Measuring waist-hip ratio, not body mass index, is a better indicator of a healthy weight, and may better predict premature death, according to a new study. Photo by PublicDomainPictures/Pixabay
Sept. 21 (UPI) — New research suggests that waist-hip ratio, not body mass index, is a better measure of healthy weight, and may predict premature death better than BMI.
The researchers urge using the new method to replace BMI, which the Centers for Disease Control and Prevention has called “an inexpensive and easy tool” because that calculation requires only a person’s height and weight.
But the researchers said waist-hip ratio is also a “quick and easy measure,” calculated by dividing waist circumference by hip circumference.
Their work is being presented this week at the annual meeting of the European Association for the Study of Diabetes in Stockholm.
BMI is calculated by taking a person’s weight in kilograms and dividing it by the square of height in meters, with a BMI of 18.5 to 24.9 considered healthy. But this measure doesn’t take into account fat distribution, the researchers said.
“It doesn’t take into account where fat is stored, whether it accumulates around the hips or waist. As a result, BMI doesn’t reliably predict disease risk or mortality,” said Irfan Khan, a medical student at the University College Corks. Cork School of Medicine and Health, Ireland, who carried out the research with colleagues in Canada.
This means that a person who has accumulated fat around the waist will have the same BMI as someone of the same age and height who stores fat around the hips, despite the health risks of belly fat, the researchers said.
Khan said waist-to-hip ratio better reflects levels of abdominal fat, including visceral fat, which surrounds organs inside the body and increases the risk of a variety of medical conditions.
A more accurate measurement of healthy body shape “can make a significant difference in ill health and deaths from type 2 diabetes, heart disease, some cancers and many other conditions,” he said.
According to Khan, the message is simple: the lower a person’s waist-to-hip ratio, the lower their mortality risk.
Waist-hip ratio is “a stronger and more robust measure” compared to BMI, he told UPI in an email.
“Instead of aiming for a specific BMI target, which may or may not be beneficial depending on your individual body composition, aim for a lower BMI [waist-to-hip ratio] will always lead to a lower death rate,” he said.
Initially, the researchers wanted to determine whether waist-hip ratio, or fat mass index, would more reliably predict mortality at different fat distributions.
Fat mass index is calculated by dividing fat weight in kilograms by height in meters squared; The BMI considers the total weight of a person in the measurement.
First, the study researchers analyzed data from UK Biobank participants who had genes known to predispose them to weight gain and obesity. Their analysis indicated that higher levels of fat caused higher mortality, rather than simply being correlated with it, according to the release.
They then applied information about the genes associated with the three measures — BMI, waist-hip ratio, and fat mass index — to data from approximately 25,000 white men and women whose health had been monitored as part of the UK Biobank study. until his death, and a similar number of controls “matched for age, sex, and genetic ancestry.”
Despite using the genetically determined waist-to-hip ratio for their analysis, the scientists said their findings apply equally to the conventional measurement of waist and hips.
The researchers found that the risk of premature death was lowest for those with the lowest waist-to-hip ratio and then increased steadily with increasing waist-to-hip ratio.
In contrast, people with extremely high or low BMI or fat mass index had a higher risk of death compared with those with moderate BMI or fat mass index.
For example, each unit increase in waist-hip ratio increased the odds of premature death by almost twice as much as a one-unit increase in BMI or fat mass index.
The scientists also found that waist-hip ratio was more strongly associated with death from all causes than BMI or fat mass index. This link was stronger in men than in women.
According to Khan, doctors may already have a tape measure for certain exams: like measuring the apparent versus actual length of a patient’s limbs, or measuring the length of the liver during abdominal or gastrointestinal exams.
“Waist and hip circumference are easy to measure in adults with the tape measure, so I don’t see why doctors shouldn’t carry a tape measure to do this as well,” he said.