Obesity is a term that gets used a lot, but not many people know what it actually means. The clinical definition of obesity is one that has been lacking clarity for quite some time.
Now, researchers at Van Andel Institute are seeking to redefine obesity following their discovery of two obesity subtypes. To help explain what these researchers found and why it is important, let’s explore what obesity is, how it is defined, and why that definition is in need of an update.
What is Obesity and How is it Defined?
Obesity is defined as excessive body fat that increases the risk of health problems, but what constitutes “excessive”? For years, we have relied on the Body Mass Index (BMI) to define obesity. This index takes into account an individual’s sex, weight, and height in order to classify them as either underweight, normal, overweight, or obese.
However, the problems with using BMI to define obesity have been obvious from the start. Namely, BMI doesn’t take into account important physiological differences and can thus misrepresent a person’s health status. Someone with a large amount of muscle mass such as a bodybuilder, for example, would likely be considered obese if BMI is all that you considered despite having a low percentage of body fat.
These issues with how obesity is defined and diagnosed led researchers to create a better framework for diagnosing patients with obesity.
Discovery of Two Obesity Subtypes Leads to New Obesity Definition
Using a combination of laboratory studies in mouse models and deep analysis of data from identical twins, researchers from Van Andel Institute were able to discover four metabolic subtypes that influence individual body types. Two of these newly discovered subtypes were prone to leanness, while the other two were prone to obesity. By examining the two metabolic subtypes associated with obesity, researchers were able to uncover fascinating new insights into both how obesity is defined and the various health problems that it can cause.

“Nearly two billion people worldwide are considered overweight and there are more than 600 million people with obesity, yet we have no framework for stratifying individuals according to their more precise disease etiologies,” said J. Andrew Pospisilik, Ph.D., chair of Van Andel Institute’s Department of Epigenetics and a co-author of the study. “Using a purely data-driven approach, we see for the first time that there are at least two different metabolic subtypes of obesity, each with their own physiological and molecular features that influence health. Translating these findings into a clinically usable test could help doctors provide more precise care for patients.”
One obesity subtype that researchers discovered was characterized by greater fat mass and greater lean muscle mass while the other obesity subtype was classified by greater fat mass alone. Somewhat surprisingly, it was the subtype characterized by both greater fat and lean muscle mass that was most associated with increased inflammation – an obesity risk factor that can elevate the risk of cancer and other diseases.
“Our findings in the lab almost carbon copied the human twin data. We again saw two distinct subtypes of obesity, one of which appeared to be epigenetically ‘triggerable,’ and was marked by higher lean mass and higher fat, high inflammatory signals, high insulin levels, and a strong epigenetic signature.” Pospisilik said,
By identifying these new subtypes of obesity, Pospisilik and his team are hopeful that their research will be able to help physicians develop precision medicine strategies and diagnose patients based on a much more accurate and meaningful clinical definition of obesity.
Conclusion
Obesity is something that can lead to a wide range of health problems, and it is an important issue for healthcare professionals to tackle. However, it is also important to ensure that patients are being correctly diagnosed and treated. BMI charts and their inherent flaws are far too simple to define and diagnose something as complex as obesity. Thanks to new research from Pospisilik and his team, though, a better definition and framework for diagnosis could be on the horizon.