“BMI is not a reliable predictor of disease or mortality risk.”
According to a new newspaper, the Waist to waist circumference is a better predictor of healthy weight and should be considered as a better measure of early death than BMI.
Body mass index (BMI) is commonly used to determine a person’s healthy weight, with a BMI between 18.5 and 24.9 kg/m2 being considered within the healthy weight range.
Irfan Khan, a medical student at the College of Medicine and Health, University College Cork, Cork, Ireland, who conducted the study with colleagues in Canada, notes that BMI “does not take into account fat distribution.”
“It doesn’t take into account where fat is stored – whether it’s concentrated around the hips or the waist. As a result, BMI does not reliably predict disease or mortality risk.
“We wanted to find out whether waist-to-hip ratio (WHR) or fat mass index (FMI) would more reliably predict mortality across different fat distributions.”
First, the researchers looked at whether more fat (obesity) leads to, or just correlates with, higher mortality rates.
Analysis of data from UK Biobank participants with genes known to increase risk of weight gain/obesity (ie genetic obesity) showed that higher fat levels actually cause more people to die, rather than just from it to be associated.
The researchers then used information from 25,297 Caucasian men and women whose health was monitored until death as part of the UK Biobank study, and 25,297 controls from the same study who were matched for age, sex and genetic ancestry to apply genetic obesity measurements to the data. These measures included information on the genes associated with BMI, WHR and FMI. (The mean age of the participants was 61.6 years, of which 59.3% were men.)
The results showed a linear association between WHR and death from any cause, suggesting that those with the lowest WHR were least likely to die early and gradually increased as WHR increased.
In contrast, BMI and FMI had a J-shaped association with all-cause mortality, meaning that people with either an extremely high or low BMI or FMI had a higher risk of death than those with a moderate BMI or FMI.
Compared to BMI or FMI, WHR had a stronger correlation with all-cause death. For example, compared to an increase in BMI or FMI, the likelihood of early death increased about twice for every one unit increase in WHR.
Men had a stronger correlation between WHR and all-cause mortality than women.
Unlike BMI and FMI, the relationship between WHR and death from all causes was the same for people with different amounts of fat.
That Major errors in BMI, says Mr Khan, is that it ignores variations in fat distribution. This may suggest that despite the health hazards of belly fat, someone who has gained “fat around the waist” will have the same BMI as someone of the same age and height who stores fat around their hips.
However, WHR more accurately measures the amounts of abdominal fat, particularly visceral fat, which wraps around internal organs and increases the risk of a range of diseases, including type 2 diabetes and heart disease.
“With WHR, the message is simple: the lower the WHR, the lower the mortality risk.”
He also says the results need to be confirmed in people from different genetic backgrounds, but they show that whatever population was studied, it’s better to have a lower WHR.
“This is another benefit over BMI, where the optimal BMI varies from population to population,” adds Mr. Khan.
Although genetic WHR was used in the analysis, the study authors claim that their results still apply to the traditional definition of WHR.
How is Waist to Hip (WHR) calculated?
To get this quick and easy measurement, divide your waist by your hips.
They conclude that waist-to-hip ratio is a better indicator of health than body mass index.
According to Mr. Khan, clinical counseling and interventions should place more emphasis on setting appropriate WHR goals than on generic BMI goals.
“A more accurate measure of healthy body shape can make a significant difference in morbidity and death from type 2 diabetes, heart disease, some cancers and many other conditions.”
Source: EASD Stockholm 2022, Summary 65
Photo credit: Getty
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