Up to a third of people who think they’re at a healthy weight may actually be obese, one study suggests.
Israeli researchers, who examined data from 3,001 people, found that about a quarter of men and nearly four in 10 women with a “healthy” body mass index (BMI) had enough body fat to qualify as obese.
As a result, millions who don’t think their size is a concern are at risk of weight-related conditions such as type 2 diabetes, the experts warned.
They urged clinicians to scrap the commonly used BMI score when determining whether a patient is at a healthy weight in response to the “alarming” findings.
Instead, people should use devices to measure body fat percentage – priced from £20 or found in gyms. These gadgets should become the “gold standard” for exercising if someone is obese, the team argued.
Researchers in Israel, who examined data from 3,001 people, found that about a quarter of men and nearly four in 10 women with a “healthy” Body Mass Index (BMI) had so much body fat that they should be classified as obese
BMI is calculated by dividing an adult’s weight in kilograms by their height in meters squared.
It is considered the standard indicator of a person’s health, with the metric indicating whether someone is underweight, a healthy weight, overweight or obese.
But Tel Aviv University scientists, led by Professor Yftach Gepner, said the body’s fat content is the most important measure of obesity.
It is usually measured using bioelectrical impedance analysis, which uses a device to send painless electrical impulses through the body and measure resistance to them.
Results then indicate how much of the body is made up of water, such as muscle and blood, and is therefore fat-free.
Women’s body fat should be no more than 35 percent of their weight, researchers say. For men it is 25 percent.
Obesity can cause a range of life-threatening illnesses such as heart disease, fatty liver and kidney problems.
Relying solely on BMI to determine whether a person is at a healthy weight has led people to be told their weight is normal when they are actually obese, the researchers warned.
To determine how many people miscategorized the BMI metric, the researchers examined data from 3,001 Israeli women and men between the ages of 20 and 95.
They looked at BMI scores, DXA scans — an X-ray that measures body composition and fat content — and blood tests.
Results, published in the journal Limits in nutritionshow that 967 individuals were at a healthy weight, according to the BMI results.
However, of this group, 38.5 percent of women and 26.5 percent of men identified as “obese with a normal weight” because they had too much fat.
Analysis of blood samples showed that these participants had high levels of sugar, fat and cholesterol – major risk factors for type 2 diabetes, heart attacks and strokes.
In addition, according to the BMI results of the 1,056 overweight volunteers, 30 percent of the men and 10 percent of the women had a normal body fat percentage.
Professor Gepner said: ‘Our findings were somewhat alarming, indicating that normal-weight obesity is much more common in Israel than we had assumed.
‘In addition, these individuals, who fall within the norm according to the prevailing BMI index, usually pass ‘under the radar’.
“Unlike overweight people, they don’t get treatment or instructions to change their diet or lifestyle – putting them at even greater risk for cardiometabolic disease.”
The researchers concluded that body fat percentage is a more reliable indicator of an individual’s health than BMI, ostensibly to help the measure become the “prevailing health standard.”
They noted that in addition to devices that measure body fat percentage, more accessible instruments – such as skinfold measurements – could also be used. It works by measuring the thickness of the fat layer under the skin using a caliper to pinch the skin and measure the fold.
“We recommend equipping all clinics with appropriate devices to measure body fat levels, gradually making this the gold standard, both in Israel and globally, to prevent illness and early death,” they added.
The researchers noted that they did not track the health of the participants over time and that only a few markers of health were analyzed.
Medical professionals have long been aware of the shortcomings of BMI, which has come under increasing scrutiny in recent years.
For example, people who are muscular may be classified as obese by this measure if their weight is actually healthy because muscle is denser than fat.
A person’s ethnic group can also affect their risk of developing a health condition. This means that someone from a South Asian country can have a healthy BMI but have a higher risk of developing diabetes.
The statistic also doesn’t work on pregnant women.
However, measuring body fat percentage also has limitations.
Results may be affected by food and drink consumption and home devices may be less accurate than devices used in gyms and health centers.