Hi everyone, I'm Dr Robert Eckel. I'm a retired emeritus professor in the Department of Medicine at the University of Colorado Medical Campus, and I've had joint appointments in endocrinology and in cardiology. And I kind of represent this whole area that confers the interaction between metabolic diseases, such as obesity, diabetes and cardiovascular disease.

What are the limitations of using BMI-based measures alone to measure obesity at an individual level?

BMI is useful, it should not be dismissed clinically and does give one an idea as to whether they might in fact have too much body fat, but BMI does not measure body composition. It simply gives us some information in relationship to how our weight and height relate to one another that has some predictability of excess body fat or normal body fat but is not a direct measurement of body fatness.

So ultimately, we need better ways to go about assessing people's body fat content, which is what obesity is. Obesity is not simply a higher BMI or no obesity is a normal BMI. It in fact represents simply an estimate of what body fat may be. And one of the goals of the Commission was actually to work in ways that we can better define body fat to really get around this issue of inaccurate diagnosis clinically.

As an example, Mike Tyson, who's a world famous boxer, has a BMI of 31.6, and he would be considered obese. But Mike Tyson's body fat content is around 10%, which is clearly normal, if on the low end, for a man his age and weight. So this is an example where in fact, in many other circumstances, particularly in that gray zone of BMIs between 25 and 30, we can't really tell whether someone has too much body fat or their body composition is perfectly normal.

Can you describe the process through which the Commission reached a consensus on a new definition of clinical obesity?

That's a good question. The Commission really involved 56 people from around the world who had various expertise in obesity science and medicine. So the process we utilized was developed a series of statements, and then beyond the statements, we had to have a tremendous consensus on those statements in terms of including them in the report that followed.

So there were 82 statements, and all 82 statements had a consensus above 90%. And in fact, in 60% of those statements it was unanimous. And when in fact it wasn't unanimous, it was above 90%. So this is a process called the Delphi process, which has been utilized for decades now to reach a consensus or near consensus on issues related to science and medicine and even beyond science and medicine. So using this well honoured process to really come up with statements that we felt were well justified scientifically, the Delphi process served that tool extremely well for the Commission.

How does the Commission define preclinical obesity differently from clinical obesity?

Well, this was one of the important conclusions of the consensus process. We were called on by the Commission to really look at how we should define obesity. And the concept came across that not everyone with obesity has a disease, and in fact, one thing we wanted to dispel is causing calling obesity a disease. In some circumstances, excess body fat does result in disease. But ultimately, this definition that we've defined of preclinical obesity versus clinical obesity relates to when people have excess body fat.

I should pause there for a moment because excess body fat cannot be determined by BMI alone. Ultimately, we think that a waist circumference is a good way, clinically and very, very quickly applied in the clinic to assess whether someone has too much body fat. In fact, the waist circumference that is expanded beyond certain criteria defines excess body fat. And we know when excess body fat is contained within the abdominal cavity or around the waist that clinical obesity is much more likely. So measuring waist circumference, or doing a weight height ratio, or sometimes using a scanning technique such as DEXA, can define, first of all whether someone has too much body fat.

Now, in those people that have too much body fat, people we call preclinical obesity, in fact, have too much body fat, and they may be at risk to develop clinical obesity. But in terms of their lifestyle, and also in answer to a series of questions that relate to how obesity can confer illness or disease to follow, all of those questions are answered negatively. In other words, there's no evidence by the history or the physical examination, or in fact, biochemical measurements were done in the laboratory to indicate that people have a disease we call obesity. And again, we're dismissing the term obesity as a disease. So preclinical obesity is simply a lifestyle associated with too much body fat.

Now, clinical obesity is when the amount of excess body fat can confer illness or diseases to follow. And this could be in joints, it could be obstructive sleep apnea, it could be in the metabolic triad of having high triglycerides, low HDL cholesterol, or glucose intolerance. Or it can occur in a wide variety of other areas in terms of the reproductive system, the GU system, shortness of breath, heart failure, both HFpEF and HFrEF, etc. So these conditions have been outlined in detail, and we've listed 18 different organ systems which can impact the adult in terms of clinical obesity. And in children and adolescents, 13 organ systems that can impact the definition of clinical obesity in children and adolescents.

So this is kind of a labored answer to your very straightforward question, but it's up to the clinician, she or he, to define whether the patient who has excess body fat, measured by these methods I just described, fits into the criteria of having preclinical obesity versus clinical obesity. And the treatments to follow differ in terms of those diagnostic criteria.

