health outcomes. So the commission introduced two key obesity groups, preclinical obesity, characterized by excess adiposity without current

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organ dysfunction or limitations of daily activities, but with an increased risk of future disease and clinical obesity, where excess adiposity has already resulted in measurable organ dysfunction or limitations in daily activities. And what I will say is you can look in the literature, and this is where some of the narrative around a healthy body at any size comes from, is that if you have people who may be categorized with

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obesity or carrying excess body fat yet are perfectly healthy, that you can see this in sort of younger or even up to midlife, particularly if someone is active. But what we know from athlete data and what we also know just looking at population data is that over time, whatever is protecting them from adverse health outcomes at that point in time, that protection diminishes over time and they can end up in that same metabolic condition as someone who already has these

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health issues. It's a pretty significant redefinition if we want to think about clinical obesity versus BMI defined obesity. And what the authors of this cohort study did was estimate the prevalence of preclinical and clinical obesity based on a large and diverse data set. And this is from a research program called the All of Us AOU research program. And essentially the data

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used from this cohort or the data collected from this cohort is height, weight, and both waist and hip circumference. And they did that following standardized protocols. They looked at waist to hip ratio and waist to height ratio. And participants were classified as having obesity if they had a BMI equal to or over 30 kilograms per meter squared, that standard definition.

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in combination with at least one other measure of excess adiposity. And I did speak about this in my podcast about ideal body weight. So that is looking at either a waist circumference over 88 centimeters for women, over 102 centimeters for men, a waist to hip ratio over 0.85 for women or 0.9 for men. I have my issues with waist to height with waist hip ratio, as you know, or a waist to height ratio that is greater than 0.5 for all.

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or if they had two or more measures of excess adiposity in the absence of a BMI equal or greater to the standard 30. So you've got two groups there. You've got the group that has the BMI with those other excess adiposity markers, one of them, or you had a BMI that might have been categorized as normal weight, but you've got both of those waist to hip ratio or waist to height ratio is putting them at that excess risk.

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It's noted that a BMI equal or greater to 40 qualified as obesity regardless of those anthropometric measures. Clinical obesity is also further defined by presence of obesity-related symptoms or conditions or by limitations in physical function. So the cohort used was really large. It was close to 249,000 participants. The mean age of the cohort was around 51.9 years. We had 60 % were female.

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and around 52 % were white or Caucasian. And in total, 32 % of participants were considered of healthy weight, having no obesity. 28.9 % had preclinical obesity and 39 % had clinical obesity. So guys, this is close to 68 % were categorized as obese. That is a huge number of the population. After adjusting for

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of sex distribution and performing some additional age standardization. In fact, they found the prevalence of preclinical obesity was 29 % and that of clinical obesity was 35.5%. So just to remind you, preclinical obesity was excess adiposity without current organ dysfunction, but at an increased risk.

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clinical obesity had that excess adiposity with that organ dysfunction or physical limitations. So what is super interesting here, I think, is looking at the difference between BMI versus the new definition that has been proposed. And there definitely is a mismatch. What this data set found was that one in five people with quote unquote a normal BMI were reclassified as obese, either preclinical or clinical. About two thirds of the people who were over

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who had overweight BMI fell into that preclinical or clinical obesity, and nearly one third of clinical obesity cases had a BMI in the normal or overweight range. Which is, you know, this tells us that that typical BMI measure, we talk about it a lot in the context of fat loss saying that it's not a very good marker, it doesn't take into consideration muscle mass, but for the general population, most of the people who are sedentary or overweight, it's not great, but for the opposite reason, it does miss people who

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are at this increased health risk. And I think that that's super important. So the BMI alone is inadequate for identifying these at risk individuals, but the new definition can capture people overlooked by BMI. It better distinguishes between high muscle mass versus unhealthy fat mass in the overweight group. And this could potentially help us determine who is at risk and who is requiring intervention and

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who potentially isn't but this is i guess we the question remains like that is the overall goal and the potential for it to impact clinical practice health policy resource allocation is that sort of important question whether or not it does is of course a different story now there are some limitations and things which which are super important here that need to be considered the first one is that it is reliance on.

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electronic health record data. So this could introduce some bias due to disparities in healthcare access, potentially underestimating the overall prevalence and skewing estimates for certain subpopulations. So that's one thing to be mindful of. And there's no imaging data either. So this could also lead to underreporting of obesity prevalence by preventing direct measurement of body fat content. So, and that's an independent criterion in the new definition.

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And also there was a short follow-up period and a non-representative nature of the All of Us data set could affect generalizability despite the fact that there were close to quarter of a million people in there. So we can't really look at sort of the temporality of this onset of obesity and clinical diagnosis, but oftentimes it's very rare that a health condition leads to obesity in the context of how we're talking about it. This is the argument made by the authors. So does the

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few other points. the authors say, and I thought this was super interesting that, you know, their findings from this large cohort are the first to describe the prevalence of both preclinical and clinical obesity in the US. And that's what really matters. Like what level of obesity is going to lead to these sort of metabolic outcomes. Over two thirds of the individuals had obesity and among them, 57.5%. So over half of them had

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clinical obesity, not preclinical. And was more prevalent, as we often see, Black and Hispanic individuals, those who were older reported lower income and lower education attainment. And these findings are important for clinicians, clinical guidelines, healthcare systems, and policymakers, because this is how we define and allocate resources as to how to help people at that population level. Now, the difference, the WHO criteria for obesity have

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long been held the standard in research and clinical settings. And according to the 2021 to 2023 NHANES National Health and Nutrition Examinations Survey, 40.3 % of US adults had obesity as defined by the WHO. But using this definition, projections indicate that by 2030, 48.9 % of US adult population will have obesity with a quarter experiencing that sort of severe obesity above 35%.

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kilograms per meter squared. However, using this new definition, they observed a higher prevalence of obesity. Further, they found a substantial prevalence of preclinical and clinical obesity among WHO categories that do not qualify as obesity. So this does call particular attention to evaluating the metabolic health of individuals previously classified as having overweight or normal weight. And that is super important because

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It isn't just that presence of excess body fat, which creates issues. And in fact, that's just a small piece of the puzzle. There are people who may be falsely lulled into thinking they're okay and their doctors think they're okay, who are at risk of, or who are experiencing that metabolic disease. And with the increasing rates of metabolic associated fatty liver disease, of type two diabetes, these are the things which really are creating

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health issues for people as we age. So yeah, I thought that was super interesting. I really enjoyed reading the paper and just having a think about how we classify individuals and importantly, how we do it in a way that is meaningful for the overall sort of outcomes. You you're not just going to your doctor's office and jumping on the scales and they're classifying you as obese, they're using other markers and other measures to establish your overall risk. Because that is how we are able to

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Implement strategies that really sort of move the needle on metabolic health, which is super important Anyway team pop a link to this in the show notes, of course, you can catch me over on Instagram @mikkiwilliden that's where I am on threads and X as well Facebook @mikkiwillidennutrition or head to my website mikkiwilliden.com and Book a one-on-one call with me. All right team. You have the best week. See you later