How has obesity traditionally been defined?
Obesity has traditionally been measured using body mass index, or BMI. The BMI is easy because it’s weight over height squared. It’s easy to calculate. Historically, we’ve defined obesity by a BMI over 30. BMIs between 25 to 30 were considered overweight.
How does the commission recommend obesity be measured?
We’re recommending that excess adiposity should be confirmed through additional measurements such as waist circumference, waist-to-hip ratio and waist-to-height ratio to provide a more comprehensive assessment of obesity. Under some circumstances dual x-ray absorptiometry (DEXA) can be used to assess body composition including how much is adipose tissue. This approach aims to better capture the complexities of obesity as a spectrum of conditions, helping to differentiate between clinical obesity and preclinical obesity. Clinical obesity means that diseases that develop because of obesity are present, such as heart failure and obstructive sleep apnea. Preclinical obesity indicates excess body fat and potentially increased risk of health issues but without current organ dysfunction.
What’s the biggest change the commission has recommended?
Through this work, we’ve dismissed the term “overweight” and replaced it with “preclinical obesity.” Why? Because there are some overweight people who carry too much body fat, and there are people who have a BMI in the “overweight” range who have no increased body fat. And there are populations of people worldwide who have a BMI under 25 who have too much body fat. So, BMI is not an accurate measure of health, particularly in the 22-30 range. The commission is saying that we need to go beyond BMI. And the first, simple step and most accurate measure is waist circumference.
Why is the designation of “preclinical” important?
There was a lot of discussion about labeling it as “preclinical” obesity. Why not label it obesity? Why not label it nothing? Even though someone with excess body fat might not show any signs of illness or disease related directly to obesity, it’s still important for them to watch their weight, avoid gaining more and possibly lose some weight. Now that we have defined preclinical obesity, we can begin collecting data that can assist in population health studies to keep people from developing clinical obesity.
How do you anticipate this report being disseminated and implemented in practice?
This is a great question and the most difficult. The commission’s job was to create the diagnostic criteria. But in my opinion, we need to start with the 75-plus organizations that endorsed this, including the American Heart Association, the American Diabetes Association and The Obesity Society. The goal would be to have them incorporate this approach to assessing people living with obesity by using these criteria in their guidelines.
What makes addressing obesity a global priority, and how can we expect to make progress?
If the current trends continue, it is estimated that the global obesity rate will reach 51% by 2025 using BMI as the measure. It’s staggering.
In terms of making global changes, it will take time. When I give talks, I always bring up this comparison: In the 1950s, 50% of adults in the U.S. smoked. In 2024, smoking rates have dropped to 11.5%. That shift took 70 years to accomplish. The progress with smoking shows how public health efforts, though slow, can make a difference. It’s not that quick or easy, but it does happen over time.
Obesity is a major public health issue around the globe and addressing it in a more scientific way is what we’re trying to do with our commission.
What’s misunderstood about obesity?
Obesity is a complex issue involving genetics, environment and human behavior. The reductionist view, which blames individuals for their obesity, is unhelpful and oversimplifies the causes. While having excess fat historically helped us survive, today it’s leading us to serious health problems.
It's important to recognize we're not calling obesity a disease. Clinical obesity refers to illnesses or diseases that can develop as a result of obesity. While some people object to this distinction, 75 organizations worldwide have endorsed the commission's stance, recognizing that many individuals with excess body fat do not experience any associated illnesses.
What do you wish patients and their providers knew about obesity?
For patients, be sure you’re working with a healthcare professional who listens well, shows no stigma or bias regarding your body weight, and is informed about the updated guidelines for diagnosing excess body weight. Look for a physician who is objective and understands when clinical obesity and associated illnesses require treatment. When we diagnose someone with clinical obesity, we know they need treatment. Almost always weight loss is part of that treatment.
We know that due to time constraints and lack of training, many doctors struggle to conduct a comprehensive assessment, which is why organizations like The Obesity Society provide specialized training and certifications to improve care for patients with obesity.
This interview was edited for length and clarity.