What is the Commission’s stance on public health strategies for obesity prevention?

Well, the Commission was not asked to really address the public health problem of obesity and that's substantial. Currently, it's estimated in the next 10 years that 1.6 billion people globally will in fact be defined as being obese based on the BMI. Now, of course, these new criteria have not been applied, but I think ultimately the public health problem of excess body fat is something that is a tremendous challenge to really implement. And I think we need people who think outside of the box in terms of dealing with how we modify health from a public health perspective.

I always cite the example for tobacco use. In the United States in the mid-1950s, 50% of adults in the US smoked. That data in the most recent 12 months is down to 12%. Now 12% of people smoking is still too many people smoking, but yet it's taken 70 years to get from a 50% prevalence in the 1950s down to 12% in the year 2024.

So thinking about tobacco in terms of a challenge, people don't have to smoke, but people do have to eat. And so when we're thinking about the challenge of modifying lifestyle, which is impacted by so many environmental factors and in terms of the cost of food, in terms of socioeconomic issues, in terms of disparities that relate to race and beyond, all the things that really play a major role in why certain populations are more likely to develop clinical obesity, more or less preclinical obesity. And I think we really have to turn to people who think out of the box in a public health perspective, beyond what us medical and scientific people who are part of the Commission had to deal with in terms of the task that was put before us.

How should this new definition of clinical obesity affect disease diagnosis, clinical decision-making and patient care?

Well, that's an excellent question. This distinction of preclinical obesity and clinical obesity really demands a response by the clinical people who are dealing with excess body fat. Now in preclinical obesity, and I should mention that the task before us was not dealing with the therapeutics or the treatment of too much body fat, the task was to redefine obesity. And we've again come up with a diagnosis of preclinical obesity, where in fact no health problems are currently evident, or clinical obesity, where in fact the excess body fat has resulted in illness or disease. So in people with preclinical obesity, we've developed a range of risk, and that range of risk really relates to when people have higher risk versus lower risk. And that is not BMI dependent — it's related to, ultimately, things that really relate to a preclinical diagnosis.

Now, a good example there might be the concept of prediabetes. Now, prediabetes, or ultimately tendency to develop diabetes, is diagnosed by a hemoglobin A1C. So let's say we have a patient who has preclinical obesity and their hemoglobin A1C is 6.3 or 6.4, using the diagnostic criteria of 5.7 to 6.5, defining someone as having prediabetes. Now, when someone has a A1C of 6.3 or 6.4 versus 5.8, I think the emphasis should be therapeutic. That patient needs to lose weight, become more active and have a modified diet, and perhaps even be a candidate for drug therapy to modify their risk for developing diabetes or clinical obesity.

We should pause there because diabetes itself can occur in people that don't have preclinical obesity because of excess body fat. So diabetes is not listed as a diagnostic criteria for clinical obesity. You must have the metabolic triad, hypertriglyceridemia, low levels of HDL and diabetes, and those people we know are insulin resistant. So we think that metabolic triad is clinical obesity. But in fact, if you just have glucose intolerance, we're calling those people preclinical obesity if they have prediabetes. And even if they don't develop diabetes and don't have high triglycerides or low HDL cholesterol, we don't consider that clinical obesity. But again, if the A1C is closer to 6.5, we recommend weight reduction. But if the risk is low, we might encourage weight reduction, or certainly prevent additional weight reduction so that they don't approach levels of ultimately excess body fat, or in terms of the diagnosis of clinical obesity is apparent.

Now, when the diagnosis of clinical obesity is there, again 18 organ systems in adults, 13 organ systems in children and adolescents, then therapeutic decision making is essential. We want to reduce body fat in hopes that the illness related to excess body fat can be favorably modified by losing weight. And there pharmacological therapy would be much more common. And based on the extent of the illness and ultimately the degree of excess body fat, a surgical intervention might be a consideration clinically.

But I remind the audience that the task we had was not therapeutic decision making. I think of these 56 commissioners from all over the world — everyone was capable of making clinical decisions based on the diagnosis of preclinical obesity versus clinical obesity, but again, that was not the goal of the Commission. The Commission was there to redefine obesity.

So I think we've accomplished a lot. And the big question now is how quickly and effectively can this be applied in the clinic to help our patients be individualized for specific diagnostic criteria and also treatment to follow when needed?