One billion people worldwide are considered overweight or obese. In this country, it affects about one in four adults. But do all affected individuals therefore experience symptoms of illness and die earlier? No.
For several years now, the so-called Body-Mass-Index—BMI for short—has been under criticism. Until now, the value was determined with a simple calculation to classify underweight or overweight. But what does body weight actually say about a person’s health?
An international commission (Commission on Clinical Obesity) of 56 experts developed new definitions of obesity this year and recommends a changed approach to diagnosis. The aim is to provide more targeted help to severely overweight individuals while at the same time reducing misdiagnoses and overtreatment. In addition, the experts hope this will lead to the destigmatization of affected individuals in society.
How useful is the BMI calculator today?
Online, countless websites invite users to calculate their own BMI. The simple formula is: weight in kilograms divided by height in meters squared. A value below 18.5 kg/m2 indicates underweight, overweight begins at 25 kg/m2, and values above 30 kg/m2 have so far been classified as obesity. A BMI of 40 kg/m2 or more is categorized as grade III obesity.
However, these figures say nothing about body fat percentage or muscle mass. People with high muscle mass may be wrongly classified as overweight. Moreover, some individuals with higher body weight show no symptoms of illness, whereas those at a “normal weight” with risky fat distribution often go unnoticed, since it doesn’t show up in BMI.
Thus, the BMI does not allow conclusions about an individual’s health status. This has led in the past to misdiagnoses, unnecessary risks, and costs. Medical resources have been consumed—without any benefit to patients.
Other decisive factors in body composition include age, sex, and ethnic differences, none of which are considered in BMI calculation. For example, in Asia the obesity threshold is already 27.5 kg/m2, since the population is on average shorter than in other parts of the world. However, height differences are slowly converging globally.
An optimized obesity diagnosis, according to the commission, should primarily benefit patients and relieve the healthcare system.
The role of visceral fat
To better assess the risk of secondary diseases linked to excess body weight, physicians focus on the distribution of visceral fat, i.e., the fat stored in the abdominal cavity around the organs. To a certain degree, fat deposits in this area are normal and healthy, but beyond that point they are a significant risk factor for cardiovascular disease and type 2 diabetes.
If BMI is used as the sole measurement, excess visceral fat can easily go unnoticed.
New specification of obesity
The international commission therefore agreed on new classifications of obesity in its report:
Clinical obesity
This term describes obesity in which a chronic illness exists because the excess weight has already caused organ dysfunction. Clinical obesity is regarded as a progressive disease that, over time, can lead to severe end-organ dysfunction and life-shortening complications.
In such cases, rapid and targeted medical care is crucial.
Preclinical obesity
This type is not considered a persistent disease, as no organ dysfunctions are yet detectable. Here, there is only an elevated health risk that can be reduced through preventive measures and careful counseling.
To provide an individual diagnosis—which is the commission’s main concern—other parameters must be examined, not just BMI.
“A thorough and balanced definition of obesity is long overdue to address the medical and socioeconomic challenges,” explains Prof. Stefan Richard Bornstein, member of the commission, director of the Center for Internal Medicine at University Hospital Carl Gustav Carus Dresden, and researcher at the German Center for Diabetes Research (DZD).
Step by step to an individual diagnosis
The experts recommend a multi-phase diagnostic process for clinical obesity. The first step involves medical history and a physical examination. This should be followed by a series of standard laboratory tests, including a complete blood count, blood sugar measurements, a lipid profile, as well as kidney and liver function tests. Additional diagnostic tests may follow if necessary.
In the end, the experts presented 18 criteria for identifying clinical obesity. These include signs of organ or tissue dysfunction as well as severe daily life restrictions caused by excess weight. Parameters include high blood pressure, lymphedema, shortness of breath, and more.
Modern alternatives to BMI
So, is the BMI calculator still useful at all? As an initial indicator for a possible condition and for triggering further tests, the Body Mass Index can still be relevant today—particularly when values exceed 40 kg/m2, since obesity at this level almost always carries severe health consequences.
Modern alternatives for better assessing health status include bioelectrical impedance analysis and the waist-to-hip ratio.
Bioelectrical Impedance Analysis (BIA)
This test can, within minutes and without pain, determine a person’s body fat percentage, muscle mass, and water content. Downsides: The devices are relatively expensive, and results may vary depending on stomach contents. Therefore, no meals should be consumed before the test.
Waist-to-Hip Ratio (WHR)
This very simple method compares the ratio of waist circumference to hip circumference. Both are measured with a tape measure, and the waist value is divided by the hip value. This method provides a good estimate of visceral fat.
Conclusion
The BMI calculator is insufficient for obesity diagnosis, since its values cannot reflect an individual’s health. According to the commission, a distinction should be made between chronic disease with organ dysfunction and obesity as only a risk factor for secondary diseases without current impairment.
With a set of diagnostic criteria, the international commission seeks to make it easier to identify clinical obesity requiring immediate treatment. In cases of preclinical obesity, counseling and, if needed, further preventive measures are recommended.
By making this distinction, experts hope to improve patient outcomes more quickly, relieve the healthcare system by reducing misdiagnoses, and protect individuals from unnecessary risks.
If you are overweight and want clarity about your health status, reach out to obesity centers.
Sources
- https://www.dzd-ev.de/presse/pressemitteilungen/pressemitteilungen-2025/internationale-kommission-schlaegt-umfassende-ueberarbeitun/index.html
- https://herzmedizin.de/fuer-aerzte-und-fachpersonal/kardiologie-interdisziplinaer/herz-und-diabetes/neue-kriterien-diagnose-klinische-adipositas.html
- https://www.swr.de/wissen/neues-verfahren-zur-definition-und-diagnose-von-adipositas-uebergewicht-100.html
- https://www.aerztezeitung.de/Medizin/Adipositas-Diagnose-BMI-bald-Geschichte-455775.html
- https://www.stern.de/gesundheit/ernaehrung/bmi-und-uebergewicht-warum-der-body-mass-index-ueberholt-ist-3796626.html#:~:text=So%20kann%20ein%20trainierter%20Sportler%20wegen%20seines,die%20Wahrscheinlichkeit%2C%20krank%20zu%20werden%2C%20stark%20beeinflussen.u
