Overweight People Do Not Have A Higher Mortality Risk: Study

During the 20th century, researchers claimed that people with a higher body mass index are at a far higher risk of suffering from lifestyle diseases like diabetes, stroke, and cardiovascular disease — to name a few. And that, in turn, shortens their life expectancy. But as it turns out, that is not true after all. A new PLOS One study states that a high BMI range (over 30) by itself does not increase an individual’s mortality risk.

“Epidemiologic evidence regarding the association between BMI and mortality has been inconsistent, especially with regards to overweight and obese individuals, with some analyses demonstrating similar or lower risk of all-cause mortality,” wrote authors of the study Aayush Visaria and Soko Setoguchi from Rutgers University.

“In addition, most U.S. studies to date have used data from the 1960s through the 1990s and have included predominantly non-Hispanic White men and women. In contrast, the contemporary U.S. population has a substantially different BMI distribution, with mean BMI having risen by more than 2 kg in both men and women since the 1970s,” they added. “And has seen more than 10 year increases in life expectancy both overall and among obese individuals.”

To further investigate these data inconsistencies related to the link between BMI and all-cause mortality in the general population residing in the United States, the duo analyzed data of 554,332 adults from the 1999–2018 National Health Interview Survey (NHIS). They specifically focused on analyzing the data of men and women over 65 who belonged to different racial and ethnic groups. Their mean BMI was 27.5. Each participant had self-reported their history of cardiovascular diseases, cancers, asthma, kidney disease, and diabetes.

“Our findings have consistently shown no significantly different mortality risk for overweight-range BMI. Among younger adults, while BMI of 25–27.4 was not associated with increased mortality, there was nearly 20% higher mortality risk for young adults with a BMI of 27.5–29.9,” the researchers observed.

The duo further noted that there could be various reasons why overweight people or those with a higher BMI could have a mortality risk that was similar to those with a “normal” BMI. One reason is that overweight people who do not have any disease or co-morbidity can be metabolically healthy and have a “more favorable” body composition that has higher lean mass than someone with BMI that falls within the normal range.

Also, BMI by itself does not determine how much belly fat an individual might have. “Lean individuals who develop diseases such as hypertension or diabetes may have more aggressive or treatment-resistant disease, whereas overweight or obese individuals who develop such conditions may be able to manage or even reverse disease with weight loss strategies,” the duo warned.

“One limitation of prior U.S. studies is a lack of racial diversity and representativeness of the changing demographic landscape. Our study included >100,000 minority adults, who exhibited lower mortality risk at overweight and obese BMIs compared to non-Hispanic White adults,” they added.

But the study has its limitations. First, the participants in the NHIS data had self-reported their BMI that might have led to some misclassification. But the researchers say prior studies also used data of participants who had reported their BMI levels.