Obesity alone does not increase risk of death

The results of this study could impact how we think about obesity and health, says Jennifer Kuk, associate professor at the School of Kinesiology and Health Science, who led the research team at York University.

"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," says Kuk. "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."

Kuk's study showed that unlike dyslipidemia, hypertension or diabetes alone, which are related with a high mortality risk, this isn't the case for obesity alone.

The study followed 54,089 men and women from five cohort studies who were categorized as having obesity alone or clustered with a metabolic factor, or elevated glucose, blood pressure or lipids alone or clustered with obesity or another metabolic factor. Researchers looked at how many people within each group died as compared to those within the normal weight population with no metabolic risk factors.

Current weight management guidelines suggest that anyone with a BMI over 30 kg/m2 should lose weight. This implies that if you have obesity, even without any other risk factors, it makes you unhealthy. Researchers found that 1 out of 20 individuals with obesity had no other metabolic abnormalities.

"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," says Kuk. "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."

1. J. L. Kuk, M. Rotondi, X. Sui, S. N. Blair, C. I. Ardern. Individuals with obesity but no other metabolic risk factors are not at significantly elevated all-cause mortality risk in men and women. Clinical Obesity, 2018; DOI: 10.1111/cob.12263