July 12 (UPI) -- People who are obese but otherwise healthy do not have an increased rate of mortality, according to a study in Toronto -- conflicting with results of a major study in Europe.
Researchers at York University's Faculty of Health followed 54,089 men and women from five cohort studies through 2017. Participants who were otherwise healthy were compared with those with elevated glucose, blood pressure or lipids alone or another metabolic factor, including smoking status, ethnicity, age and lifestyle. Their findings were published Thursday in the journal Clinical Obesity.
"This is in contrast with most of the literature and we think this is because most studies have defined metabolic healthy obesity as having up to one metabolic risk factor," said study leader Dr. Jennifer Kuk, associate professor at the School of Kinesiology and Health Science at York University. "This is clearly problematic, as hypertension alone increases your mortality risk and past literature would have called these patients with obesity and hypertension, 'healthy.' This is likely why most studies have reported that 'healthy' obesity is still related with higher mortality risk."
In March, a study was published of 296,535 adults of white European descent between 2006 and 2010. It showed the risk of heart attacks, strokes and high blood pressure increase as body mass index increases beyond 22-23 kg/m.
The study in Canada showed that dyslipidemia, hypertension or diabetes are related with a high mortality risk, but obesity alone doesn't fit into this situation.
In the study sample, 6 percent of individuals with obesity had no other metabolic abnormalities.
In the follow-up of an average of 7.2 years, 9 percent of the patients died.
Anyone with a BMI over 30 kg/m2 should lose weight, according to current weight management guidelines.
"We're showing that individuals with metabolically healthy obesity are actually not at an elevated mortality rate. We found that a person of normal weight with no other metabolic risk factors is just as likely to die as the person with obesity and no other risk factors," Kuk said. "This means that hundreds of thousands of people in North America alone with metabolically healthy obesity will be told to lose weight when it's questionable how much benefit they'll actually receive."
The "obesity paradox" is based on research that has suggested that being overweight or even obese, particularly in the elderly, might not have an effect on deaths from heart disease. If people maintain a reasonable level of fitness, the extra weight might be protective, according to the theory.
A study published in March found that high body mass was not associated with early death. Instead more body fat -- regardless of size -- leads to a high risk of dying.
The relationship between body size and health "is more nuanced than the number on your bathroom scale," said Leslie, a professor of medicine and radiology at the University of Manitoba, in Winnipeg, Canada. "It's important to be attuned to what you're made of, rather than just how much you weigh."