2024-09-14 05:31:15
The body mass index helps you quickly calculate your own weight. For some time now, however, doubts have been growing about its importance. Researchers propose alternative measurements that reveal more about health — and body fat percentage.
Height and weight in one click: that’s all you need to calculate your body mass index (BMI). The scale indicates whether someone is underweight, normal weight, overweight or obese and has been doing so for 200 years. But there is a contradiction of the established index.
The number of overweight people is increasing worldwide. According to the Federal Statistical Office bring 2019 around Half of all German adults are overweight. So the Federal Republic is little more than the EU average. In addition, studies show that many overweight children and young people carry extra kilos with them into adulthood.
But when does someone become obese? BMI is often used to answer this question. “In practice, BMI is often used because it is easy to obtain and has an important level in assessing nutritional status,” says Geraldine de Heer, deputy clinical director of the Clinic for Intensive Care Medicine and head of nutrition group at the University Hospital Hamburg-Eppendorf (UKE).
Nowadays you can get your body mass index (BMI for short) for free just a few clicks online calculate and evaluate, for example on the websites of health insurance companies.
To find your BMI, divide your body weight in kilograms by your height in meters squared. The result provides information about the deviation of a person’s weight from the value considered normal for their height.
The procedure is standardized for children, although their BMI is not compared with fixed thresholds for underweight and overweight, but rather with percentages for people of the same age and gender. A percentage shows how a value compares to other values in a group. For example, if a child is in the 25th percentile for BMI, it means that 25 percent of children in his age and gender group have a lower BMI than the child.
First index from 1832
According to the World Health Organization (WHO), BMI values in adults are divided as follows:
BMI less than 18.5 – underweight
between 18.5 and 24.9 – normal weight
between 25.0 and 29.9 – overweight
between 30.0 and 34.9 – grade I obesity
between 35.0 and 39.9 – grade II obesity
over 40 – obesity grade III (also called permagna obesity)
BMI says more about a person than body weight, says de Heer: The value can be useful for the first estimate. “BMI determination can help ordinary people develop an awareness of their nutritional status,” he emphasized.
After World War II, practitioners discovered that their obese clients had increased mortality rates, described a 2008 summary in the journal Nephrology Dialysis Transplantation. published. Thus, we conducted an intensive search for a key figure that could be used to describe body weight.
To calculate this, an index developed by the Belgian scientist Adolphe Quetelet is used. In 1832, Quetelet found that weight increases with the square of height – except for growth spurts after birth and during puberty. In 1972 the Quetelet index was renamed the body mass index.
But while BMI is used as a measure of overweight and obesity in many health guidelines, there are still many critics who point out its limitations.
The main weakness of BMI is that it doesn’t take body composition into account, so it doesn’t differentiate between muscle and fat, says de Heer. “This can lead to inaccurate estimates of nutritional status if we use BMI as the only method.” is considered particularly harmful.
Outliers in height can influence BMI: For example, a two-meter-tall female basketball player with high muscle mass and low body fat may be considered overweight based on her BMI, even if can be classified as completely healthy depending on it. food situation. Similarly, for an elderly or very sick person with low muscle mass, a BMI at a normal weight may indicate a healthy diet.
Differences in the body have an effect
The body is made up of different proportions of fat and muscle, with muscle having more weight than muscle. This means that BMI can be inaccurate for people with a lot of muscle mass.
According to Yurdagül Zopf from the University Hospital of Erlangen, this only affects a few cases – there are not many people with a high BMI and pure muscle mass. “So if someone gains weight, doesn’t do any exercise and obviously doesn’t look like Arnold Schwarzenegger, then what they’re gaining is fat and not muscle,” emphasizes nutritionist Zopf.
Another point of criticism about BMI: A study in the journal “International Journal of Obesity” examined the relationship between body fat percentage and BMI in three different groups in Singapore in 2000. Using data from 300 adults with roots in China, Malaysia and India, the study showed that the relationship between body fat percentage and BMI differed significantly between the three groups.
The research team also compared the results with reference values, which are based on data from white, Western people – here too, big differences became clear. According to the study, with the same amount of body fat, a Western person has a BMI of 30, a Chinese person has a BMI of 27 and a Malaysian person has a BMI of 26.
The study attributed this to differences in body composition. If obesity is viewed as an excess of body fat rather than excess weight, obesity thresholds in Singapore based on BMI need to be lowered, the study concluded.
Alternatives to BMI
BMI is not the only way to determine body condition. Other options include fat mass index (FMI) and hip-ratio (WHR). A study, the results of which were published in the journal “JAMA Open Network” in 2023, examined which of these values is the most. most powerful with death connected.
Using data from 388,000 British adults, a team led by doctor Irfan Khan found that the connection with the risk of death is the strongest for the abdominal segment – so it should receive special attention in health measures. Due to known limitations, it is unclear which BMI value is associated with the lowest risk of death, according to the study.
There is one more in 2023 Business journal “Plos One”. A published US study concluded that BMI alone does not increase the risk of death. Based on data from half a million American adults, a research group led by Rutgers University showed that the association between BMI and mortality may vary by age and appears to be linked to other risk factors. “Our study highlights the growing reservations of using BMI alone as a basis for clinical decisions,” the study authors concluded.
In view of the increasing prevalence of obesity worldwide, nutritionist Geraldine de Heer recommends sticking to established norms. “It should make us think about how we deal with food and exercise, especially with children, and try for a change in direction.”
According to some experts, education about obesity falls short. “On average, it takes six years for a doctor to refer a patient to obesity,” Yurdagül Zopf emphasized. This is worrisome because the disease is associated with increased levels of inflammation in the body and a higher risk of cardiovascular disease and certain types of cancer.
“BMI is a very important component for this,” said Zopf, who heads the Hector Center for Nutrition, Exercise and Sports. “I would see it as a guarantee that everyone would have information about what BMI is.”
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